# micro-switch 12V DC use in vehicle?

Using 12V DC (max 3 amp) linear actuator in a standard car, I need to use some micro-switches in the power circuit to prevent the actuator powering, if it's not in the correct position i.e. won't start until it is in a position where the micro-switch is closed.

Looking at ME-8111 whose specs say:
AC-15 Ue: 250V, le: 6A
DC-13 Ue: 220V, le: 0.3A
My question is: Will this switch work fine? (The 0.3A bit gets me.)

Thanks for any insight. I've googled and read so much, but still don't know the correct answer.

I'm assuming it means it only can carry 300mA or 0.3A at DC voltages. So you cannot use these directly with your actuator. You would need a circuit to take those switches and control a relay/mosfet/transistor to control the actuator.

• Thanks for the reply i was trying to minimize the circuitry on this project so trying to ovoid relay's etc. might have to look at a different approach. Jun 23 '19 at 3:33

Can you directly control the driving power with only two switches? If the actuator is powered via only two wires where polarity determines the direction of motion, interrupting one or both wires via switch e.g. at the "low" position will disable any motion of the actuator, i.e. it will not be able to move away from that position again.

You may be able to work around that problem using one diode across each switch, effectively bypassing that switch for one direction of current.

Also note that the DC current rating for mechanical contacts is often significantly lower then the AC rating. Check the datasheets, or derate the AC current limit by at least 50%, much more if your load is/has a big inductance.

There are two currents for a relay, the carry current, and the breaking current.

The carry current is dictated by the thickness of wires, the contact area in good contact, and by the resulting $$\I^2R\$$ heating that occurs. This should be independent of AC or DC current flowing through the relay.

The breaking current is dictated by how fast the contacts extinguish an arc as they open, and as a result, how much damage that arc does to the contact surfaces. The factors here are contact opening speed, contact material melting point, contact heat capacity, and whether the input current is steady, or goes through zero many times per second (DC or AC respectively).

As your switch can carry 6A of AC, I see no reason why it shouldn't also be able to carry 6A of DC, provided that it's never called upon to control that current. If this switch works purely as an enable, and the switch off is done by some other switch, say a travel limit switch or control switch elsewhere, then you should be able to use it.

Although it might appear that switch on is far kinder than switch off, bear in mind that contact bounce means that switch on is usually followed by a switch off mS later, and then a few more bounces, before it settles on. If the current has built in that time to a damaging level, then contact damage will be done.

• Thanks Neil Just to clarify the position in the circuit of the switch is just to stop the current Basically working like a standard light switch setup off and on When the switch is “on “ then the full working current of the actuator ( 12vdc 3 amp) will be passing thru the contacts. I think this is what you are saying it “can’t or shouldn’t ) do. Do I need to get a higher amperage switch? They aren’t very common ip65 rated Thanks Jun 23 '19 at 5:53
• The states of carrying the current and blocking the current are OK. The actions of starting the current and stopping the current are not OK. Will the operation of this switch ever start or stop the actuator? Jun 23 '19 at 6:05
• Neil it shouldn't as the actuators are controlled by their own controller box. the microswitch is there to prevent the actuator starting unless it is a "parked" position. ie the contacts would be closed. once parked the controller would supply power through the switch to activate. Jun 23 '19 at 20:16