Need help with adjustable timer

Discussion in 'The Projects Forum' started by fragglerocks, Mar 3, 2010.

  1. fragglerocks

    Thread Starter New Member

    Mar 3, 2010
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    I have tried to see if there is a similar post online for a few weeks now and have not been able to find one (or one that I understand). So if this is a repeat I apologize ahead of time. I have the following:

    12v input
    12v output
    18awg wiring

    I need:
    to be able to delay this signal with a potentiometer(I assume) so the signal can be delayed and adjusted between 20milliseconds and 100 milliseconds.

    I would prefer:
    simplicity (radio shack parts)
    cheap and small

    Any help with this would be great. It seems as though I could do this with the pot, a cap, and relay (maybe???) but i don't know what size items i need (this is where it goes over my head. The Uf and Ohm items). Thank you ahead of time with any and all help on this.
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    You missed some core information. What is the load?
     
  3. fragglerocks

    Thread Starter New Member

    Mar 3, 2010
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    Forgive my stupidity on this. When you say load, are you referring to amperage? If so I will measure that tomorrow. If it helps this is in a standard 12v automotive application off of the ignition switch (30 amp fuse) that the signal is coming from.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    So what is the signal feeding? On these kinds of querys you can't have too much information.
     
  5. retched

    AAC Fanatic!

    Dec 5, 2009
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    Is the end item a light bulb? a radio? a motor? Windshield wipers? Window motor?

    The load is what is connected and the draw is the amperage.

    You want to have something powered 20 milliseconds after the ignition is powered, what is that thing?
     
  6. fragglerocks

    Thread Starter New Member

    Mar 3, 2010
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    It is powering an air valve (parker). this is for an air actuator. I need to be able to delay the signal after a button is pressed (for shifting purposes). The valve is 4.5w 12vdc. Model number is xm30nbg45a. The goal is when the button is pushed on the dash that the signal coming to the air valve is to be delayed as described above before the air actuator moves.
     
    Last edited: Mar 4, 2010
  7. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Untill something better comes allong: A 1A N ch MOSFET, 1 uF cap, 100k pot & 555 IC. NO sw contact to +cap, pins 4&8 of 555, +valve. -cap to pin 2 & pot wiper. Pin 1 to ground. Pin 3 to gate. Source to ground. Drain to - valve. one end of pot to ground. When power is applied, pin 2 is held hi for about one RC time, adjustable. When cap charges, V at pin 2 falls, causing pin 3 to go hi, turning on FET. Might bypass C with 1 meg ohm resistor to discharge C at power off.
     
  8. fragglerocks

    Thread Starter New Member

    Mar 3, 2010
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    is this the mosfet item:

    http://www.radioshack.com/product/index.jsp?productId=2062618

    I have never used one of these. I would like something simpler than what is described if possible. I think i can make what is described but i will have to ask a few questions about the connections to be made since it seems a little confusing to me right now. thanks again.
     
  9. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    IFR510, not great but OK here. 5.6 A, 100V, RDS .54 ohm. N ch MOSFET. Face up, hole down, gate-right, drain center, source on left. Would add diode in parallel with valve, cathode to + supply for V spike protection. If you can draw schematic from the post, then we bet that you can make it.
    How long does valve stay actuated??
     
  10. fragglerocks

    Thread Starter New Member

    Mar 3, 2010
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    The valve (which moves the actuator) is instant. It is for shifting the transmission so the signal (once going through delay) would be an instant activation and them back off. You could hold the button down to keep the actuator in up or down position but you would never need nor want to do this.
     
  11. ozarkdan

    New Member

    Jan 11, 2010
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    You can use a 555 timer from the shack, and have it drive one of their 12V relays. This website will help you with component selection for the timer.

    http://home.cogeco.ca/~rpaisley4/LM555.html#3

    The 555 can drive up to a 300mA load. For more current, use a 3055 transistor.
     
  12. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    With a short delay on 555 powerup, circuit works as envisioned. Added 22 ohms between pin 8 & SW-NO; 1 uF pin 8 & ground. When pot is at56k ohm, delay is 100ms, @ 11k it is 20ms. One uF timing cap measured 1.3 uF. If using NPN transistor rather than FET, add 360 orms between pin 3 & base.
     
  13. fragglerocks

    Thread Starter New Member

    Mar 3, 2010
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    Ok. So what I understand at this point is this (hopefully my ignorance on the subject and my mistakes that followed are tolerated):

    Pin 1: Ground
    Pin 2: 100K Pot (just one leg, other leg is to ground) then to 1 uFCap to button on dash (12v signal)
    Pin 3: NPN transistor & 360 ohm resistor(I think i have this wrong)
    Pin 4:
    Pin 5:
    Pin 6:
    Pin 7:
    Pin 8: 1uF cap to 22ohm resistor to ground
     
  14. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Hope I do not muddy the water even more. Call all conections to NO sw as +V
    Pin 1: ground
    2: - side of 1 uF cap, +end to +V, & center contact of pot, one end to ground,
    3: 360 ohm resistor, other end to base.
    4: +V
    5: NC
    6: NC
    7: NC
    8: + end of 1 uF filter cap, -end to ground;& 22 ohm to +V.
     
  15. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Printer back up??
     
  16. fragglerocks

    Thread Starter New Member

    Mar 3, 2010
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    Ok. I think all makes since to me now. I am off to the shack and frys to get the parts and test them this weekend. I will let you know how it goes (fingers crossed).
     
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