[MattMacLean]

I've seen several threads on "Similar items" but none that covers this one so I desperately need help.

So, what I'm trying to do is to have a single sound play when when electricity is hooked up to the device. I have a motion sensor rigged to an extention cord, so when it detects motion, everything thing that is plugged in will activate.

I bought one of these:
http://www.electronics123.net/amazon/pictures/br9.jpg

I plan on cutting off the battery snap and attaching a 9V adapter which I already have. I also plan on taking off the speaker and mic and replacing them with a headphone and a microphone jack so that I may use decent speakers and a decent microphone.

The part I need help with is, how do I make it so when the unit recieves power it will play the sound instead of having to press the play button. I'm sure some of you have already done something like this so I would greatly appreciate your help and guidance.

Thanks,

MattMacLean.

 

[Jack Skellington]

You need something that will simulate the Play button being pressed.

I would use a 110 VAC relay which would be plugged into your extension cord. Cut the wires to the play button and connect them to the NO relay leads. When the relay is powered the leads will close which simulates the play button being pressed. Leave the 9V battery leads and just connect them to a battery so the unit is always powered.

 

[MattMacLean]

This may be a stupid question, but what is a relay. I'm useless when it comes to this stuff. Unfortunately.

 

[MattMacLean]

Or is there any way to do it without a relay?

 

[Jack Skellington]

Think of a relay as a switch that's triggered when you apply current. The 110 VAC relay I'm talking about is powered by an electro magnet. When you power the relay it flips from one position to another. It has 2 types of terminals NO (normally open) and NC (normally closed). The NO terminals are closed when the relay is powered so it can be used to simulate the pressing of a play button.

Here's a relay that I commonly use for my props when I need to trigger multiple things such as audio players.

http://www.allelectronics.com/make-a-store/item/RLY-453/120-VAC-RELAY-DPDT-12-AMPS/1.html



I put them inside some type of enclosure, usually a plastic electrical box especially when working with AC current.

 

[MattMacLean]

Okay, that seems easy enough. So I'd wire the source of the electrical current (positive and negative/neutral) to the NO, and wire (positive and negative/neutral) of the audio player to the NC?

 

[Jack Skellington]

No, you wire the source of the current to the coil terminals of the relay. These are what power the electro magnet and cause the relay to switch on and off. The power connects to the 2 terminals that are perpendicular to the other six terminals.

Then you wire the play button to the NO terminals of the relay. This particular relay has 2 NO terminals so you can use either set. For the one pictured they are the next 2 terminals on either side. This is a DP (Dual Pole) relay so you could trigger multiple players if you had the need or any other type of device that needs a switch.

Powering one would be a first good step so you could see how the contacts switch on and off.

Understanding and using relays makes haunting so much more fun IMO.

 

[MattMacLean]

Ok so this may be a stupid question, but I'm afraid of shorting or blowing something.

I will have the 9V adapter hooked to the power, that's a given.
Will I also need to wire the same 9v adapter to the Relay then to the play button? Or would I need another 9V adapter or does the relay need 120V? Also, would it be better to have the little circut board on constantly and just have it triger the play button? Or have it turn on when I need it to?

Also do I need a special type of relay or will any relay work?

Just to claify what I'm trying to get my prop to do:

I made a motion activated extention cord, so that whenever motion is picked up anything pluged in will start. As of right now I have a flood light, and a pneumatic "contraption" that I built, both of which work. So I also need the sound which will be plugged into the same extention cord.

Sorry for all the questions, and I REALLY appreciate your help.

 

[Jack Skellington]

There are no dumb questions when working with electricity.

The 9 volt adapter will not be connected to the relay, it should be connected separately and powered continuously. The audio player will be sitting there waiting for the play button to be pressed. In order to do this it needs to be powered up already.

The power to the relay will be plugged into your extension cord along with you others props that will be powered on when your motion sensor triggers. The power coming on will cause the relay to "flip" to it's powered position. This will cause the terminals that are open to close. Connecting the play button wires is the same as if someone pressed the play button manually.

Since you're going to trigger from your AC power you need a relay that's rated for 120VAC. The one I posted the link to will work quite well.

You could add another circuit board but then you're just adding another layer of complexity.

Here's a simple connection picture

 

[MattMacLean]

Wow thank you, that was very informative. I thought of another question. Where te relay is tater 120VAC does that mean it will deliver the full 120v to the play button? I'm just thinking, since the board is meant to be powered by 9v and it does deliver the full 120v that wouldn't be very good would it?

 

[Jack Skellington]

The relay won't supply any current to the play button at all. Where the play button is connected is just a "dry" contact switch. The mechanical relay contacts are an isolated circuit.

The 120VAC only powers the relay coil to cause the contacts to close.

 

[MattMacLean]

Ah, okay, I understand what a relay is now. I feel slightly stupid for not understanding it in the first place. Thank you very much for your help. When I get the parts in the mail I shall let you know how it goes. Any tips on where to pick up a relay locally? I'm in Canada and Im not sure what type of stores would sell them.

 

[Jack Skellington]

I get mine from a local electronics store or online. They're usually cheaper online. I bought a bunch on e-Bay a couple of years ago.

One more picture of the internal guts just so it's all clear. I know you understand but I had already mocked up this picture.