Tackling Graceful Shutdowns on the GBZ

[SidSilver]

OK I see.
I was just kidding

Have you tested it ?

[Felix]

OK I see.
I was just kidding

Have you tested it ?

No, I didn't because I don't have the powerboost nor the mosfets for it. This is all theoretically, but it should normally work.

[Camble]

OK I see.
I was just kidding
Have you tested it ?

No, I didn't because I don't have the powerboost nor the mosfets for it. This is all theoretically, but it should normally work.

Something like this?

[Camble]

Something like this?

Scratch that. I've spent a bit of time shopping around today and come up with what seems to be the best MOSFET to use.

These will turn on with 3v, have a max current draw of 1.1A, which should be more than enough for a Pi0, LCD, WiFi and Speaker. I worked out my max current usage at around 670mA.

https://www.rapidonline.com/fairchild-s ... et-47-0166

I'm going to order a few and try them out.

[Popcorn]

^ the price is right!

[SidSilver]

Someone managed to make it ?

@Popcorn : stupid question. When you trigger the reset button, the powerboost will power off right ?
But if it's off, can the pololu turn it on on switch on ?

[Fleder]

Someone managed to make it ?

@Popcorn : stupid question. When you trigger the reset button, the powerboost will power off right ?
But if it's off, can the pololu turn it on on switch on ?

I am not a 100% sure, but i think the powerboost will stay on. That is why some people here had concerns about it still draining a minimum for the LED for instance. But you could use a SPST Switch to cut off the power from battery to powerboost, if you want.

[SidSilver]

Someone managed to make it ?

@Popcorn : stupid question. When you trigger the reset button, the powerboost will power off right ?
But if it's off, can the pololu turn it on on switch on ?

I am not a 100% sure, but i think the powerboost will stay on. That is why some people here had concerns about it still draining a minimum for the LED for instance. But you could use a SPST Switch to cut off the power from battery to powerboost, if you want.

Yes, but Popcorn use a tact button as reset,
so what you mean is with the tact to Powerboost goes off during the button being pressed and on on release ?

[Fleder]

No, i was talking about another additional button, that physically cuts the connection between the battery and the powerboost.
That is a solution if you have concerns about it still being powered after shutting down.

[Camble]

I wasn't paying attention when looking at @Felix's diagram. Of course, the enhancement MOSFET doesn't need to have such a high current rating, as they are just acting as switches and the PowerBoost supplies the Pi without going through the MOSFET. The enhancement MOSFETs I ordered do the job just fine though.

Anyway, I was under the impression that the difference between enhancement and depletion was just the orientation of the MOSFET, which isn't the case. It's my understanding that an enhancement MOSFET is basically a normally open switch, while a depletion MOSFET is a normally closed switch. Depletion MOSFETs seem to be a little harder to source.

These are what I've settled on.

[Update] Don't use the depletion MOSFET detailed in this post. What you need is a P-channel JFET. 2N5460. See this page for more info.

More waiting, unfortunately, but what I have so far is looking good. The PowerBoost just won't shut off without a depletion MOSFET.

Oh, one more thing. The tech sheets for the two MOSFETs I chose:

ZVN4306A Enhancement MOSFET
DN2530 Depletion MOSFET Do not use!

Something else which may aid in searches. The packaging for these is TO-92.