9v battery

Can I wire a 9v harness inline to the power switch and have the Shruti-1 operate on or off the brick with out blowing up the battery or needing to unhook it every time I plug in the power? Do I need to add another component to bypass the battery when plugging it in?

Will the battery get sapped like a guitar pedal if I leave it plugged in?

Thanks for any advise.

you could use a DPDT switch that switches both + and - to either psu or battery. (DT for an off position)

What about replacing the main power switch by a SP3T (SPTT) switch. The common pin is soldered at the pad at the bottom, near the LM7805. One of the 3 “throw” pins is soldered at the pad at the top, near the DC jack. The other one is left unconnected. The last one is connected to the battery +. The battery - is connected to one of the points at GND.

This way you have 3 positions on the switch: Off, battery and DC jack.

Thanks guys.

Speaking of GND as one of the points on the board I’m guessing your referring to the GND point on the HackMe Header? Are there more than one point there?
Or speaking of the GND on the switch?

You can have a look at the board image. In addition to the GND connector on HACK_ME, there are many other points on the board at ground potential where you could solder the - of the battery clip ; eg the middle pad of the LM7805

Gottcha :wink:

If I understood well, the scheme should be the following:


But, Olivier, there are two things I don’t understand:

  • you write of 4 pins of the SP3T (the common + 3 “throw”, with one left unconnected) but in my search I found only SP3T with 3 pins. In fact my scheme is considering a 3 pins, on-off-on SP3T button. Am I missing something?
  • when you say it’s possible to connect the (-) pole of the battery to the ground pad of the LM7805, you mean that I can solder the wire on the already soldered centre leg of the 7805? Or, more precisely, can I solder both wire andLM7805 leg to the same pad?
  • You can use either a 3 positions/4 pins switch (on-on-on, in this case you need to leave one of the “on” unconnected), or a 3 positions/3 pins switch (on-off-on).
  • It doesn’t matter. Just make sure that the - of the battery is electrically connected to a point of the PCB at ground potential. There are many of them!