Now that everything is working, I want to have a ready-to use printed circuit board for it. Came up with this:
It’s tiny – about 48 x 12 mm – even though it’s based entirely on through-hole parts. The idea is to build it up, add wires, and then encapsulate the whole thing in heat-shrink tubing to reduce the number of contact points.
It can not be repeated enough: when tied to AC mains, the ENTIRE circuit carries AC mains voltage levels!
I have a couple of configurations in mind (see yesterday’s post for the schematic):
- with C1 a 10 nF X2 cap and C4 replaced by a wire, this delivers an average of 0.3 mA on 230 VAC mains
- with C1 a 22 nF X2 cap and C4 replaced by a wire, this delivers an average of 0.3 mA on 115 VAC mains
- with both C1 and C4 22 nF caps, this supplies 0.3 mA on 230 VAC with no direct connection to AC mains
- with C1 and C4 replaced by a wire, this supply can be used with 10..24V DC in – which is great for testing
- with C1 and C4 each replaced by a 220 kΩ resistor, and R1 by a 1N4007 diode, this becomes a somewhat less efficient (but lower-profile) resistive version, again delivering up to 0.3 mA at 230 VAC
With C4 replaced by a wire, this circuit will have its “GND” output tied directly to the “N” input. This is important when powering the AC current monitor, which needs to have one side of its shunt at 0V relative to AC mains.
Note that no matter what, even with C1 and C4 both included, faults can develop in this circuit which cause the “low voltage” output of the circuit to end up directly tied to an AC mains “live” line. This is not, and will never be, a “safe” circuit. It can only be used safely while enclosed in a plastic box, with no contacts or parts sticking out.
In all cases, the on-board regulator will be activated once the input voltage rises to about 6V. This is the key to being able to power up a JeeNode or JeeNode Micro with their on-board RFM12B module.