Posts: 1
Joined: Sat Aug 31, 2019 3:32 pm

Car clutch sensor

Sat Aug 31, 2019 3:45 pm

I'm doing some research for a project for my brother's ute to make a sensor to warn him when he's riding the clutch. Now the clutch pedal has a sensor switch for the cruise control, so I want to tap off that, but I have no experience working with 12V circuits, especially together with a 5V controller. Due to other requirements of the project it seems that an RPi Zero W would be a fair choice, but I don't know what to do so that the switch won't fry the Pi. I get the idea that I need a relay or a buck converter or something, but I've seen some conflicting or unhelpful answers in my searches. What do I need to put in between the switch and the Pi to get a signal for when the switch is closed?

Posts: 8561
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: Car clutch sensor

Sun Sep 01, 2019 3:05 pm

How you would wire anything in to the existing switch would depend on how that itself is wired in. It might be a traditional short to chassis / 0V but could easily be something else these days.

Have you checked that switch activates when he's riding the clutch ?

Have you checked with his insurance company how tapping into a safety critical function will affect his insurance ? Especially if he is involved in an accident, and, heaven forbid, a fatal one.

In fact, have you done a comprehensive risk analysis of what may go wrong ? Particularly with respect to innocent parties.

Personally I would recommend against doing what you are proposing.

Posts: 445
Joined: Mon Mar 19, 2018 1:18 pm

Re: Car clutch sensor

Sun Sep 01, 2019 10:55 pm

For each gear there-s a fixed ratio between road speed and engine RPM. Anything not closely matching any one of these ratios can be attributed to clutch not being fully engaged.

I think (not entirely sure) that both road speed (odometer) and engine rpm are readable with an OBD bluetooth adapter.

That would help you not to wire the car in ways it wasn't meant to be wired.

Posts: 188
Joined: Fri Jul 06, 2018 2:13 am
Location: USA

Re: Car clutch sensor

Tue Sep 03, 2019 3:18 am

Other than tapping off an existing switch (such as the one tied to the cruise control), you could add your own switch to the clutch pedal. Where the switch resides would depend on how the clutch is set up. The switch could either reside under the dash by the pedal, or if there is a lever somewhere (like my truck - lever near the transmission), it could be located there (with sufficient road grime isolation of course)....
I wouldn't recommend connecting anything to the cruise control switch because (as was already mentioned), doing so could cause unwanted operation. Worst case being that the cruise no longer shuts off when the clutch is depressed.

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