Relay (substitutions)

Discussion in 'General Electronics Chat' started by mik3ca, Feb 25, 2008.

  1. mik3ca

    Thread Starter Active Member

    Feb 11, 2007
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    0
    I want to be able to control my room light using a low voltage circuit. For example, If I were to make a common astable multivibrator (which I can make), and take the output from it and control a 120 volt lightbulb, I can see me doing it using a relay and excessive current every time the light is on.

    What I want to do is avoid the need of excessive current, and use something different instead of a relay because the contacts of a relay will wear out after a while and it might no longer work.

    Can someone help me on this?
    thanks.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Mike,
    Your idea won't work, as the relay can't switch fast enough. Additionally, the constant switching will rapidly burn out the contacts.

    I am concerned that you're considering experimenting with 120VAC circuits. 120VAC can get you killed very quickly. Save that kind of experimentation for a few years down the road, and stick with circuits under 45V for now.

    Still, you might find the X10 line of products interesting.
    http://www.x10.com
     
  3. mik3ca

    Thread Starter Active Member

    Feb 11, 2007
    189
    0
    That's why I wanted to know if there is something I could use instead of a relay.

    The 120VAC part is going to be isolated from the rest of the circuit, which means off the top of my head, I could use an optocoupler or a relay, or something equivalent that I don't know about. For now, I will only deal with my light switch, so that under the worst case scenario, the light goes on instead of a short circuit.

    That's what I have been doing for the past 5 years trying to get my radio going. Now my radio is working almost 100% perfect. I get a slight whitenoise mixed with my station (Z103.5), but I can hear it well.

    I understand safety is important, which is why my first victim is a light switch instead of a wall socket.

    Now I'm tempted to use an optocoupler, but I don't know if it can handle 120VAC. I'm going to go check datasheets.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    What you want is an SCR or a TRIAC.

    They are commonly used in dimmers, along with some associated circuitry.

    Once they are turned on, they stay turned on until the current throught them drops to zero. In the US, this happens on line power 120 times per second.
     
  5. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    You can read up on TRIACs and SCRs here in the AAC ebook.

    hgmjr
     
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