Onoff shim with IQAudio DigiAmp+?


#1

First time poster, but I’m hoping someone will have the answer!

I’m looking for an elegant on/off power switch for my Rpi3 with the IQAudio DigiAmp+ mounted on the pi, which has a perma-proto board inbetween.

Is it possible to use the OnOff shim in a breakout capacity? The Amp doesn’t have header pins mounted on top so I can’t place it on top.

If I can attach it to the perma proto, how would I run power through to it?

ETA: Perma-proto is used for wiring up an LCD and physical buttons thus far


#2

The pinout for the on off shim is here, https://pinout.xyz/pinout/onoff_shim#
Mounting it to the Perma Proto with a male header could prove a bit tricky. One way to do it is to use a single row male header for the +5V, +5V, Ground etc row. The 6 pins on the outside edge. Solder the header on that row, then solder it to the Perma Proto and trim off the excess with wire cutters. Then use jumper wire to hook those pins up to the matching pads for those pins on the GPIO. Then just use two jumper wires for the BCM 4 and BCM 17. Only don’t use a header. Just solder one end right to the on off shim, and the other end on the matching pad on the Perma Proto for that GPIO pin. Then just feed your power in via the on off shim. Keep in mind you need access to its Micro USB port when you place it on the perma proto.

I use Perma Proto’s a lot. They are great for adding a RTC of headers for sensors and breakout boards.


#3

Thanks for the reply, that all makes sense for future projects.

I forgot to mention in my post that the amp runs off an external 19v supply
which in turn powers the pi, but I’ve no idea how it does so, I assume
through the pins it uses

This being the case, do you think I would be able to attach the shim to
perma proto as you suggested, but miss out the part where I plug in the
power?

This is the one part I can’t get my head around right now!


#4

If the On Off shim can be back powered via the GPIO 5V and GRD pins it should work? It should do the shut down part anyway. Not sure it will boot the Pi back up though?

And alternative to the on off shim would be to wire a switch to a GPIO pin and have it shut down the Pi. All you need is a normally open momentary switch, an arcade button will work, and some python code. I’ve done it in the past. I don’t know if I saved my code though.
Boot up can be done by wiring a push button switch to the RUN terminals. They should be handy to the GPIO header. Same type of switch as above. I do this on my KODI Pi. I do a shutdown but don’t unplug my power supply. When i want to use it again I press the button and the Pi boots up. Just don’t press it while its running. It will do a forced reboot.


#5

Yeah, that had been my original plan, but I cannot get the switches to work
the way I need them to. I want to have one toggle switch, and I can get the
toggle to shutdown, but getting it to boot back up is a problem but I’m
hoping it can be resolved with the toggle switches I’ve now found (first
time I’ve wired toggle switches) as connecting the RUN pins doesn’t do
anything but halt it, but I think the momentary toggle I have isn’t
actually momentary so it’s holding the RUN pins closed rather than opening
them back up, as it will release as soon as I toggle out of the state.

I was hoping to find something as an alternative solution without wiring up
a circuit myself, as the power plug will always be an issue (and my
knowledge of components doesn’t stretch far enough right now to come up
with a solution).

I should have the new toggles next week to try out.

Thanks for your help on this!


#6

Yeah, you don’t want toggle switches that latch, stay switched when you release them. You want ones where they return to the off state as soon as you take your finger off of them. Like the button for a door bell. I used push buttons, not toggle switches. Just personal choice. A continuous short on the run pins will just hold the CPU in a reset state. Look for “momentary contact” in the description of the switch. You also want “normally open” if its only a two contact switch. Most toggle switches will have three terminals. A normally open, common, and normally closed. You want to use the normally open and common for the RUN switch. On my pirate radio I used arcade buttons.
https://shop.pimoroni.com/products/mini-arcade-buttons


#7

Thanks for that, that really helps in clarifying what I’ll need. I’ve found
some that appear to spring back when released so I’ll try them.

I’ll also order a button at the same time as this is starting to really
annoy me! I’m sure I’ll find a use for all the other toggles I’ve tried at
some point!