October 2007

• Power mosfets, transistors or IGBT’s should be electrically isolated very well from heatsink with alumina, mica or silpad. It could withstand 2KV -5KV DC, related to product safety. Also these heatsinks should not be earthed but floating, do not fix to the metal chassis for maximum safety.
• Whenever you use nuts and bolts to fasten a PCB or parts to a cabinet use a spring washer, double nut or adhesive to prevent slip. When a loose nut falls on the pcb or transformer sparks will fly.
• Quality: cost effective design, quality components, quality workmanship with good testing can result in a quality product. The packaging and production engineering too is important.
• Earthing is important, ensure it’s perfect, the neutral to earth could be 5V AC max., also a circuit breaker and fuse a must. Use a electrical earth leakage circuit breaker to protect both man and machine.
• A freewheeling diode should be used across a relay, solenoid coil or motor because inductive kickback will damage transistor or mosfet. High current loads like relays can reset logic circuits if ground is not connected well, It also produces more ripple in supply, so it is better to have a separate supply for such parts.
• Extra care should be taken to prevent injury to eyes while working. Also 230V/110V shock can be fatal. working on high energy electrical circuits and power electronics should be with all precautions.
• The most common reason of DMM failure is when a person tries to measure 230V AC with a DMM in current or ohms mode, with the probes in the wrong sockets. Use external attenuators and shunts.
• Unix lead to all the operating systems (OS) today here is the history, UNIX history with photos of the gurus.
• This invention lead to modern electronics, computers and internet look at this page, Transistor Photo.

What is Hands-On Electronics ?

Radio-Electronics (Gernsback Publications Inc.) started a quarterly Special Projects magazine in 1980. After 10 issues it was renamed Hands-On Electronics in the summer of 1984.

“More than 600 pages of assembly instructions, schematics, program listings, catalogs, photos and much, much more!” swtpc

(I used to read the Radio Electronics in The Indian Institute of World Culture which has a unique magazine section with magazines from all over the world - ananth)

• Snubbers consisting of R-C should be used across switches, relay contacts, MOSFETS when switching inductive loads, this will absorb the spike and save the device.
• Use RTV (room temperature vulcanizing) silicone rubber compound or Varnish on PCB-devices to avoid corrosion-dust. more so in industrial environment, ships and chemical industries.
• Transformers used in SMPS could be split bobbin for product safety, and transformers should be resin impregnated, a human life cannot be lost by using a badly made product.
• Ceramic capacitors leak a bit, electrolytics leak a lot but plastic or mica capacitors do not leak at all, near perfect. An oscillator with a RC time setting needs a plastic cap for stability.
• 12V lead acid batteries should be charged with a constant current CC and constant voltage charger the CV being 13.6V. Deep discharge and over charging will reduce the cycles.
• Lead acid batteries need a monthly distilled water update to ensure long life, sealed lead acid dont need attention. Keep lead acid batteries in well ventilated area due to acid fumes.
• In a SMPS which is not earthed the floating (unconnected) earth terminal will give a slight shock due to the two Y caps connected to earth from phase and neutral.
• Electric Shock can kill hence take great care, Electrolytic capacitors burst and Transformers catch fire. turn off equipment after use. turn off all electricity when going out of town.
• In industrial electronics equipment, connectors are a source of many problems, hence avoid connectors. vibrations, corrosion and frequent usage will result in strange problems.
• A DMM in diode mode or resistance mode can be used to test IR diodes, take it under 100W lamp and measure, cover the IR diode and measure you will see a response in proper polarity.
• Alumina-Aluminum oxide powder mixed in epoxy resin (araldite) can make thermally conductive insulating filler, heatsinks. The Alumina must be free of moisture and very dry.
• Inductive kickback starts a tubelight or automobile as high voltages are produced when current in inductor is turned off. This also is the cause of failure in power semiconductors.