Evening All,

I need to build a simple circuit to power a motor (10A). I need to power the motor in one direction until it hits a limit switch and then in the other direction until it hits a limit switch.

Ideally wish to power it using one dashboard mounted switch. How can I wire a circuit that not only switches the polarity for forward and reverse but cuts the power when it reaches each of the limit switches?

When it hits the limit switch I don't want anything to be energised (relays) as it may be left in this state for a period of time.

Any advice would be most welcome.

Thanks,
Steve

What are you trying to do with the motor?

It's driving a linear actuator.

do you want a push button sort of thing to move it, then the same button again to move it back? Or rocker style either way?

id have a pair of double pole switches, both linked up to the motor, but only one working at once, and have them wired opposite ways round. Make both of them turn of when the current is interupted (ie no voltage release switches, held on by electro magnets), and devise a simple mechanical device (like a biro) to alternate which switch is activated.

the limiter switches would be normally closed and spring loaded.

[Edited on 1/3/06 by JoelP]

That is the sort of thing i need. I think it may be simplest to use two switches. It's just that I would have prefered just the one.

thanks,
steve

some questions.

When it reaches either limit switch, motor stops?
What happens if you press and immediately release the dash board switch? Does motor stop or continue until it hits limit switch?
If motor stops before reaching limit switch, e.g. you turn off igntions, in which direcion does the motor go? Does it need the
dash switch to be pressed to make it move? And if so, again in whcih direction?

Hi Steve,

My scanner is u/s at the moment and I am not up to doing circuit diagrams on a computer yet. However if you send me a u2u with your snail mail address I will have a circuit diagram in the post tomorrow for you.

You will need one,single pole, single throw switch as the control, one double pole, double throw 12 V relay and two micro switches as limit switches.

Dead simple to do.

Sorry I was lying before..
You need; One single pole, single throw switch to isolate the supply, one double pole, double throw switch as the control and two micro switches for the limits. No relays, forgot that it was not to be under power for extended time.

Circuit in the post.

robocog

Just had a peep at your site. Nice graffics.
Yes your circuit will work OK. A good rule of thumb, so to speak, is have both your limit switches in the +ve circuit. Then you know that when it's stopped, there is no power to the motor. Doesn't matter much on this, but if you were using higher voltage or mains, it could prove very interesting. You would be supprised how many people assume, that if a motor has stopped there is no power to it. This is why it is normally illegal to switch neutrals in mains wiring ( with certain specific exceptions ).
Interesting project though. My uncle used to be a 2 metre freak. He had some awesome kit.