I have an accessory on my truck that gets power when the key is in the On position. I would like to have this accessory lose power when the truck starts to move. I thought that I might be able to tap into the VSS (Vehicle Speed Sensor) and detect some sort of voltage when the truck starts to move and this would be the signal to cut power to this accessory.

I am just learning about electronics so I am a novice at best, not sure if this this even possible. Would anyone know if I could set this up and what I would need to do it?

Thanks.

 

I'd be leary of tying into any sensor to control anything it wasn't designed for. Kinda sketchy on your intentions, but a simple on/off switch would be better. But I'm sure you have your reasons.

 

You would have to build a complex electronic circuit, that would read the vss signal, convert it to a variable voltage, and then set the threshold to a transistor switch which then could activate a relay. All very complex with a lot of design work involved. Whatever you tie into the VSS has to be a very "lightweight" circuit (technical term would be "high impedance") so it can sample the signal, but not load it down and kill it for all the other devices that use it(speedo/cluster, tranny/engine computer, ABS computer, cruise control, etc).

I am trying to think of a simpler solution, and that might be a relay hooked to the brake lights, and another hooked somehow to the tranny lever to signal when it's in park(I am assuming you have a automatic). When it's in park, the relay would complete your circuit, or when the brake pedal was pushed, it would complete your signal. I would assume if you are not in park, or the brake pedal isn't be pushed, you are moving, unless you put it in neutral and set the parking brake, which few people do.

 

After my post I thought of something like this as well, I'll have to think through that a little to see if it'll work.

Thanks.

 

what i would do is find a way to tie into the neutral safety switch - the one that prevents starting except when in neutral or park. doing so would require using that switch to control a relay or two, one of which would serve as a starting interlock as the switch always did, and the other would control your accessory.

but just to clarify your intention, is this an accessory that you want to have come back on every time you pull up to a stoplight, or one you only want to have on when sitting parked somewhere?