Learning Electronics by Experimenting

How To Learn Electronics :

Theory must be studied once and referred again and again as you do practicals. One is by building DIY projects and then modifying them. Also Repair of equipment, troubleshooting, testing and calibrating. Then you know how components behave and real life limitations. Now design and engineer a product and test it at customer site. do a pilot production and test with more clients. Now you will learn to think based on practical application.

• Do not mix mechanical and electrical connections, these leads to failures and frequent need of repairs and service.
• 80C51 ports can sink more current but source very less, hence use a 10k pull up at all the ports or outputs.
• When using a double or multi layer pcb make one layer a ground plane, all decoupling caps ground linked to it.
• RF or near RF multilayer PCB have 2 layers as ground plane and tracks in the layer in between, faraday cage.
• High voltage or current stress, mechanical vibration, user misuse, High Energy stress (freq and voltage), aging (cycles) cause failure.
• Before you open a PC remove power, telephone modem and LAN cables else finger and screwdriver in wrong place can zap chips.
• The Contact resistance of connectors, thermocouple effects in connectors and solder joints and thermal gradients over the PCB can cause errors when you measure in high resolution.
• When we draw circuits we have to keep in mind the readability, the circuit should be laid out according to the signal flow, the input output ports shown in the periphery of circuit.
• Firmware must be developed in increments, tested in increments, backed up in increments, must be modular (include) reuse.
• When you are soldering or cutting leads, room should have cross ventilation, protective glasses for eyes and a good stand.
• Good earthing, servo motor regulated mains supply, earth leakage circuit breaker and over current circuit breaker, HRC fuse are some safety steps to take.
• When working with HV or HE circuits wear shoes, keep yourself dry, the supply board should have above protections in red.
• Small signal diode 1N4148 switches at 4nS, current of 70mA and 70V withstand capacity.
• 2N2222 and 2N2907 form a fast switching NPN-PNP pair and have been around for decades.
  

More Design Notes 2005

The high voltage side must have layer to layer (mylar) insulation, means wind a layer and then put the yellow mylar tape, make tape concave so no strands should slip over to next layer, use split bobbin if possible. have terminations far away and enclosed for safety. vacuum impregnate with natural resin or epoxy depending on voltage and environment. product safety is very important.

In my circuits you might have seen i use HDSP-5501 common anode and HDSP-5503 common cathode available at digi-key, liteon LTS series like LTS543 may be same, at mouser i found out that MAN6980 of fairchild may also do.

Tristate output, High Impedance and Floating all mean the same when it comes to IC Inputs-Outputs. It means the pin is insulated from rest of circuit in the IC. That means it will not influence the node or bus it is connected to. A DMM terminals are floating means that the hand held plastic DMM has no electrical conductive link to earth or ground.

EMI-RFI causes-Switching Loads Simultaneously (inductive loads). Power factor correction capacitors and devices. Lightning strikes (enhanced by earth faults). Line Inductance (inductive kickback, resonance). DC and AC Drives for Motors. Rectifiers with large filters and stray inductance.

You can use hyper terminal to upload code to single board computers 80C51 like in BINARY or ASCII. Hyper Terminal Website. It is available in all windows default installations.

98spct38.pdf circuit in delabs analog circuits has some changes, use LF356 or TLO71 in place of CA3140 as it may be obsolete, the bias should be in pA, any FET input opamp is fine. The caps for sample hold are 10uF tantalum but for long hold times use 1uF plastic multilayer and clean-IPA + coat PCB with epoxy. 8 channel analog mux with sample hold, analog, pdf.

Design as per inventory : when you design a new product, we can design it with new types of parts, but it is also important to use parts that are standard to the company's inventory, Also you need to use up the parts which have been accumulated due to a discontinued product line or a failed idea. This way the design becomes more frugal and efficient. It also saves the company to build a new part type stock.

Engineering and Product Design Management

• ASICs are for only very big companies, or for products which have a long product life cycle. for a small company in consumer electronics it is not good, because by the time you get the ASIC out the product model is obsolete.
• For low volume production use FPGA or CPLD, or even flash based microcontrollers, so that all your inventory can be reused and recycled, only change the software. but for say cell phones or a LAN card ASIC is fine. Volumes are good in cell phones and for lan cards the technology is matured.
• Whatever the method keep design flexible and modular for reuse and to save cost. remember the hardware is difficult to alter, software can be altered even at customer site, flash has made this possible
• In the future chips will be both analog and digital programmable with flash, and all the stores will have is blank chips. do not end up with too much inventory which is not good for the environment and is useful in only land fills.
• Some FPGA, CPLD, ASIC links, WinCUPL, Design and Reuse, fpga4fun.

• If a product gives three years life with minimum service support it can save itself from building a bad reputation. six years will establish the brand on a long term basis, twelve years of product life you will have the user of the product selling for you. if you want to improve sales by giving a new model every three years, you will need a lot of innovation on the product and you need to buy back the old ones for a big discount, you can bear some cost for brand loyalty and hence build a reputation for more sales in the future. This implies proper and sensible investments in product design and development, engineering, reliability, standards and quality will help a company survive long term.

If Inputs are Distorted, The Outputs are Noisy.
Even if the Amplifier is Very Good.

If Raw Materials are of Poor Quality, The Finished Goods are Defective.
Even if the Process and Machinery is State Of The Art.

If the Specifications are incomplete, The Prototype will be rejected.
Even if the Design and Tools are Perfect.

Solderman - 1707 AD

Enginnering and Servicing Notes

• This circuit of delabs has mistakes. 4A charger PWM, pdf in Power Electronic Circuits U2C must be a buffer not an inverter or swap pins 10 and 9 of U1C then only it will oscillate. Circuit File Name ST10_1.pdf .
• This circuit of delabs has mistakes. Errata-2, +5/-5 dual supply from 12V DC, pdf Power Electronic Circuits 7905 regulator Input and Output lines to be swapped. use 79L05 for low current. Circuit File Name dact0017.pdf.
• A Temperature Controller was fixed in a PCB manufacturer's Works, The readings was fluctuating and soon stopped working properly, the service engineer went and found that there was a strong smell of ammonia around the unit. When opened the tracks were eaten away by rapid corrosion and some of the component leads had disappeared. So another controller was made with extra coats of lacquer-varnish all over and RTV compound in many places. That solved the problem.
• In above real life example, If production quantities were required then you need to vacuum impregnate modules in epoxy resin. These reworks or fixes will add rapidly to the BOM bill of Materials Cost. Then cost of fixing. So customers are of five types home-user, industrial, hazardous, military and medical. So Components are to be selected and product engineered and costed accordingly in that order.
• If you put the DMM in 2V mode and measure the voltage across a ordinary LED near a 40W lamp you will see around 200mV. Turn off 40W lamp the mV will fall near 0. Even metal-can transistors with their top ground away will become photo sensors.
• When you measure low voltages or high resistance like 1M with a DMM your body must not be in contact with the probe tips. Body resistance is low in comparison so error in reading or loading of mV from sensor, in sensitive and high impedance ranges.