power a 120v relay from a triac timer?

Discussion in 'General Electronics Chat' started by lorenzop, Jul 2, 2009.

  1. lorenzop

    Thread Starter Member

    Jul 2, 2009
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    I have a brinks in wall timer from walmart hooked up to my front porch light. it works ok, but it's in-line, and uses a triac for switching. I also have it wired to out door outlets in the roof to put christmas light on that same timer. right next to that outlet is another outlet with a photo sensor hooked up to it to plug in a bug zapper. the photo sensor has it's own neutral leg for power, and uses a relay for switching. what I want to do is use a 120v relay with the coil plugged into the timer outlet, then the contacts of the relay hooked to the photo sensor and to a plug for the bug zapper. the timer turns off at 2am. I want the bug zapper to only be on between 2am and sunrise. same problem as using a cfl on a triac, it flickers. I plug my relay into the outlet and it flickers too. how can I fix this? I'd have a problem with it hooked up either way, the bug zapper has a fluorescent bulb in it and flickers when plugged into the timer. how can I power either the relay or the bug zapper from the wall timer?
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    2,535
    You could use a relay, or your could use a SSR. The timer triac is exactly like a relay in it's application, but is probably limited in current. You just use it like a switch for a larger relay.
     
  3. lorenzop

    Thread Starter Member

    Jul 2, 2009
    12
    0

    yeah, I'm trying to use a relay with a 120v coil rating. you know how compact fluorescents flicker if you put them on a light dimmer? that's the same thing that's happening with my relay on the timer. it just keeps clicking on and off. it works perfectly if I add an incandescent bulb to the circuit, but that defeats the purpose. I want to be able to turn off the porch light and have the relay still working right.

    I think the problem might be that the relay restricts to much current from the timmer, and the triac shuts down when the ac voltage is near 0v. I think the right size resistor and high voltage capacitor in series, hooked up at the relay's coil, would allow a little more current past the relay. enough for the timer to work right. but I don't know if this is safe, or what values to use.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    Just connect the output of the timer to the relay coil, and then use the relay contacts as a conventional switch. This project has some danger to it, being you are dealing with house currents, so put this sucker in a box (and be careful). I get the feeling you don't know too much about house current, it may be better and cheaper to buy a different timer, one with a better switching arrangment. The several I've bought over the years tend to use light weight relays.
     
  5. lorenzop

    Thread Starter Member

    Jul 2, 2009
    12
    0

    I'd prefer one with a small relay in it, but it's tough to tell just from looking at the package or even a manual. don't worry, I have plenty of experience as an electrician and a programmer. I don't think anyone understands my problem yet. I plug the relay's coil into the timer outlet, but it doesn't draw enough power to keep the triac powered up inside the timer. if I also plug in a normal light bulb into the same circuit as the relay then it draws more power and works fine, but I want it to work without having a light bulb on. the relay just keeps clicking. what I think I need is a resistor and capacitor in series to simulate a light bulb but not put off any light. just to pull a few extra milliamps and allow the timer to work right. I don't know what values to use or if it would work as imagined, so I was seeking advice from someone with experience. basically, how do you simulate a light bulb on a light dimmer without the light.
     
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