Is anyone using a transformerless power supply? I was wondering because of the short sharp power draw during wifi transmits. Large caps would mitigate the power spikes.
You mean a switch mode power supply? I have been using that, didn’t have any problems.
For low power draw it’s possible to use a transformerless design, no windings just a few discrete components and it’s mains voltage to low voltage much cheaper than a transformer but it needs to be sized to suit the load. I was just wondering if anyone had done it already.
I investigated it a little bit when I was doing my watt meter project. Bottom line is that I had two problems - 1) I don’t have enough skill to do it well. 2) it seems the power level from such a circuit is pretty low or at least the efficiency is low.
These designs are not isolated so they are not suitable for many things but for a closed-case power meter it did seem a possibility.
I ended up using a Recom module.
A hijacked transformer-less power supply (they are everywhere) couldn’t provide the startup current for an imp. That’s not to say a larger supply or bigger caps wouldn’t work.
Tested @240v, 50Hz, 0.474uF mains cap, 100ohm series resistor, 5.1v zener.
Mjkuwp94’s suggestion of a Recom module is looking good even with the higher price tag.
I’ve used these to power Aprils boards http://uk.farnell.com/myrra/47122/power-supply-2-75w-5vdc/dp/1825773