Thursday, December 18, 2008

Single Set Point Temperature Controller

This is a generic or standard controller for any type of process. Shown here is a temperature controller.Temperature Controller

The STC1000 could be used for Ovens or furnaces, liquid baths, heating or environment chambers. It has a single analog input and an analog or relay output.

Analog inputs could be like 4-20 mA, thermocouple or RTD. Analog outputs can be 0-10 V for a thyristor drive, SSR drive output or potential free contacts of a relay to operate external 3 phase contacters.

The closed loop control could be On-Off or Time-Proportional. It was known as digital temperature indicating controller. Sometimes it would be used just as a Alarm or in a Trip circuit for protecting a system, when a uP or uC based PID controller fails.

This is used in the processing of plastics, rubber, metals and in chemical plants too. Here is a checklist that was made for helping its fabrication. You can see the limitations in which we manufactured these products. An optimum quality was evolved, defined by a user's affordability of the product.

Production Checklist of STC1000

  1. Has Transformer been soldered properly with reinforced pads - Scrape with blade area around pad and make lead bridges to support transformer.Front Card and Rear Card must have very thick solder bridges after fixing sq. post.
  2. Is the Front and back stickers and SL. No Sticker properly stuck - In Front Sticker the holes for switch, pot LED etc. must be without Burrs file and improve. Acrylic should not have cynoacralate stains. In the back sticker there should not be any wrinkles use rubber solution (fevibond) to stick properly.
  3. Are all the Threaded parts and Plastic parts fixed with fevibond - Use Fevibond (very little) for the CJ box in rear panel all Metal screws and loose mechanical parts in Pots, plastic threads and pillars. This prevents parts from breaking loose during transportation or vibrations, All Nuts / Bolts fix tightly .
  4. Are all the Pots. Turning freely and is direction proper - Clockwise is always increment or increase in a parameter and anti-clockwise is decrement of any control or parameter. All pots should turn without friction.
  5. Are all the Front panel components Fixed properly - All Four Displays are required Fourth is for Overrange and Polarity. LED's are for Load On or Process on and Should be neatly visible above sticker and Switch should not get stuck after cabinet is closed and screwed.
  6. Only two screws must be visible on the back panel - Cover Pot clamp screw, card fixing screw etc. by Black insulation tape.Use Ni. plated Phillips / Universal head Screws for fixing back plate.
  7. Are all other items in the final packing - Check by fixing both side clamps and file if required add Instruction manual in Cover or with Invoice and DC.
  8. Sources of omissions and neglect checked by Visual Inspection - Gnd to Earth Capacitor to be added 0.01uF 103 1kV, Relay OEN only, Polarity of Electrolytic and diodes , Regulator tab touching any conductor, Loose wire strands, Solder Bridges absent at places where it is required.
  9. Troubleshooting when a card does not work - Keep always a 3D reference of a working unit / card compare component to component by visual inspection wrong polarity of diodes / Tx / IC, wrong value of Resistor or Low value capacitors missing jumpers solder bridges or hairline shorts at edge of board or pad to pad lead streaks.

Saturday, December 13, 2008

Capacitor Temperature Monitor

When placing sensors in high pressure or vacuum chamber, they should be terminated by an epoxy sealed terminal block interface on the system. 4 wire RTD is best for such applications, as multiple terminations and junctions are involved; also the wires may have to run some distance.

When measuring temperature in a big surface or object, use multiple sensors. An indicating scanner-controller can be used or ensure cooling-heating is uniform using fluids or air circulation.

Zoom Image

Cooling Controller

RTD Sensors to Terminal Block Connections

W - is White Wire from RTD, R - is Red Wire from RTD, Color of Wire on RTD Sensor Pt-100.
Top 3 Terminals are for RTD 1 (Red), Bottom 3 Terms. are for RTD 2 (Yel), Marked with Color Tape.

The RTD two whites go to one end of the Platinum 100 ohms resistive sensor, the red goes to other end. The red in this sensor goes to gnd of opamp circuit in controller. Thru one white a 1mA current is injected, the other white gives a voltage output to opamp. This voltage after offset and calibration is proportional to temperature.

Tuesday, November 11, 2008

Two Stage Sequential Timer Docs

The circuit is a two stage sequential timer with auto reset. It can turn a Solenoid On/Off after a Sequence of delays that are preset. This is also a basic example of timer usage in automation.

Design Documents
Source Files Orcad Format
All Timers are 1 - 30 Secs Analog with Presets to adjust with a screwdriver. The Switch, Solenoids and Power supply has to be via terminal blocks or plug-jacks. The PCB may be upto six Square Inches for standard DIP components but with SMD it may be smaller.

Block Diagram :

Sequential Timer Specs

The PCB has to be tested to conform with the circuit, this has to be Meticulous. The Circuit is for the Battery and Solenoid Specified and will have to be modified if battery and solenoid are different. D1 to D4 can be replaced by a 300V 3A Bridge Rectifier Module. F1 fuse could be 2A - 3A Slow Blow depends on Solenoid inrush current. Presets can be with some graduations if possible for ease of adjustments. LED resistors can be a bit lower if more brightness is required.

Monday, November 10, 2008

Four Channel Temperature Alarm Docs

The temperature in a pipe is monitored with four RTD Pt-100 Sensors, The type of probe could be Extruder RTD probes with Bayonet or Compression Fitting, Get it from Omega. To keep costs low you can choose small thin film RTD sensors, they will be fast but on rough usage may break.

Design Documents
Source Files Orcad Format
The time taken to measure the temperature at the 4 points will be less than 4 seconds. An optional display of the measured temperature as shown above can be avoided by using a DMM to adjust the setpoint.

The Analog Timer Module can be set from 0- 30 minutes. If out-a remains high even after set time a out-b alarm goes on to sound a buzzer and flash a LED light.

Block Diagram :

Four Channel Temperature Alarm

It all started with a email from a client like this ..........

"I am looking at an idea for a circuit design; The idea is to sense a temp of 130 degrees and then light an LED and start a timer delay. The delay would be 3 min, after the delay if the temp is still above 130 sound alarm.

With the LED I would like to drive a counter display to show how many times the temp was sensed. I would like powered by 120vac and a 9 volt battery backup for counter circuit. If you can assist please let me know."

Saturday, November 01, 2008

Connection Diagram of AC Control SSR

This is an Application note i used to give with my ssr - app011.pdf -
SSR or Solid State Relay or Electronic Relay
This is a Thyristor Based Normally Open 230V Switch that can be turned on / off at a fast rate. This switches at Zero Crossover .Built In Snubber reduces EMI and protects the SSR. USE SAME PHASE FOR I/P & O/P.
AC-AC SSR Wiring
  • No moving parts hence no wear and tear.
  • Dissipates Heat when in On Condition.
  • Use adequate Heat Sink or SSR will fail. ( 10g / Amp)
  • Dissipation is 1.5 Watts per Amp thru Load.
  • Input to Output is optically isolated 2kV.
  • This one is AC 230V Control AC 230V N.O. Output.
  • Off state snubber Leakage is around 5 mA.
Notes -
The Termination's of High Current Lines going to Load must be very tight and crimped. Loose contacts will Spark and cause Fire.
Fuse Rating of HRC Fuse - High Rupture Capacity (HRC) Fuse is Safe and Reliable. 5kW Heater at 230V is 5,000 / 230 in Amps of Fuse Rating.

Saturday, October 04, 2008

Two Setpoint Temperature Controller

A Two Point Process Controller or Temperature Controller would look like this. When a High-Low Alarm Protection for uC based Controller was needed the same was modified and used.

Sometimes uC based instruments just forget and that can be costly, the watchdog timer has solved this problem. In Industrial Process Control we cannot take any chances, so a two tier or even three tier protection is required, especially so if the Job or Raw material being processed is expensive. So Real Time Analog Trip + uC Controller is safe. Then you can still have Electro Mechanical Devices for Extra protection against Fire or Meltdown.

Two Setpoint Temperature Controller

Temperature is the most common process parameter, Pressure seems to be next. Flow, Level, RPM, Distance and many more follow.

When a physical parameter let us say distance is measured, we first need a sensor that converts it into electrical values, digital or analog. The sensor used for length is a Linear encoder and it creates the electrical information for the DRO to Display.

Now many sensors like a strain gauge produce very low and weak signals and some are non-linear. So the signals undergo Amplifying, Temperature compensation and Linearizing together called Signal Conditioning. This stage outputs some standard values like 4-20mA, 0-10 V, 1-5V, or even directly digital or wireless in the new technologies. Even when a digital interfacing standard is used, amplification and some signal conditioning is required at sensor end. Compensation and Linearizing can be better done with a uC using Math or Look up Tables.

When you have many different parameters then it is better to use process controllers with a 4-20mA input standard. Then the inventory of controllers can be reused for any process.

It is always better to use sensor-end transmitters to get 4-20mA to your Controller, Recorder or SCADA System.Weak signals are corrupted by noise and dont travel long wire distance. Junction EMF at joints and terminal blocks add to errors. These are overcome by the 4-20mA signal that has the juice and punch to transmit the data over the shop floor to the control panel rooms.

Read more here Temperature Measurement and Control

Thursday, October 02, 2008

Temperature Controller for Cooling Chamber

This is part of an user manual i used to give for cooling controllers - app007.pdf

Cooling Controller

Before you use a Controller to Cool a Chamber to Say +5 Deg C.

First :

Do not Connect the Controller. Directly Connect the Cooling Device e. g. : Compressor. to the system and check the maximum cooling it can produce. In case temperature goes to 0 deg or -10 deg then by using a STC1000 you can control at +5 deg.

But if directly you get cooling of only upto +10 deg then it is impossible for any controller to produce extra cooling, in such a case as this use a better compressor or more insulation.

Second :

Connect Sensor properly and replace when broken keep sensor close to the source of cooling.

Third :

Deadband (DB) at minimum is 1 Deg this is the best setting, maximum setting of deadband may increase compressor life and also save power but will produce a huge variation in temperature.

Fourth :

If large Variation of temperature is present and you need accurate control Reduce deadband to min.

Unit is factory set db at 1 deg, remove seal tape before dead band adjustment.

Wednesday, October 01, 2008

Temperature Control in Plastic Injection Molding

This is an Application note i used to give with my controllers - app009.pdf
Temperature Control in Plastic Injection Molding.
Temperature Control
Terms in Process Control and Explanation.
There are three Controls to be Adjusted to make a Proportional temperature Controller Perform Properly. This method has to be practiced and experience gained from it can be used to get very good and stable Control of the temperature or other process parameters.
1. Set Point. (SP) -

This is the Temperature at which you require the Heated area to be. Here we have to remember it is better to control the temperature of the metallic area closest to heater to avoid thermal Cushions. In Rubber and Plastic Molding if you are measuring the plastic temperature directly it may give rise to oscillations and proper control may not be possible.

In Controlling the Temperature of Air or Water (Bad Conductors of Heat) Forced Convection with Fans for Air or Stirrers for Liquids can be used when Sensing temperature of the Liquid or air directly. But in Plastic such things cant be done as it is a semi-solid when heated hence. Control of Temperature of the Metal Discharging Heat to the Plastic is most practical. Oscillations are inevitable if the sensor is away from heater or is in contact with a non-conductor of heat. Temperature Control Curve

2. Process Value. (PV) -

This is the Temperature at the Tip of the sensor or the material touching the tip of the sensor. In Non-Conductors of Heat like plastic if we are monitoring plastic at a certain point the temperature of the plastic will be very different at various points depending on the Distance of the Heater from that point due to thermal gradients.

3. Proportional Band or Dead band. (PB) -
Dead band or H % or Hysteresis are terms used in on / off Controllers in proportional controller we use the term proportional band.

The Temperature zone in which the Controller turns on or off The heaters in a time proportional manner is the proportional Band. Set Point 200 deg C It is Given in % e.g. 10% PB of 200 deg SP is 20 deg. the Heaters are on till 190 deg C and off above 210 deg. C. Between 190 to 210 is the PB. A little above 190 the Heaters are on for 90% time. A little below 210 Deg C the Heaters are on for 10% of the time. When SP=PV Process Value the Heaters are on for 50% of the time i.e. 50% Duty Cycle.
4. Cycle Time -
This is the repetitive rate at which the heaters are Turned on or off Room Temperature 26 deg C For a Cycle time of 12 Seconds, when PV=SP heaters are on for 5 seconds and off for 5 seconds and this goes on as long as PV=SP.
Tuning or Adjusting a Proportional Temperature Controller.
Step # 1 -
Ensure Sensor is properly connected to the Temperature Controller TC polarity reversal will show reducing reading in the Display as heat builds up. The Heaters used and wattage selected must be able to bring the temperature more than the maximum required control temperature with TC. If Supply Voltage is down or heaters are blown or not in contact TC can not solve the problem.

So when in doubt connect heaters directly to supply (without TC) and see observe maximum temperature e. g. if max. temp. is 500 deg C the TC can control temperature upto 480 deg C.

Step # 2 -

Keep PB in minimum position and power on system e. g. set temperature is 300 deg C. Now Observe maximum overshoot. and adjust proportional band as in table below.

SP 300 deg C

PV (Process Value or Measured Temperature)
PV overshoot Proportional Band
10 % 330 deg C or more Near Maximum fully clockwise till end.
5 % 315 deg C to 360 deg C Middle of the PB Control or towards max.
2% 306 deg C Little above present setting.
Less than 300 deg Droop e. g. 290 PB is Critically set Do not Change.

After each change turn on system again to see response till 2 % or less variation or overshoot or oscillations are obtained.

Thumb Rule ! -
  • Increment PB to Decrease Overshoot.
  • Increment PB to Decrease Oscillations.
  • Stop adjustment when PV droops < SP
  • Adjust EC to match SP = PV after PV is stable at a point less than SP.
Step # 3 -

There is an additional control called Error Cal EC ( manual reset or Integral) which is factory set for SP=PV 50% duty cycle. In certain cases after stable reading is obtained after adjusting or tuning PB the temperature may stabilize say at 290 deg for a set point of 300 deg the process is stable but a ten degrees process error is present. this can be compensated in two ways.
a. Increase setpoint to 310 deg the process settles at 300 deg but this may not satisfactory even if it is practical.
b. Adjust Error Cal provided in the back panel to increase temperature to 300 deg from 290 deg.
When this is done give some time for system to respond after every 1/2 a turn 180 deg of the control. the EC control is a Ten turn potentiometer like the SP potentiometer after 10 turns the direction of turning must change. Clockwise Increase temperature Anticlockwise decrease temperature. (at min. PB setting EC pot sets the On/Off Operating Point).
Temperature Control using SSR and STC1000PK.
SSR Heat Control
Mains Circuit -
Always Connect Phase to Live "L ", This Can Be "R" in a RYB System 3 Phase . "L" Live Can Be Verified by a "Neon Tester" . and it is the Energy Line (Tester Glows). "N" Neutral is the Energy return line and will be close to Earth Potential in a Neon tester it will not show a Glow. Earth "E" is the Local Earth at the site of the installation. ( "N" to "E" AC Voltage should be less than 5 Volts ideally)
SSR or Solid State Relay or Electronic Relay -

Generally this is a Thyristor Based Normally Open 230V Switch that can be turned on/off at a fast rate.
  • No moving parts hence no wear and tear.
  • Dissipates Heat when in On Condition.
  • Use adequate Heat Sink or SSR will fail.
  • Input to Output is optically isolated. very tight and crimped.
  • The one used here is DC Control AC 230V 15A Load SSR.
Components and Points -
  • Connect Power From Lighting (5 A) for Controller.
  • 1 Phase 230V Supply With Earth
  • Stainless Steel Braided (SSB) Sensor "K" Type ( SSB is Earthed )
  • Heater 1 kW and 15 Amps SSR
Fuse Rating of a HRC Fuse -

High Rupture Capacity (HRC) Fuse is Safe and Reliable. 10KW Heater at 230V is 10,000 / 230 in Amps of Fuse Rating. i.e. Watts = Volts x Amps hence use
50 Amps Fuse.
Relay Terminology -
  • C Common is connected to NC when Relay is off.
  • NO Normally Open is Disconnected when Relay off. (connected to C when Relay on).
  • NC Normally Closed is Connected to C when Relay off. (disconnected when relay on).
Relay outputs are Potential Free or Floating or at High Impedance.

Note - The Terminations of High Current Lines going to Heater must be very tight and crimped. Loose contacts will Spark and cause Fire.

Monday, September 08, 2008

Connection Diagram of DC PCB SSR

This is an Application note i used to give with my ssr - app012.pdf
Diagram of SSR 5000 DC 3-30 Control / 230V AC N.O. @ 3A.
This is a Thyristor Based Normally Open 230V Switch that can be turned on / off at a fast rate. This switches at Zero Crossover . Use 5V DC for Best Results.
PCB SSR Wiring
  • No moving parts hence no wear and tear.
  • Dissipates Heat when in On Condition 5 Watts @ 3 Amps.
  • Mount with adequate Air Ventilation for 3 Amps.
  • Dissipation is 1.4 Watts per Amp thru Load.
  • Input to Output is optically isolated 1kV.
  • This one is DC 3-30 Control AC 230V N.O. Output.
  • Off state snubber Leakage is around 1 mA.
Notes -
The Termination's of High Current Lines going to Load must be very tight and crimped. Loose contacts will Spark and cause Fire.
Fast Blow Fuse is to be used. Use a 2 Amps Fuse with Holder in the Hot Line.

Electronic Shift Monitor

The Security Guard duty monitor below, shown in eight circuits at Digital Circuits - 1 are examples of logic circuits, i have converted them from the DOS Orcad to Orcad 9 and corrected some errors a few years back.

Electronic Shift Monitor - delabs

These circuits can be used for looking at the logic blocks or to learn. This product was built and sold to some firms many years back. Now these designs are best done with a PIC or Atmel chip. Here is the user manual

This circuit was done with CMOS CD40xx type of ICs. A RAM was used to store the Day/Time LED Status.

It was to monitor the Alertness of the Security Guard. Periodically the Unit will Buzz and Flash and the Security Guard has to press a Big Button to indicate he is awake, alert, agile and around the Unit.

All Green means fine, few Red LEDs means the Guard was sleeping or gone away from some times. All Red means Security Guard is missing. :-)

Thursday, July 31, 2008

Build your own Meters and Instruments

These are basic measuring circuits you can build for your home lab.

I have documented a lab DMM i had built for my use many years ago. the circuits may have errors, build it only if you understand.

Analog Dial AVO Amps-Volts-Ohms meter

This was designed, keeping in mind, that sometimes we have few components available and we could be flat broke. Even that you could not carry your DMM somewhere, but you have to make some instrument for a quick need with what is available. If you are out of cash or feel like Robinson Crusoe, then this is a low cost measurement system. I designed it to practice on eagle, i am not sure how this circuit may work, it is not tested . But i have built, repaired and designed many DMMs. So there is a fair chance, parts of it may work :~) - Low cost Dial AVO meter

Auto ranging 4-1/2 digit digital voltmeter using ICL7135 of Intersil.

Tuesday, July 01, 2008

Temperature Measurement and Control

These are documents and circuits which will help learn Basic Temperature closed loop control, There are many ways to control temperature.

  • ON-OFF Hysteresis or Dead Band Control.
  • Proportional Control with Reset.
  • Full PID Control, Manual and Auto Tune.

The first one is an electronic emulation of Thermostat or Electro-Mechanical Controls. The second is a Time-Proportional like a slow PWM. The third is the complete adaptive control.

While the first is like a limit switch, the second works like a SMPS, the third PID takes into account the speed of the process and dynamic changes or disturbances of the system and compensates in real time.

Example - In a Oven, one batch may have 100 metal boxes to heat, the second batch may have 10 boxes, the door may be frequently opened and the mains power (heater) may be fluctuating. A system that is able to adapt to these changes, without much readjustments is the objective of an ideal process control. The Accuracy and the Energy efficiency being the most important.

Process control Application notes

  • Temperature control in plastic injection molding
  • Cooling Temperature Control
  • Capacitor Temperature Monitor


Monday, June 02, 2008

EMI RFI Mains Power Filters

EMI RFI Noise Filters are required in two situations, to prevent EMI from an Electronic Equipment Like A Dimmer, Thyristor Drive, SMPS or Switcher affecting other Modules in a System or Neighboring Equipment.

The Second Situation is when a Sensitive Equipment Like a Medical Apparatus or Precision Measuring Instrument has to be Immune to any Noise from outside, as it can affect performance.

Sometimes it is Accuracy that can get affected, but some electrical jolts can damage or desensitize fine sensors or positioning systems.

EMI RFI Mains Power Filters

Filters are is connected in series with an Existing Mains Chord. It can also be Fixed in a Control Panel with a Clamp. The two X caps have higher Capacitance Value. The Y cap is Lower Value and withstands around 1kV,  It is better if X cap is AC 440V.

The common mode filter design in such a way that it cancels the noise. The correct winding polarity or direction is important for noise cancellation.

Related Resources

eEngineer - Electrical Engineering, EMI/EMC, RFI -  Introduction to EMI, EMC, RFI, Military EMC Standards, Radio Frequency Interference.

EMI Shielding RF Shielding - Tech-Etch designs and manufactures both standard catalog and customized shielding products.

Dealing with Computer generated RFI/EMI - Most of the time, the RFI generated is enough to render certain bands useless and on other bands, it may drown out any weak signals and distort or interfere with signals that you want.

TDK - Electronic Components & Materials - Electronic devices generate electromagnetic interferences, which can affect the proper functioning of electronic devices and systems

Here is one type i encountered in many T&M Instruments along with TDK too. It was Schaffner - electromagnetic compatibility - International leader in electromagnetic compatibility (EMC) and power quality (PQ). EMC Filters, RFI Suppression Chokes, Feedthrough Components.

Sunday, June 01, 2008

NO-NC SSR Plastic Box

This was a Fire Retardant Plastic Box which was made for the SSR I/O Stackable Modules. DC Control for an AC Load. Usually it is to control another Big Three phase contactor;

Pneumatic or Steam Valve, Solenoids-Motors. When Mounted at the end of the PCB it offers over 2kV Isolation from the Digital Circuits. The Output 230V signals NO-NC, can control Light Loads like the Coil of a Big 230V Relay also called contactor.

It could be Mounted on a PCB by soldering or a Plugin Base. It is better to have Crimped connections or Terminals. A very good quality spring Loaded Socket may also work but it has to be rated for many operations. Things like Nickle Alloy Plated, Beryllium Copper were the Materials Jargon. A contact resistance in the Terminals, a mismatch of alloys, electrochemical reactions, Corrosive Fumes, Brine or High Humidity can build a Loose connection into a Dangerous Sparking Contact.

Not only the Functionality of the SSR will be affected in a Sparking Contact, but a Risk of a Fire Developing. When Inflammable Materials or Volatile Liquids are Present Nearby, the risk is even greater.

Read More - Solid State Relays SSR

Temperature Controller 48-96

A 1/8 DIN Indicating Temperature Controller. This is a Analog Controller built around ICL7107. Read more here Temperature Measurement and Control.
48 96 Temperature Controller
This is a 48-96 DIN Temperature Controller, it is mains operated, it is in a Industrial Plastic Housing. It is not meant for very harsh environments. Suitable for Control Panels in Control Rooms. It has a accuracy and linearity of 0.5%. It had options of on-off or time proportional control

Saturday, May 03, 2008

Transistor Beta and Vce Tester

This was a Beta Hfe and Vce Measuring Instrument used in Incoming Inspection of Power Transistors made by me 16 years back.

Transistor Beta Tester

Custom Built Test Instruments

I designed and built many custom "engineered" Test Instruments. They were not prefect, as only one or two were fabricated. That means it will be costly to produce such instruments. It is just like tooling, you have to make some numbers to recover costs, or price it very high to compensate for the wastages and iterations.

Friday, May 02, 2008

Tera Ohm Meter and Insulation Tester

This is a 20 Tera Ohm Insulation Tester I made around 20 Years Back. It had even Polarization Index for Transformer Insulation. It generated 1000V DC Regulated Voltage and the pA leakage Current was Measured. See more here Insulation tester or Tera ohm meter.

Insulation Tester
A regulated, low ripple, high voltage of very low current capability is applied by instrument on a DUT (device under test). The leakage current in nA or pA (picoamps, nanoamps) is measured and readout, The Innovation i did was to measure the current in Vref and not Vin of ICL7107, this made the 1/x computation.

Also using the ICL7650 Chopper Stabilized amplifier must be done as shown in data sheets with grounded guard rings. pA will leak on the PCB itself if layout is not done keeping this in mind.

Wednesday, April 30, 2008

Historical Electricity Teaching Instruments

In February 1975, Deborah Jean Warner, a Curator of Physical Science at the National Museum of American History, called me to ask if Kenyon had any historical physics teaching apparatus. I looked around my office.......

Thomas B. Greenslade, Jr. - Professor Emeritus of Physics - Kenyon College, Gambier, Ohio

Historical Electricity Teaching Instruments

Electrical Measurements, Electric Motors, Electricity, Static Electricity.

Historical Electricity Teaching Instruments

Physics apparatus often goes by various names. The interrupter, the electrotome and the repeater are all the same instrument. Some apparatus has a person's name attached to it: Matteucci's apparatus or Wheatstone's bridge. Other apparatus isn't used any more: Packard's apparatus or the piezeometer.

LED brightness controler - Jaroslav Belza

LED brightness controler - Jaroslav Belza

White LED lantern powered from USB port. Jaroslav Belza

delabs Notes-

R1 Limits the LED current when T1 is fully Turned on or saturated. P1 forms a Variable Potential Divider, The Turning of P1 Pot gives a 0 - 5 V Variable Voltage Proportional to the turning, if it is a Linear Pot.(Audio Systems use a Log Pot as the Ear Hearing response to sound is Non-Linear.). As the impedance of this Voltage source is a bit high, it is from a 5K pot, it cannot be loaded with a low value resistor like 100E or 1K.

The R1 should limit the current to an optimum value in relation to LED Brightness vs. Battery Life. T1 chosen must have a Max Ic of at least Five times the LED current, for a long lasting product.

R2 you can figure out from the beta of the transistor. That you can learn at Transistor Operation - HyperPhysics.

Tuesday, April 22, 2008

VU Meter Circuits and Projects

Here is a collection of web pages of VU Meter projects that helps a newbie getting into the Electronics DIY Hobby Land.
VU Meter Circuits and Projects

A Hobby now in your School days or College can help you build a strong profession later. It is Edutainment that will make productive use of your spare time. Friends can do it as a group, during holidays. Parents should encourage healthy hobbies, as the children will grow in a positive and creative atmosphere.
Stereo Vu Meter Kit

This is a very eye appealing audio accessory. Displays an approximate output level for each channel of a stereo amplifier. Connects to the speaker terminal; levels are displayed in ten steps. User may select either a moving dot bar appearance. Uses two LM3915 IC's; includes a discussion of measuring audio power.

Saturday, April 19, 2008

The Scots Guide to Electronics

This course is designed to help you learn about components, circuits, and the use of electronics. You can explore the contents in whatever order you wish.The emphasis is on providing information starting at the 'absolute beginners' level, but we hope eventually to provide material of use to anyone interested in electronics and its applications ...

The Scots Guide to Electronics

This section of the Scots Guide deals with Analogue Electronics with a special emphasis on Audio-related topics. There are also some specialist pages on the properties of cables as these relate to audio.

The Scots Guide to Electronics

The First Eleven - Basic electronics courses sometimes make it appear as if electronic engineers have an obsession with voltmeters, batteries, and oscilloscopes. That's because it's often convenient to talk about these when presenting a course at a university, college, or wherever. In reality, the physics and electronics of practical systems like Hi-Fi's, TV's, computers, etc, are much more interesting.

The main components used in electronics are of two general types: passive (e.g. resistors and capacitors) and active (e.g. transistors and integrated circuits). The main difference between active and passive components is that active ones require to be powered in some way to make them work. Active components can also be used to amplify signals.

by J. C. G. Lesurf University of St Andrews Astronomy Group, Scotland.

Category Engineering - Wikibooks

This category contains a number of subcategories, books, and pages related to Electrical engineering. Books can be found on the Engineering EE. Courses can be found at Wikiversity:School of Engineering.

Subcategories include specific engineering disciplines, including Electrical Engineering, Computer Engineering, Mechanical Engineering, and Civil Engineering. Also, some books that are general to all disciplines are listed here.

Digital-to-analog converter

A DAC converts an abstract finite-precision number (usually a fixed-point binary number) into a physical quantity (e.g., a voltage or a pressure). In particular, DACs are often used to convert finite-precision time series data to a continually varying physical signal.

Digital-to-analog converter

Analog and Digital Conversion, Automatic Control Engineering, Automotive Systems. Basic Electrical Generation, Basic Electricity, Biography of Nikola Tesla.

Circuit Idea, Circuit Theory, Communication Systems, Control Systems. Digital Circuits, Digital Signal Processing, Electronics, Embedded Control Systems Design

Embedded Systems, Practical Electronics, Power Systems Analysis, Design, and Control Microprocessor Design, Engineering Tables, Semiconductors, SensorNetworks

Thursday, April 17, 2008

Science Toys - Edutainment at Home

Make toys at home with common household materials, often in only a few minutes, that demonstrate fascinating scientific principles. See also the Science Blog, - Creator - Simon Field

Science Toys - Edutainment at Home

This Website is a valuable resource for students to learn basics and get interested in electronics and computers - delabs

Science Toys - Edutainment at Home

Electromagnetism: - An electric motor in 10 minutes

The motor is simply a battery, a magnet, and a small coil of wire you make yourself. There is a secret to making it (which I will of course share with you) which is at the same time clever and delightfully simple.

Other Projects - Fun with High Voltage, A 10 minute railgun, A 30 second motor.
    Radio: A quick and simple radio

    The reason a crystal radio does not need any batteries is the amazing capabilities of the human ear. The ear is extremely sensitive to very faint sounds. The crystal radio uses only the energy of the radio waves sent by radio transmitters.

    Others are Building a radio in 10 minutes, Build a portable crystal radio, A radio out of household items, A simple AM transmitter, The Three-Penny Radio.
      Computers and Electronics: A Computer Controlled Transmitter

      In this project we will build a very simple radio transmitter that you attach to a serial port on your computer. The computer then runs a free program that converts words you type into radio signals that are decoded by another computer, using a cheap radio receiver, and a sound card.

      More - A Free Space Laser Data Transmitter, Fun With Solderless Breadboards, A Simple 1 Watt Amplifier

        Friday, April 11, 2008

        Electronics Club

        Electronics Club

        Example Projects, Construction of Projects, Soldering Guide, Study Electronics, Electronic Components, 555 Timer, Circuit Symbols.
        • Example Projects
        • Construction of Projects
        • Soldering Guide
        • Study Electronics
        • Electronic Components
        • Circuit Symbols
        John Hewes, Kelsey Park Sports College.

        (This is good place to start your electronics study, it has a practical and simple Approach - delabs)

        Product Design Precautions

        When you design a new Product or Engineer an existing one; communications and documentation is important. Creating a satisfying solution is the main thing. If requirements and specs or not properly developed it can lead to blame-games, wasted time and spoils the reputation.

        A firm also should do proper market study before the decision to design a product. Even a well designed product cannot be sold if it does not offer a cost-effective solution.

        Black Box Specifications

        Product Design Precautions
        • Start Projekt {
        • Customer Interaction and Communication to make a specs sheet and drawing.
        • Block Diagram, feasibility, cost, risk, samples demo and study similar ideas.
        • Effective designs are cost effective within customer budget, draft BOM costing.
        • Circuit and Code design and get more inputs from customer and then freeze specs.
        • Build Dummy for ergonomics and discuss, Prototype and start test at site or simulate.
        • Calibration and testing and production documentation drafts final costs.
        • Pilot Production of a small batch, rigorous test batch, and freeze production documents.
        • Documents and Prototypes to be given to Production Engineering.
        • Production Engineering continue engineering maintenance and quality issues.
        • } End Projekt

          GoTo Next Projekt
        (I had written this in Aug-05, it is my 90s experience, it may indicate some useful points - delabs)

        Monday, April 07, 2008

        Edison and his Inventions

        Thomas Alva Edison also known as "The Wizard of Menlo Park" was an American inventor and businessman, He is known for inventions like phonograph or gramophone, the motion picture camera and the electric light bulb.

        Thomas Alva Edison

        Edison and his Inventions - Inventing Entertainment: The Early Motion Pictures and Sound Recordings of the Edison Companies

        The Thomas A. Edison Papers - The Thomas A. Edison Papers Project, a research center at Rutgers School of Arts and Sciences, is one of the most ambitious editing projects ever undertaken by an American university.

        Edison - By the time he died in 1931, Thomas Edison was one of the most famous men in the world. The holder of more patents than any other inventor in history,

        The Phonograph - On December 7, 1877 Thomas Edison demonstrated his phonograph at the New York City offices of the nation's leading technical weekly publication, Scientific American. The following report set off a stampede of reporters to Edison's laboratory to hear the amazing device.

        Edison National Historic Site - Where Modern America Was Invented - Thomas Edison’s home and laboratory are a step back in time, when machines were run by belts and pulleys and music was played on phonographs.  Where to the passerby, the buildings betray little evidence of the industries they once started.  Discover where America’s greatest inventor changed our world forever.

        Miami Museum of Science - The Atoms Family

        This resource contains educational activities about energy concepts, the power of the sun, energy conservation, energy transformation, electricity and fossil fuels being presented by famous gothic horror characters.

        Miami Museum of Science - The Atoms Family

        Electrical Safety - Static Electricity - Fruity Electricity.

        Miami Museum of Science - The Atoms Family

        Flying a kite near any kind of overhead wires is VERY DANGEROUS! The overhead wires could shock the kite, the electricity would then travel down the kite's string and shock you!

        Atoms Family - Frankenstein Lightning Lab

        Only electrical plugs should be put into electrical outlets. Never place anything else into an electrical socket, it may shock you or start a fire!

        Lamps use electricity to make light and can get very hot! If things get to close to a hot lamp they can catch on fire!

        Hair dryers and water don't mix, and can be very dangerous! Never use a hair dryer near water and never place a hair dryer in water.

        Sunday, April 06, 2008

        Three Phase Solid State Relay

        This is R-Y-B three phase 40A 440V AC Solid State Relay with 3-30 V DC Control Signal. It has Built in HeatSink and Fan. It is good for Controlling a Bank of heaters. This model could go upto 120A with SSR's in parallel for Proportional Control.

        Solid State Relays SSR.

        This is a Contacter replacement, it will switch R-Y-B phases. It is a high power SSR. In some places
        it is unwise to use an SSR, a Electromechanical Contacter will perform better. The merit of SSR is fast switching, no wear and tear. No dust humidity influence.

        Three Phase SSR

        Saturday, April 05, 2008

        Tacho Counter for Speed and Quantity Measurement

        This was a Custom Built Product for Converting a 10-100 V Signal from a Motor Tacho to pulses, to indicate the distance moved by Conveyor belt with Job Material. The Digital Indicator would indicate the speed and the Mechanical Counter would Log Quantity of Materials Moved.

        Process Control Instrumentation

        Tacho Counter

        The voltage was first brought down to low levels with an attenuator and zener protection. A VCO and a monostable created a train of pulses. These pulses drive a darlington transistor pair which operates the Electromechanical Counter that has a Solenoid. The voltage is also scaled, calibrated and displayed on a Digital Voltmeter.

        The circuits are partially shown here, two versions.

        Voltage to Frequency Converter ICL8038

        In this the VCO chip is 8038, it is hard to procure, but it is an excellent chip.

        VCO - Voltage Controlled Oscillator using Opamps

        This is using opamps, hard to configure and build, but a proven design.

        The VCO can also be built by a Microcontroller chip which has an analog input. Any I/O port can be the Oscillator output. This is easily possible as this system is within the 1 MHz range.

        Analog Blind Dial On Delay Timer

        It is called analog dial timer as it has no digital display, but the chip is digital it is CD4541. It is Mains operated, you could make on-delay or off-delay. By changing the caps and resistors or with even dip-switches you could get timing of few seconds to many hours. Circuit is Analog Timer 4541 .

        Analog Blind Dial On Delay Timer

        Some timers energize the relay after a set delay on power start. Some start with relay energized and turn off after set time. Motors and big systems cannot take fast turn-on and turn-off, Some systems will require sections or modules to start one after another as they are interdependent. So Timers in automation were made to effect such delays, the early ones were mechanical clockwork.

        Analog Timer

        The CD4541BC Programmable Timer is designed with a 16-stage binary counter, an integrated oscillator for use with an external capacitor and two resistors, output control logic, and a special power-on reset circuit. The special features of the power-on reset circuit are first, no additional static power consumption and second, the part functions across the full voltage range (3V¨C15V) whether power-on reset is enabled or disabled.
        • Available division ratios 28, 210, 213, or 216.
        • Increments on positive edge clock transitions.
        • Built-in low power RC oscillator.
        • Oscillator frequency range . DC to 100 kHz.
        • Power on Auto reset initializes all counters.

        Saturday, March 29, 2008

        Digital Count-Up Timer Gadget

        Here is is Digital Timer Learning Gadget. The buttons make a sound and Light up internal LED lamps. Power On-Off control, Digital Timer; Start, Reset Scroll and Select are the controls. This will simulate the operation of a microcontroller based digital timer.

        Project Page programmable-digital-timer

        Press The Power on-off for a soft start, this is to prevent the inrush current from stressing the javascript components. Then it goes to a display test. The Start button can run or stop timer by toggling. The reset will Bring timer to 0000, format is min-sec.

        Set by pressing select to get a marker over orange digit, Use Scroll to set number. Press Start to start timer, Start to be off to set again. The buzzer will turn on when Time elapsed matches time set. and the alarm relay trips. And a Flashing Annunciator signals end of process. Now Reset will start process again and stop flashing LED.
        Digital Count-Up Timer Gadget

        To use this like a regular instrument, you need a small portable hand-held computer with browser. Fix that in a Cabinet by filing or grinding it to size and wire the relays and supply. :-)

        Thursday, March 27, 2008

        Learn Digital Logic Gates Operation

        The Gate is a digital component that is used to compute an output for certain inputs, the inputs and outputs have two states high-1 and low- 0. Let us assume high is 5V and low is 0V (like in CMOS). On a high level the LED will light up and on a low level the LED is off. Now let us see what Logic means.

        Screenshot of Widget

        Learn Digital Logic Gates Operation

        Digital Logic Gates
        Gates are what make many of ICs, the two popular families are the 40xx CMOS and the 74xx TTL . Now 40xx come in 74HCT40xx flavors which approach the quality of an ideal gate. Entire circuits with Gates can also be also be burnt into PLDs, FPGAs and CPLDs just like you burn your CDROM. Gates can also be implemented in assembly language which a microcontroller like 8051 will understand and execute.

        Hardware gate circuit will operate in real time, nano seconds delay will be there due to propagation delay, gate capacitance and FET switching times etc. Software or microcontroller gates code working will depend on both propagation delay and the CPU clock speed.

        digital-tutors - project page.

        Gates can be combined to make combinational or sequential logic circuits. combinational circuits are a complex network of gates interconnected to evaluate a pattern of output for patterns of input. Sequential circuits use memory elements hence output patterns depend both on input patterns and the memory of history of events. An example of combinational logic circuit is a seven segment display decoder CD4511 and and example for a sequential logic circuit is CD4029 up-down counter.

        The CD40xx CMOS family can work at even 3V-9V-12V DC and consume low power. The speed is not as fast as 74xx TTL family. It is good for simple portable battery powered circuits. The 74HCTxx series is good for low power and high speed but will work at 5V. When you have problems interfacing CMOS and TTL use 74HCTxx family.

        Tuesday, March 04, 2008

        Megger or Insulation Tester

        When a customer finds a Tera Ohm Meter expensive, Suggest a low cost scaled-down model to suit his need. These types are useful for people sub-contracting Telecom Equipment Manufacturing.

        Even if we have Developed a High Precision System we cannot sell it in a Market that needs an Affordable Instrument with lower Specs. Three Types of the same Product for Three levels of Affordability and Field of Application. Get the idea?

        Insulation Tester

        Test and Measurement Instruments

        This probably went upto 500V and 100V with a Toggle Switch and measured upto 1 Giga Ohm or 1000 Mega Ohms. The test voltage would be applied on the Switch, Connector or Magnetics to measure the leakage current in its insulation.

        The leakage current would be converted to voltage, clamped with diodes and fed to the Vref of a 7107 which displayed the Insulation Resistance by doing a 1/x. Normally we use Vin to measure the voltage, in this instrument the Vin holds the Reference.

        Monday, March 03, 2008

        Heater for Heating Chambers

        This was a Heater which was custom built for a CRT manufacturer, It is comprised of many Tubular finned heaters. And probably a big fan that worked at high temperatures. This was used in a Heating Chamber which aged or tested CRT monitors. It had a temperature controller, a remote indicator.

        CRT Chamber Heater

        Industrial Automation & Process Control

        Multi Zone Temperature Controller

        This is a Multi Zone Temperature Control panel used in Plastic Extrusion Moulding. We made many of these and it helped us learn cable management techniques. The panel is a standard way it was built and some of the merits were the selection of panel components and wiring expertise.

        Multi Zone Temperature Controller

        Monday, February 25, 2008

        Multizone Process Scanner

        This could take current or voltage inputs from many remote transmitters, 4-20mA or 0-1 V Inputs. Then it would display the calibrated value in a LED display. The Zone number was a digital display. This serves as a monitor of process values. It had a analog output with a digital channel byte-word output for interface with other instruments.

        This uses the CD4051-52 for the analog switching. Operating this at +/- 7.5V gives best isolation from channels and low ON resistance. Now you have many types of devices to do this.

        Multizone Scanner

        When a large area or object has to be heated, many heaters are used. This device can monitor and display the temperature at various points. The Operator then can make adjustments in heating or cooling so that he can maintain Uniform temperature or a Temperature Gradient as specified by the Process.

        There are many ways, these scanners are used. Many different parameters like pressure, temperature, level are measured with different sensors and converted to a 4-20 mA level using transmitters for each sensor. Then many parameters can be measured in one equipment, when it needs only periodic attention. As the scan rate can be set from 1 to 50 seconds, the operator will be able to keep a tab on the values or record it. This reduces the real estate required on the control panel. Then the control room can be small, as it has to be at a vantage point, with a birds view of the entire factory floor.

        Industrial Process Control Circuits

        Wednesday, January 30, 2008

        Sequential Timer - Pressure Switch

        This was built in a 96 X 96 Cabinet. It takes the process thru three timer delays and the pressure is measured after a certain stage and at a setpoint the process, job or DUT passes or Fails. It could be stress, strain or load testing on object.

        Sequential Timer

        User Manual - Sequential Timer - Pressure Switch

        Related Resources
        Simple Sequential Circuit -State Machine - This lab will implement a stopwatch mainly based on a finite state machine (FSM). Other parts contain display, timer, counter, etc...

        Synchronous switching of multiple electrical devices - An electronic timer consisting of CMOS integrated circuits is described that synchronously switches multiple electrical devices on and off..

        Tuesday, January 29, 2008

        SSR and Transmitter Enclosure

        This is the enclosure for the Encapsulated Mini RTD PT100 Transmitter and also Solid State Relays - SSR.SSR Enclosure

        Potted, Encapsulated in epoxy, hermetically sealed. It has a Nickel Plated Aluminum Plate insert molded. For removing heat from BTA41600.

        The plastic is a fire retardant high temperature grade. The epoxy is ciba araldite, fine alumina is filler. A transparent terminal cover for safety. It costed me an equivalent of 600-700 USD for tooling plastic parts.

        See also ...

        Three Phase Solid State Relay

        Monday, January 21, 2008

        Interfacing Microcontrollers

        At Beyond Logic and Embedded Processor Control you will find interesting information on interfacing.

        Real World variables are analog values, like the temperature of the Human Body. There may be Yes-No or digital events too, like the Water Level of a Tank or Door Close-Open. The former is measured by a Thermocouple and the Latter with a Proximity Switch.

        These values from the sensors have to be Quickly converted to a digital form and fed to the the uC by an interrupt or cyclic polling of ports. The "How Quickly" determines How "Real Time" you system response is.

        An analog value in instrumentation has to be at least 12 bit wide resolution, which is like 3-1/2, and the
        The ICL7135 4-1/2 gives +/- 20,000 counts at full scale, nearly 14bit wide data. This can be interfaced both in serial and parallel data links. The serial method is used when optical isolation is required from the sensor to control circuits. If the sensor is measuring the temperature of a Transformer, an optical isolation is absolutely required.

        delabs Technologies 06:48 20-Apr-07

        Embedded Process Control

        Microcontrollers are versatile for process control instrumentation, The Instruments need to be small and power efficient, they have to be immune to electrically noisy environments.

        When such a instrument is mounted closed to big machines, it has to be resistant to vibration failure due to harmonics. When it is used in ships or chemical industries, they need to be corrosion resistant. This makes Industrial Instruments a challenge to design, as the reliability is next only to Medical and Military instrumentation.

        In applications like data loggers, scanners and PID Controllers Microcontrollers are inevitable. The analog and digital counterparts that were built years back were difficult to maintain and very big in size. With a uC a 48*48 1/16 - DIN PID Box is possible, as shown here Newport Autotune PID.

        Modular Automation like PLC uses many uCs. There are Multiplexers, Analog and digital modules controlled by uC. Modern Computer based SCADA have wireless interfaces and transmitters using uC based intelligent circuits.

        delabs Technologies 06:48 20-Apr-07

        Friday, January 18, 2008

        80C31 and 8052 Microcontroller

        8052 Microcontroller :

        8048 and MCS-48 made designing with Microprocessors easy with built in I/O ports, RAM and Timer. The I/O ports for the 8085 was an external 8255. 8749 enabled users to burn and test firmware on an integrated UV Eprom.

        80C51-52 which came out as the fully evolved uC had built in Serial Ports UART and more Math, better Timer-Counter and Interrupt Handling. The 'C' is for CMOS that made handheld instruments possible due to low battery usage and lesser support chips.

        The Assembly Code MCS-51 set is used to program the chip. There is a 8052 Basic that can understand the Basic Language, useful for people who are not comfortable with mnemonics.

        Now we have 8051 chips with EE Flash and some have a watchdog and I2C too.

        delabs Technologies 06:48 20-Apr-07

        Microprocessors and Microcontrollers

        Analog devices like transistors and diodes lead to opamps and analog computing. This takes more parts but with fast devices can be real time. Then came Logic and Digital Circuits, here also big systems will take too many parts. A very Old hp Logic Analyzer instrument, could be HP1600A, had more than five large PCBs, Toggle Switches and numerous 74Fxx TTL Chips. I tried to revive it, it could not be fully restored.

        Then came the solution the Microprocessor.  Here the entire system goes into the firmware and a Hardware. Tool Set in the Microprocessor made up of Logic and Math, sequentially used to perform the same operation that would require innumerable Gates in a plain hardware digital circuit. But as it performs the operations one after another, it takes time, hence the speed is defined by the CPU Clock Speed and Bus width.

        When the External RAM and EPROM and other peripheral devices moved into the main package, MicroController were born. When more external devices merged with the MicroController. It formed a nearly complete computer, this is known as the SOC.
        delabs 06:48 20-Apr-07


        Basic Electronics
        Basics of Electronics
        Product Production
        Work Discipline
        Testing Points
        Learning Electronics
        Electronics Theory

        Production Notes
        Prototype Fabrication
        Electrical Circuits

        Scots Guide Electronics
        Engineering - Wikibooks
        Design Lab - Jim Svoboda
        DC Circuits UOG
        Socratic Electronics
        Blobz Guide Electric Circuits

        Product Design
        Product Development
        Constant Current Source
        Good Voltage Regulators
        Insulation Resistance
        Digital Insulation Tester
        DN Schematic PCB 04
        DN Product Design 07

        Hobby Circuits
        VU Meter Circuits
        LED brightness control
        555 Incredible Chip
        Process Control
        liquid level measurement
        Thermocouples and RTD
        Design ADC Interface uC
        Thermocouple Amplifier
        IA Instrumentation 02
        Temperature on DMM
        Optical Proximity Switch
        Analog Mux - Data Acquisition

        Test Measurement
        Instrumentation Automation
        NI Test and Measurement
        DMM Digital Multi Meter
        Oscilloscope in T&M
        IA Automation 01
        Build Instruments
        Tektronix T&M Equipment
        Educators Corner – Agilent

        Power Electronics
        UPS Background
        Transformer Connections
        DN Power Electronics 03
        DN Power Electronics 02
        Half Bridge Convertor SG3525

        Interfacing Microcontrollers
        Embedded Process Control
        80C31 8052 Microcontroller
        Microprocessors and uC
        Embedded Systems Design

        Good Voltage Regulators
        Relays and Contactors
        Potentiometers Trimpots
        Prototype Boards Types
        Types of Capacitors
        Types of Switches
        Resistors How they Work
        Coils Transformers SMPS
        Mains Transformers Types
        DN Components Selection 05

        Tutor Gadgets
        Count-Up Timer
        Digital Logic Gates
        Electronics Tutors

        Teaching Instruments
        Charles Proteus Steinmetz
        Muntzing a Circuit Design
        Teralab Electronics projects
        Historical Instruments

        Tables, Charts, Videos
        Binary and Hex
        Resistor Color Code
        Ohms Law
        Giga, Tera, Pico, Nano
        High Resistance Materials

        School - Analog Design
        DN Analog Basics 06
        DN Op-Amps 01
        TI Semiconductors