Here, I will gather anecdotes, tips and tricks that I have heard and that I don’t want to forget about.
- A good high wattage load resistor can be created using a bucket of salt water with two electrodes. The impedance can be adjusted by adding salt.
- If there is a short somewhere on a PCB with non-coated tracks, a good method for tracing the path of the short is to put a voltage from a lab power supply with current limiting over the short, limited at a suitably low current. With a multimeter, the current can then be traced using millivolt measurements. Any PCB track where the voltage is rapidly changing has a substantial current flowing through it. Whenever there is a junction with several tracks, this method can be used to locate the path that the short circuit current is traveling through.
- When troubleshooting some circuits powered from the mains grid, a cheap and simple way of protecting your circuit while experiment, is to use a 40W/60W light bulb as a short circuit indicator and current limiter, by putting it in series with the mains input. If it only barely lights up, the circuit has a higher impedance than the bulb, but if the bulb is fully lighted, that means there is a short in the circuit.
- A transistor
junction voltage will decrease by about 2 mV/°C and increase by about 60 mV per decade of collector current.
Things to remember for PCB layouts:
- For designs that are to be powered from USB or similar sources, be sure to still include a header connected to the supply rails so that early debugging can be done using a lab supply.