Yesterday’s post described a new test setup to be able to safely experiment with low- to medium-range AC voltages. As a first check when working on new AC mains powered circuits, and to allow me to poke around.
The main idea is to use a few small transformers to create relatively weak AC power sources with a range of different voltage outputs. Here’s one way to connect their six secondary windings together:
The key safety feature is the connection to ground. Anchoring the middle of the output signal to ground effectively halves the voltage when you touch one of the outputs. It also (sort of) centers the sine wave around earth ground.
Note that touching both ends of the 6 series-connected secondaries will still cause a scary 148 VAC jolt.
To make this more convenient to test with, a double-pole 11-position rotary switch will be used (the best I could find for a reasonable price). This will allow me to switch between each of the above voltages, as well as 0V.
Every position up to 92V will have at most 56V to ground, the highest two positions will make that 74V and 84V, respectively (through secondary coils designed to supply at most 20 mA). I’ll consider up to 46V to be safe.
Here are the parts I got from DigiKey – and how I would like to arrange it all:
Next step is to come up with a nice box for it – the work never ends!