# Need help designing / understanding this 'circuit'

Discussion in 'General Electronics Discussion' started by Brad Hays, Apr 21, 2016.

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Sep 24, 2015
I'm a novice builder of whatever I can imagine with not a lot of formal training in electronics, but I follow directions well so I imagine I have a good chance of pulling this off with the right advice.

Here's the deal...

Keeping it simple, I need to turn on electricity to a 1500 watt device (heater) when a mechanical circuit I've made is closed. But I don't want to run 1500 watts through the wire I've used to create the mechanical circuit. so I'm writing in for advice on how I should go about doing this.

The design is that once air is ran through a vent, a flap is actuated which moves and creates contact with two wires, and I need to figure out how I can convert these two wires coming into contact into turning on power to a 1500 watt heater (without running 1500 watts of current through the two wires on the vent flap. So is what I'm talking about here called a 'relay?'

Like I was saying I'm now trained in electronics so I would need somewhat detailed instructions on how to go about making this happen.

Thanks for your time I'm all ears!

2. ### Harald KappModeratorModerator

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Nov 17, 2011
A relay (rated for mains voltage and enough current for your heater) is one simple solution. You connect the low voltage coil to the contacts of the flap using an appropriate low (safe!) voltage source. When the contacts of the flap close, this low voltage forces a current through the relay coil which in turn will actuate the contacts on the mains side.
The relay coil neds to be rated according to the low voltage you use for sensing the flap's state.

3. ### Colin Mitchell

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Aug 31, 2014
If you need to keep your marijuana crop warm during the cold nights, you can go to your local hydroponics suppers as they have exactly what you need.

4. ### Alec_t

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Jul 7, 2015
A lever-actuated microswitch could do the job without the need for a relay or any electronics.

5. ### Harald KappModeratorModerator

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Nov 17, 2011
Yes, but the op stated explicitly:

6. ### Alec_t

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Jul 7, 2015
With a microswitch operated by flap movement there wouldn't be any need for wires on the flap.

7. ### Harald KappModeratorModerator

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Nov 17, 2011
Right, but wires leading to the flap. I can ony assume that the wires present are of small diameter and not suitable for powering a 1500W load. Just a guess, of course.

8. ### 73's de Edd

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Aug 21, 2015
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Sir Brad Hays . . . . . . .

You have just received the methodology of being able to switch on /control your heavy 1500W device by placing a large power relay / contactor at its side. and then using a low voltage . . .usually
24VAC . . . . to actvate its coil. That then gives you the capability of switching that 24 V from 25-50-75 feet away with a run of small gauge wire.

The needed info not coming forward YET is the refining of the specifics of :

air is ran through a vent, a flap is actuated which moves and creates contact with two wires,

Also, the " creates contact with two wires," has been covered by the use of a mechanically proper switch type , connected in, and able to respond with the DEGREE of strength being continually exerted against it by the hanging flaps response to air flow .

Now the fuzzy part is being the source of that air flow, is it from a blower that is right in a room?
Or
Is it a blower that dumps into duct work and then exits X ? feet away into a vent where that detecting flap is located ?

How does the application of the heater fill in ?
Is it merely down in the room that the incoming air is entering into, and just needs to be turned on when air flow is sensed.

Or
Does the heater need to introduce its heating into the air flow path just prior to the exit vents position,, or possibly back near the blowers introduction of air into the ducting?

In two of your older posts, which you never responded back from, the distance was being 40 feet and it looks like you have now upped your techno expertise horizons, from it then being a buzzer alert , to it now being a 1500 watt heater.

73's de Edd

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Last edited: Apr 21, 2016