timer circuit

Discussion in 'General Electronics Chat' started by SonOfAnarchy ZA, Feb 14, 2013.

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  1. SonOfAnarchy ZA

    Thread Starter Member

    Jul 13, 2011
    Hi guys So i need some help designing a timer circuit using a 555 ive seen a few threads on it but would like to get a fresh opinion.

    what i would like to do is design a timer circuit that can stop a motor(12v to 14v system) via relay after a preset time but it need to fairly accurate and have fine tuning. The time that the motor goes from top to bottom is around 1 second so the timer needs to be able to have split second resonse.

    would a 555 be able to do this application for me?

    I have made a 555 circuit to pluse an input of a counter ic in a previous project but for this one i need a single output and a reset.
  2. shortbus

    AAC Fanatic!

    Sep 30, 2009
    Just my thoughts on this type of question/circuit. Using a timer to stop a motor in a certain position is not a good idea. It may work when every thing involved with the motor and mechanical part are working perfect, but does not allow for any of the normal things that happen in real life. By that I mean, lower than normal voltage to motor, something getting in the way of the mechanism, higher than normal load in the mechanism, ETC,ETC.

    Limit switches are a much better option than timers for positioning or stopping a motor/mechanism at a certain position.
  3. tshuck

    Well-Known Member

    Oct 18, 2012
    This application would certainly benefit from a controller. Depending on the size of your motor, load inertia, momentum, etc, it may require you to employ some sort of braking. Positional feedback, via encoders, of some sort help determine where your motor shaft is. If you want to stop your motor at a certain position, you need a way to determine its position.

    You can't expect to control a device with an open-loop control system(no feedback). Your system needs to be able to sense where the output shaft is. As shortbus pointed out, there are many things that will change as you use your motor, you will not be getting the same behavior, so you must be able to compensate for those discrepancies as they happen.

    What is your application?
  4. SonOfAnarchy ZA

    Thread Starter Member

    Jul 13, 2011
    thanks for the reply's guys but its not a huge motor or heavy load. the application is on my cars pop up lights id like to stop the at a certain height and id like to be able to adjust the height the timer circuit will just disconnect a wire from the switch thus stopping the motor.
  5. Georacer


    Nov 25, 2009
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