controlling multiple low-voltage devices with a single relay?

[MikeB]

I posted something similar on another forum, but wanted to post here as well to get some different feedback.

I have a bunch of props I'm looking to use for my Halloween setup this year. Most are controlled via motion sensor, but the motion sensors that are built-in are typically crappy.

I'm planning on using a typical floodlight motion sensor to activate several props at once. My plan is for the motion sensor to power a relay, which in turn will activate the props. The props have low-voltage switches that can be used to activate the prop (like for in-store demos).

My question is, can I use a single relay to activate multiple props at once? If so, what would be the correct way to wire them? I know it's overkill, but I'll probably use a Radio Shack 275-217 since I've used it with success in the past.

http://www.radioshack.com/product/index.js...oductId=2049721

Suggestions greatly appreciated!

 

[mdesmarais]

thats really going to depend on what exactly the LV switch on the device is doing ... . kind of need to know how they are wired.

Might be simpler to switch on all the devices with their LV switches, and then plug all the props into a single power bar, which is controlled by your relay?

 

[JimS]

You will probably have trouble just connecting them all in parallel because they may be different voltages. You may be able to connect them all to one set of relay contacts if a diode is placed in series with each item. You would need to check polarity of each item - should be able to do that with a multimeter across where the switch goes or just place the diode across the switch contacts and see which way trips the unit.

 

[MikeB]

Sounds like the easy solution is 1 relay per prop, which I guess is fine and probably better in the end.

Can anyone recommend any relays to use for something like this? Last time I did something like this was to trigger a fog machine. I ended up using the above Radio Shack relay enclosed in a Radio Shack project box. But perhaps for something like this there's a simpler/cheaper relay I could use...

 

[WayneW]

Can anyone recommend any relays to use for something like this?

I love the RIBU1C

 

[ano]

You don't need to use one relay per prop, but you do need to use one set of contacts per prop. The relay you listed here has two sets of contacts. You can find other relays with more contacts, but Radio Shack might not carry them. So a DPDT stands for Double Pole Double Throw, Double meaning two, so there are two sets of contacts and each has two positions. So a SPDT relay would have one (Single) set of contacts.

Look for something like a 8PDT relay. That would have eight sets of contacts and potentially control eight props.

 

[stusviews]

You would need only a single-throw (ST) relay, for example, SPST is single-pole single-throw, 8PST is 8 poles (connections) single-throw. A single-throw relay is ON or OFF. Double-throw relays have one set of contacts ON when the relay is energized and the other set of contacts ON when the relay is not energized.

But the best suggestion was to bypass the motion sensors and use just one control.

 

[apostolakisl]

If the props are activated by a dry contact switch you should be able to activate all of them with a simple spst relay by just running the wires in parallel. If they props are actually powered through the contacts in question you would need separate relay contacts for each voltage. It just depends on how the activation wires comming off the prop go about activating the prop.