Relay question

[MrCrowley]

I've got an electronic doorbell disassembled to use for a remote ignition circuit. The receiver takes 2 AA batteries for an output of 3v. When the door bell is triggered, the circuit supplies 3v for about 3 seconds.

I need a 3v relay that will be triggered when the doorbell button is pressed, so I assume that means the relay will be normally closed. Once the relay is triggered, it will complete a circuit with a 9v battery (that leads to my stun gun circuit) until the doorbell stops producing current. The relays below are the only 3v ones I can find anywhere in NZ, is one more suitable for my application than the others? Not really sure which one to choose.

relay 1
relay 2
relay 3
relay 4
relay 5

[Mr.Tallahassee]

I think they all will work just fine. They're basically the same other than amperage ratings on the contact side.

[dewey-1]

MrC;
Is the chime similar to this;
http://heath-zenith.hcents.com/data/man ... 551-10.pdf

I used this one to remote control my X-Box several years ago.

As far as the relay selection, I would use relay 5.

[MrCrowley]

I apologise Dewey for not supplying the door bell info, should have done so in my first post. It's an Arlec DC149 and similar to the one in your link.

Product page
Spec sheet (doesn't really help)

Thanks for the advice on relay #5.

[POLAND_SPUD]

lol I hope you like the tune it plays when triggered because you're going to hear it if you connect the relay directly to the speaker output

seriously, relay will resonate and you will hear the tune...

[MrCrowley]

Really? Shit, I didn't see that covered on any forums where people have done similar mods

[POLAND_SPUD]

I've done exactly the same thing and I got this effect (even with an electric motor)

lol get a doorbell that plays the imperial march and pretent you spent a lot of time to get it to work in that way

[Fnord]

You could presumably just wire in a rectifier and smoothing cap to the output of the doorbell to reduce or eliminate the sound output.
It's kid simple, four diodes and a small electrolytic capacitor rated for ~10v is all you need. You can probably get these components from a wall-wart transformer or a broken stereo. Or half a dozen other devices.

You *might* need fast or ultra-fast recovery rated diodes, depending on the sample rate of the sound being played. I'm not really sure.

[POLAND_SPUD]

ohh well anyway I guess it doesn't matter much... since you probably won't hear it when the gun fires (due to hearing protection (yeah right) or because the boom will render you deaf for a minute or so)

[MrCrowley]

You could presumably just wire in a rectifier and smoothing cap to the output of the doorbell to reduce or eliminate the sound output.
It's kid simple, four diodes and a small electrolytic capacitor rated for ~10v is all you need. You can probably get these components from a wall-wart transformer or a broken stereo. Or half a dozen other devices

I see a guy here used a 10v 100uF cap to fix the problem, I assume I will probably have to short out the resistor as well.

[dewey-1]

MrC;
That is pretty much the same thing I did.
I see that article came out after I did my own circuit with the single tone.

[MrCrowley]

I read somewhere that transistors can be used as switches, particularly in low voltage applications. Should I stick with a relay or is there promise in using a transistor as a switch (how ever its done)?

I also noted some people use a diode to protect the transistor that amplifies the signal before a relay, is this something I should also follow?

If you guys have any other ides about a switch for this circuit, don't hold back as I'm open to other ideas. What ever is easiest is best since I'm a complete electronics novice.

[dewey-1]

The diode should be added to the coil of the relay which will protect the driver transistor from inductive voltage spikes.

I will draw of a schematic for you using relay 5.

Can you post close up pictures of the speaker transistor from top and bottom of circuit board?

[MrCrowley]

Didn't know there was a transistor/where it is on the circuit so I just took a bunch of photos that you can view here:
http://s75.photobucket.com/albums/i290/ ... 20circuit/

[dewey-1]

Here is the speaker driver transistor.