Auto-off for car dome light

[nologic]

Once in a while I left the car dome light on and the battery becomes drained or semi-drained the next day.

I want to add an auto-off circuit to the dome light so the dome light would turn off after about 5 minutes. When the light is off, the timing circuit should draw less than 5mA.

The timing should be adjustable and does not need to be precise.

There is no button or switch in this circuit. It is simply reset when the power is turned off (e.g. car door closed or light switched to OFF). So if the dome light is on for 5 minutes and the timer kicks in and turn off the light, I can switch the light off and on (using the car's dome light switch) and get another 5 minutes of light.

The light itself would draw anywhere from 50mA to 1A, depending on what light bulb/LED I replace it with. Car voltage is standard 12V.

I'd like to know if there's existing product to do this? Someone already posted a circuit to do this somewhere? Or, someone could point me to an IC that can help me do this?

 

[milan.rajik]

Can it be 8 pin PIC microcontroller based ? In terface a vibration sensor fixed to Car. If vehicle is moving then lights can be turned ON. If there is no movement of vehicle (that is no vibration for 5 minutes then lights turn OFF. It will be powered from Car battery directly but with a switch. It will have a relay in series with car ignition switch. If no vibration for 5 minutes then ignition is turned OFF irrespective of whether ignition was ON or OFF.

 

[BradtheRad]

I once made a similar project for our car, so the dome light would not accidentally drain the battery any more.

It used a 555 timer, relay, and large capacitor, 200 uF. The large capacitor allowed a 3 minute timing period.

It had only two wires. I installed it in the dashboard inline with the switch. It did not draw power until the switch was turned on. My project needed to be wired in the circuit directly, because I did want to wire it through the fusebox. I realized it had to get power even when the ignition was off.

I was just lucky that I could get access to remove the dome switch. It was a chore to install my circuit. I was just lucky there was enough space for it to fit.

The relay kept the light on for 3 minutes, then off. Very good. But then if the switch was turned off and on, the circuit kept the light on indefinitely.

So my project did not work perfectly. I think it had to do with the capacitor keeping its charge for a while after shutoff, and what point the trigger signal was applied to the 555.

 

[kam1787]

This is the basic idea http://www.bowdenshobbycircuits.info/page2.htm#relay_i.gif I would replace the relay with the load [for say LED lighting]

This is for longer delay http://www.eleccircuit.com/on-after-delay-with-mosfet/ use a higher power transistor or power darlington

there are many commercial modules - use google or bing; "power off delay 12V"

 

[milan.rajik]

See this circuit.

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Try attached .hex file. Proteus 8.1 SP1 simulation file attached. When there is no vehicle movement for 5 minutes the lights and engine turns OFF and PIC enters sleep state. If vehicle movement (vibration) is detected then enables ignition switch and turns light if it was already ON.

Select the right relays from here.

**broken link removed**
https://www.goodsky.co.uk/products.php?model=AR&search=Go

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You can use this vibration sensor.

**broken link removed**

If engine is ON then there will be vibration and so lights will be ON if they were already ON but engines doesn't auto turn OFF in this situation and hence if engine and lights are kept ON then lights will not turn OFF automatically.

Edit: I found a solution.

Ig engine is ON then there will be vibration. So, if engine is ON for more than 5 minutes and gear lever is in neutral position (gear switch sense) then turn OFF engine and also any lights.