Isolation Transformer for Safety

Sometimes we just build a circuit that uses battery power supply. This is true when we deal like microcontroller circuit or kits, but sometimes we need to deal with high voltage circuitry likes AC lamp dimmer, flyback, power supply circuit. Actually, DC circuit is more dangerous than AC circuit, and what item that we needed for our safety? Of course Isolation Transformer, please don’t miss this as you are electronic enthusiast, especially when you are probing with your oscilloscope probes. You have a chance to damage your oscilloscope if you don’t use an isolation transformer. No matter you are repairer, home brewer, or just a hobbyist like to building kits. 

We can make simple deductions from it’s name “isolation”. Yes, this thing makes us isolated from the mains supply so we could protect when touch something wrong on our circuit. One note to remember, this Isolation transformer didn’t protect us when we touch two sources from mains supply like as Live and Neutral together. We just protected if we touch one of the source from mains supply. Yes, I said one of the source from mains supply. Why? Usually when we touch Live line in power supply and our feet still on earth / ground we could get an electrocuted because our body makes direct connection to Neutral line. You can get a deep explained about this at allaboutcircuits.com lesson books first chapter about safety precautions.

As repairer, sometimes I need to do voltage testing to fasten my job. I can’t avoid this because voltage testing method really saves time and useful. You can see from below picture if you have a spare transformer on your bench and want to build it yourself. You just need two transformers which have same voltage rating on it’s secondary. 

Please don’t connect mains ground with transformer output ground TRAN2, it needs to isolated from you. Two transformers which I name TRAN1 and TRAN2 could be any transformer, but if you concern about electronic equipments wattage which could be powered from this isolation transformer, you have to use big enough VA rating for the transformer. CMIIW, I think 100VA more than enough for home consumer equipments like a TV, radio, monitor and etc. Enthusiast about this electronic thing make me think safety first when do repair or other electronics job because it would kill me if I care less. Thank you for coming here.