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5v - 24 vac Relay for Ventilation Controller Project? — Parallax Forums

5v - 24 vac Relay for Ventilation Controller Project?

Carl JohnCarl John Posts: 2
edited 2006-03-17 16:19 in BASIC Stamp
I have a project idea to build a ventilation controller for a residential furnace system.

This controller would open/close a 24vac motorized damper to allow/disallow outside air into the return duct of a forced air furnace system.

I would like to avoid actually powering the motor with the basic stamp, so I have a 120VAC/24VAC transformer.

My question is, do they make a relay that can be energized with a 5v signal·from the Basic Stamp 2 that will simply close the circuit to allow the 24vac through to the motor?

If not, would I need to provide a resistor,transistor,diode and then relay to bump up to a higher voltage (24vac) to control the motor.

If the latter, then I suppose I can eliminate the transformer and just power through the basic stamp.

Any input would be appreciated. See attached diagram for my proposed circuit to connect to the damper.
pdf
pdf
DamperControllerDiagram.pdf
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Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-03-16 16:32
    Sure, you could use an SSR like this: http://www.parallax.com/detail.asp?product_id=400-00010

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    Jon Williams
    Applications Engineer, Parallax
  • Carl JohnCarl John Posts: 2
    edited 2006-03-16 17:02
    Thanks for the reply - that is very helpful.

    If I didn't have the transformer and therefore alternate power supply, could I use this relay to "bump up" the basic stamp output to power my load?

    Sorry, haven't done much besides low voltage DC control.
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-03-16 17:08
    That relay is simply an A/C switch -- it matches the requirements of your diagram. The nice thing about SSRs is that they take a low-current, low-voltage control signal, so you can use a pin right out of the Stamp. That particular relay with switch voltages up to 240 VAC, so you have a lot of latitude with it.

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    Jon Williams
    Applications Engineer, Parallax
  • JohnnyBJohnnyB Posts: 13
    edited 2006-03-16 18:17
    Jon,
    Could that SSR be used to replace an SCR in some cases...where the SCR simply functions as a switch?
    Do you know what frequency it can handle?
    Thanks,
    JohnnyB
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-03-16 18:22
    An SSR uses a triac, so it can only control AC; it will turn on DC, but the control signal won't matter once it's on -- it will stay on until the AC power is lost. That said, there are DC versions (SCR) of those relays. Have a look at the Crydom web site for details and specifications on those products.

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    Jon Williams
    Applications Engineer, Parallax
  • JohnnyBJohnnyB Posts: 13
    edited 2006-03-17 16:19
    Thanks Jon,
    JohnnyB
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