Vlakh
Posts: 3
Joined: Sat Sep 05, 2020 3:04 pm

Re: Automatic shutdown for pi in a car

Sun Sep 06, 2020 5:25 am

I guess I should put the capacitor after the optical sensor so it can turn off but still give some power to the relay coil.

RonR
Posts: 2515
Joined: Tue Apr 12, 2016 10:29 pm
Location: US

Re: Automatic shutdown for pi in a car

Sun Sep 06, 2020 7:28 pm

Vlakh wrote:
Sun Sep 06, 2020 5:25 am
I guess I should put the capacitor after the optical sensor so it can turn off but still give some power to the relay coil.

It doesn't matter where you put the capacitor in a series circuit like you have -- the relay and opto-isolator are only going to see a short pulse and not stay active when the 12V Ignition is applied..

drgeoff
Posts: 12394
Joined: Wed Jan 25, 2012 6:39 pm

Re: Automatic shutdown for pi in a car

Sun Sep 06, 2020 7:43 pm

RonR wrote:
Sun Sep 06, 2020 7:28 pm
Vlakh wrote:
Sun Sep 06, 2020 5:25 am
I guess I should put thee capacitor after the optical sensor so it can turn off but still give some power to the relay coil.

It doesn't matter where you put the capacitor in a series circuit like you have -- the relay and opto-isolator are only going to see a short pulse and not stay active when the 12V Ignition is applied..
It doesn't matter where you put the capacitor in that series circuit because it won't work. :(

There is no path to supply a steady current to keep the relay energised.
Quis custodiet ipsos custodes?

Vlakh
Posts: 3
Joined: Sat Sep 05, 2020 3:04 pm

Re: Automatic shutdown for pi in a car

Mon Sep 07, 2020 5:54 am

Thanks for reply guys,
Here is a slightly modified version.
Do you guys think it might work?
Attachments
cc2.png
cc2.png (34.41 KiB) Viewed 407 times

tg00
Posts: 1
Joined: Thu Sep 10, 2020 11:58 pm

Re: Automatic shutdown for pi in a car

Fri Sep 11, 2020 2:18 am

You should check out these videos, this person has done exactly what you're looking to do:

https://www.youtube.com/watch?v=OGFAo9j1vSc
https://www.youtube.com/watch?v=DPwnaYJWL5g

Here's a screenshot of the diagram they presented in the first video, but unfortunately it's very high level and doesn't indicate grounds/positions of the wires. - https://imgur.com/DBe5nEY

I'm planning to recreate this setup but am not well versed in creating circuits like this. Is anyone able to create a more detailed wiring diagram or schematic based off of what this person had done?

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