Hi there.
I am starting debugging a circuit of mine, from last year. It features an Attiny804 controlling a couple of led strips and itself controlled either by buttons or a
voice recognition module.
Basically a switch (J7) turns on or off a mosfet which, in turn, connects the "GND" line of the recognition module. The switch status is sensed by the tiny which executes code to enable the mic or the buttons.
Everything works fine and dandy as long as my PSU is powering the circuit. But the friend I built this for uses powerbanks to power it and, while buttons work fine, it turns out that the VR module does not.
Furthermore I tried to see the changes in current by using my dmm6500 to capture whether this could be a problem BUT with the multimeter in-circuit, while it clicked through the ranges, the VR module started working even powered from the PB.
To measure current I then tried and put a 1R resistor (with breakout cables and a breadboard) and connected my dmm in parallel to measure voltages (I thought the DMM was messing something up) and 1R was enough in series to make it work fine, it seemed. I tried then, experimenting, with a 0R1 and it stopped working again. I was able to measure (I don't remember in which way) around 180mA of peak startup current.
I then put everything back as it was (ie: no resistances, PB not working, PSU working), but I had been clumsy and accidentally disconnected the VCC cable from the VR module and… even with the powerbank everything was working!! I assume power trickled down from the TX-RX lines, but I don't get how or why I have this behaviour. I really want to learn something here.
Can you please give me any pointers? At this point I'm scared of VR modules.
Cheers
PS: I attached the schematic, sorry if it's partly Italian, everything should be there tho