12v current timer, delay box

Discussion in 'General Electronics Chat' started by chaz6966, Sep 26, 2006.

  1. chaz6966

    Thread Starter New Member

    Sep 26, 2006
    3
    0
    i have two circuts running off of a delay box, i want one circut to get current longer than the other one. the delay is set for .975 seconds that releases the trans brake sylenoid, and a rev limiter at the same time, i want the rev limiter to be energized for .25 to .5 sec longer after the deley box has timed out. is this possible?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    Got a schematic of the delay box? Can't tell from your post if it's adjustable. Otherwise, you'll need another box to do the trick.
     
  3. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    Yes, anything is possible with electronics :)
    But... What are the output from the delay box ? Is it B+ or ground until timed out or what ?
     
  4. chaz6966

    Thread Starter New Member

    Sep 26, 2006
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    0
    trying to do something without buying another delay box@300.00 if i had a length of wire say 100ft long and it takes .25 sec for current to pass from one end to the other, then .25 sec to run out of ppower. is there a way to use a 3" piece of wire and get the same results.
     
  5. chaz6966

    Thread Starter New Member

    Sep 26, 2006
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    what im trying to do is have a 3" long piece of wire that is energized and after the power goes off a capacitor will keep the rev limiter energized for .25 seconds longer than the delay box after it times out. but i dont know if a capacitor is what i need or not, and or how to know what the time span of it might be
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    Without some spec's or a schematic, I can only shrug. There's no way to tell how much power it takes to energize the rpm limiter. A capacitor is not going to do the job, though.
     
  7. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    567
    12
    You can determine if a capacitor would work by applying the formula:
    I = C * (dv/dt)

    Assuming you're using a car's 12V battery, you would need to determine a minimum operating voltage (let's say 9 volts) for the delay device.

    The difference (delta or "d") between 12V and 9V is 3V.

    So simply divide 3V by the amount of time you want it to stay on, which is 0.25 Sec (or 250ms) like this: 3V / 0.25 = 12

    Let's assume you have a 10,000uF cap (10,000uF = 10,000E-6 = 0.01):
    0.01 * 12 = 0.12A

    This indicates that you will get 0.12A (120mA) for 1/4 sec (250ms) with a drop in voltage on the cap from 12V to 9V.

    Note that 3V / 0.5 sec = 6 and that 10,000uf * 6 = 60mA, or half the current above for twice the amount of time (1/2 sec).

    If your device uses more current, you will need to raise the capacitance accordingly (or possibly live with a lower operating voltage). If it uses less, you could lower the capacitor value. Just plug in the numbers.


    If you use the above and determine that a cap is not the way to go, then you would need the output of first delay to trigger a second delay to get the post 250ms.
     
  8. jtodd5781

    New Member

    Sep 29, 2006
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    Chaz, you could try adding a variable delay on brake relay to the output of your delay box. These relays are available from Newark Electronics for about $30.00. I am running 2 of these on my dragbike. One doesn't allow the auto shift to activate until approx 1 sec after the delay box times out and the other keeps the shift signal from being chopped when the shift counter hits 5th gear and the auto shift circuit is deactivated.
     
  9. jtodd5781

    New Member

    Sep 29, 2006
    6
    0
    Chaz, I was looking at some of the other suggestions, I don't think any of them will work and your suggestion about using a longer wire is not physically feasible. Electricity travels at approx. the speed of light, so you would need 46500 miles of wire to delay it .25 seconds. I don't know about your bike, but I know on mine that I don't have that kind of space. By adding a capacitor to your output won't work easily, there are too many variables to consider and you would have to isolate the inputs to your rev limiter and your clutch so that the ramp time doesn't effect the other since they are on the same output.
     
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