A couple of years ago I ordered a Soft Power Switch for a hobby project. Unfortunately that project got delayed and I only got to looking at the SPS I ordered recently. I noticed that one of the components was missing (manufacturing error, I guess). With the help of the schematic and a multimeter I found it was D2 that was left off, the 3.3V clamp zener on the sense/control pin.
However, in my circuit the output of the SPS goes to an ATtiny85V which can handle the 3.7 volts from the battery (in fact it’s powered directly from the SYS voltage output so it’s VCC is higher than 3.3V).
Is D2 only serving the purpose of a clamping diode for 3.3V-only systems and the SPS should work without it, or should I find a 3.3V Zener and replace it? I can’t order a new SPS because it’s retired.
Is the switch functioning the way it should?
Haven’t been able to test it yet. But, considering that all the other components are present, it might. I just don’t want to have it not work and then not know whether it’s because of the zener diode or because of the MOSFET threshold voltage issue mentioned by Member #1860235 on the reviews at the bottom of the product page.
Update: I just tested the circuit with a small 110mAh lipo battery.
- When I plug in the battery initially the LED is on, despite the fact that the jumper on the bottom to set the initial power-up state is set to the default of "off".
- I hold the button for 30 seconds and let go, and the LED turns off when I let go *and then turns on again after about 7 seconds*.
- I am pressing the button with a plastic screwdriver and the whole thing is sitting on a wooden table so nothing could possibly be shorting unless there is a flaw in the board.
- There is nothing else connected to the SPS except for the battery.
Could the lack of a zener diode be causing the SPS to automatically turn back on because the voltage at the sense/control pin is too high?
