Advice on sensor switch

Thread Starter


Joined Jun 19, 2020
Hi I would like to fit a sensor switch to a machine in my catering van. The machine is a 12v machine.

I would like to start the machine using the sensor switch and would like to work for 60 seconds. Once 60 seconds have passed, I’d like it to turn off.

however, it gets a little more complicated,I would only like it to turn off, if there is no power going to compressor (again 12v). If the compressor is getting power, I’d like to leave the machine on.

so once the sensor switch start, the machine would turn on:

it should only turn off if 60 seconds have passed and the compressors is NOT getting power.

If the compressor is getting power, the machine should stay on, until it stops getting power.

....And it gets more complicated...
Above a certain temperature inside the machine, I would like it turn back on, the compressor will automatically kick back in.

Any ideas, and knowledge in how to set this up will be much appreciated. Ideally it will be a reliable system and have no circuit boards.

I will also have a bypass switch so I can control the power to the machine and compressor manually.(This is how I currently control the machine.)


Joined Jan 8, 2017
I think it is going to be rather large with your requirement of "no circuit boards" For example the 60 second timer would have to be based on a geared motor driving a cam or some kind of clock mechanism. Can we assume that the output of the "sensor switch" is just a set of contacts closing when the sensor switch senses whatever is is sensing ? Until I read your requirement for no circuit boards I was going to suggest using a microcontroller. That together with some devices (Relays power MOSFETs etc.) to do the actual switching would make it very simple.


Thread Starter


Joined Jun 19, 2020
The senor I had in mind is a motion sensor/infrared sensor to detect hand movement informs of it.

I think I wasn’t being reasonable saying no circuit boards, but, I’d prefer it. This is because the machine will be used all day and generates heat, so I’d like something which is reliable. Thinking about it now, I will need a circuit board for the 60 seconds.


Joined Jul 18, 2013
You could look at a Smart Relay, they come in a 12v version.
They are programmable and have a few internal timers,
But requires a little programming knowledge.