motor running indicator

Discussion in 'General Electronics Chat' started by raffter, Apr 3, 2008.

  1. raffter

    Thread Starter Active Member

    Feb 28, 2008

    anyone got ideas how to go about having an indicator if a motor(220VAC) is running??

    its for a clothes drier.. sometimes its stuck up and wont run unless you give it a spin...


  2. SgtWookie


    Jul 17, 2007
    It would be far better if you determined the cause of the "sticking".

    AC motors usually use capacitors to start and run. Some of them have a switch that is operated by centrifugal force; selecting one capacitance for starting and another for running. If you used to hear a "click" when your dryer started up or turned off, it's of this latter type.

    It could be that there is a build-up of lint in the motor, due to air leaks in various areas of the dryer. It could also be that the contacts are getting burned, or the capacitor has failed or is severely degraded.

    If your motor has ingested lint, there is a strong possibility that it will soon overheat and burn out due to the lack of airflow for cooling.

    But if you just want a cheap "running" indicator, put a pair of tennis shoes in with the clothes. The thumping they'll make will be a pretty positive indication.
  3. raffter

    Thread Starter Active Member

    Feb 28, 2008
    using tennis balls????? :D IF I where not DEAF, then THAT would be applicable :)
  4. SgtWookie


    Jul 17, 2007
    Oops - tennis SHOES, not tennis BALLS - tennis balls would probably explode!

    I did not know that you are deaf. All the same, if you an old and clean pair of tennis shoes in the dryer, you should be able to feel the vibrations as the shoes tumbled if you put your hand on the top. But that is obviously, that is a temporary solution.

    I haven't had my coffee yet, but the first thing that came to mind is to fasten some magnets around the outside of the clothes drum, and make up a bracket to hold a magnetic sensor, such as a reed switch or Hall-effect device. Then use the switch or Hall-effect device to connect/disconnect power to an indicator, such as an LED or neon bulb. An incandescent bulb would not last very long, as they don't like to be turned on and off rapidly, and they also use a lot of current.

    Neon bulbs need at least 55 volts to "fire", and need a resistor connected in series to limit the current - but they are simple, and long-lasting. An LED will require a low-voltage DC supply.

    One problem is the heat inside the dryer. This is stressful on electrical and electronic components.

    Something simple - cut a hole in the top of the dryer, and fasten a piece of plexiglas over the hole. You could then use a flashlight to look in and see if the drum is turning. Of course, you can just open the door really quickly and close it - but that often causes the drum to stop turning, which is counter-productive.
  5. techroomt

    Senior Member

    May 19, 2004
    i agree with the "find the problem" advice. will probably take less time then building a monitor device. you lilely have a poor connection somewhere. if it uses the old mechanical timers, the problem is probably in there. i have had luck with opening them up and rebuilding contacts, look for the blackened ones. check on the motor for power when it is supposed to be spinning, and follow it back. if power is there and it's not spinning, it's your motor.
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    May we assume your drier is the kind that requires you to depress a button for a period of time? And if the button is not held quite long enough then the drier does not continue to run?
  7. h.d

    Active Member

    Oct 22, 2007
    put led parallel with the contactor of motor
  8. raffter

    Thread Starter Active Member

    Feb 28, 2008

    IM not DEAF( im only 31) :)

    my father is half -deaf....

    our washing machine(asian built) has 2 motors... 1 for the washing and another for the drier(and has 5 minute timer, mechanical/spring etc)...

    it has also a "kill" switch that when the LID is open, the motor will be off...

    my father wont know if it(motor) has been running OR the switch has STILL NOT enabled the spin motor, until I really slam the LID shut ...he assumes the motor has spinned already...

    I dont know if there is such a circuit w/c lights(LED) when the motor IS spinning already.. maybe a detector for back EMF? etc etc...

  9. hgmjr


    Jan 28, 2005
    Greetings raffter,

    I found this circuit on a website that I frequent. Take a look and see if it suits your application.

  10. raffter

    Thread Starter Active Member

    Feb 28, 2008

    thanks!! that could be it.. :)

    maybe a plain old 741 in place of the LMC7215(cmos) ..... or maybe a jfet op-amp for less current draw..


    ooopppsss.... turns out the op-amp used is a comparator... :)

  11. DC_Kid

    Distinguished Member

    Feb 25, 2008
    tape/glue a magnet to the drum (outside), then mount a proximity or reed switch close by. switch drives small relay which in turns drives a led or light, etc. as drum turns (if turning) you'll get flashing light, otherwise no light.