continuous timing circuit

Discussion in 'The Projects Forum' started by inspector4, Jan 10, 2010.

  1. inspector4

    Thread Starter New Member

    Jan 10, 2010
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    Hello, I'm not well versed in electronics and have been looking for a variable timing circuit that when turned on will cycle continuously for anywhere from say 5 to 15 seconds. The object is to rotate a motor driven wheel 180 degrees, shut off for the specified time then repeat this same action until shut off. The original device was a 1917 design for a mechanical traffic signal using alternating flag arms for stop and go. This will be a miniature version that will hopefully be driven by a 9 volt battery (if possible). My basic thoughts are to perhaps use posts 180 degrees apart on the wheel that will operate switches/contacts to shut down the motor and activate the timer delay and then reactivate the motor for another 180 degrees. There could well be some inexpensive timing device out there that would be small and suit the need, but I do tend to quickly get lost when looking at circuits that don't have a lot of plain english explanation attached.

    Thanks
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Message wiped out , second time in two weeks, to late to reserect it tonight ,but will try for thumbnail.
     
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    This might do what you wish. The 555 IC is used as a one-shot, ie one pulse out[pin3] for each trigger[pin2] . The wheel will have 2 small bar magnets at 180 deg spacing on or near rim which will activate reed relay[SW2]. Power is supplied by SW1. 555 is reset with pin 3,output, low, allowing base current to flow into PNP transistor, turning it on, motor turns bringing a magnet near SW2, bringing pin 2 low triggering 555, pin 3 goes high shutting off motor for duration of timing cycle. Small problem: as pin 2 is still held low 555 cannot re-set; need to add differentiator between SW2 & pin2, 10k in parallel with 10k at pin 2, put a .iuF cap between two resistors on SW lead.Now 555 will reset, turning on motor untill next 180 deg.Transistor selection depends on motor selected. If motor draw is under 200mA, transister may be eliminated, with other minor changes. Any questions?, ask away.
     
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