I would like to know the following:

I have a motor driving a lead screw which transports a part either up or down. When going down and something comes in the way a switch gets triggered by the obstical which stops the down movement until the obstical is removed (and the switch released). It will continue to go down until it hits an end switch which stops the whole thing. All this works fine. However, now I would like to reverse the motor if something gets in the way. So...if going down, something gets in the way I do not want it to just stop. I would like it to go up for 2-3 seconds and then continue to go down until it reaches the end switch which stops everything as usual.

So...I tried to find a time delay relay and noticed that there are quite a few options. A few I do understand and know I can't use them for my application. The other ones....I have to admit....I don't really understand how they work.

Could somebody be so kind telling me what kind of time delay switch/relay I have to choose and how to integrate it in to my current circuit.

BTW a programmable timer will start the down movement if in "on" mode. If timer turns off the motor reverses and the part goes up. Everything is 12V. A DPDT relay reverses the motor.

I hope I gave all necessary info necessary.

Thanks a lot!!!


1 Answer 1


The simplest way is to use the drive mechanism itself as the timer. Have a DPDT switch which reverses the motor when it hits an obstacle, and arrange the coupling so that the switch doesn't turn off again until the mechanism has backed off a bit. A micro switch with a long lever arm may do it.

If that doesn't provide enough delay or clearance then you will have to use a timer. This would be switched on by the obstacle detect switch, then operate a DPDT reversing relay for 2~3 seconds. Here's a suitable timer:-

Kemo 113A Time switch

Depending on how your existing relay is wired, you may be able to use it for both jobs. The timer outputs would be wired together so that the relay turns on (or off?) to reverse the motor if the obstacle timer is running or if the down timer is finished.

  • \$\begingroup\$ Bruce, thank you very much for your answer. I really appreciate it. I think I will try it first with a second DPDT and lever switch. If this does not work I will try it with the timer.One more question....what kind is this timer relay? I read about all kind of time delay relays like "On-Delay", "Off-Delay", "One shot" or something like that. So what kind is the Kemo switch? \$\endgroup\$
    – wiggi
    Commented Nov 6, 2014 at 16:06
  • \$\begingroup\$ The Kemo 113A is a 'one shot' timer. \$\endgroup\$ Commented Nov 6, 2014 at 18:02
  • \$\begingroup\$ Thank you. I tried to "wire-in" the second DPDT but I just can't get it right it seems. Could you tell me how to connect the second DPDT? \$\endgroup\$
    – wiggi
    Commented Nov 9, 2014 at 21:25
  • \$\begingroup\$ electronics.stackexchange.com/a/107221/49222 \$\endgroup\$ Commented Nov 9, 2014 at 23:46
  • \$\begingroup\$ Never mind. I will get a one shot time delay relay. I hope I can wire that one in...Thanks a lot for all your help !!! \$\endgroup\$
    – wiggi
    Commented Nov 10, 2014 at 19:15

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