Speaker driven relay to dry contacts (newb)

Thread Starter

bzn

Joined Nov 23, 2016
4
Have mercy on me, I'm not an electronics guy, but I am very comfortable with simple circuits. Total newb to most electronics terms, however I am somewhat familiar with some.

So here's the project:
I have a driveway alarm (Mighty Mule) that works very well. It has a small receiver with a little PCB speaker that plays several notes for a couple of seconds when triggered.
I'd like to hack it to drive a relay from this to the dry contacts of a z-wave door sensor. When the alarm goes off, the door sensor closes the dry contacts and the SmartThings hub turns on the driveway lights.

I measured some voltage on the speaker with a multi-meter. So I'm figuring I can tap this to a relay or something to close the contacts while it's playing it's "doorbell" tone. I want to keep the speaker announcing, just add some automation to the event.

Can I use a low voltage relay? That is simple enough for me to understand. If so, what kind. Solid state? Reed?
Or do I need to have some other circuit device.
 

Dodgydave

Joined Jun 22, 2012
8,807
If its got a speaker making a tune, it will be pulsed Dc or an Ac signal at low voltage,, so you'll need to amplify and rectify with an op amp or similar circuit it to operate the relay.

Unless it has an output on the receiver with a fixed dc signal going high or low at the same time as it plays a tune.
 

Thread Starter

bzn

Joined Nov 23, 2016
4
So in simple terms, how do I amplify and rectify with an op amp?

The receiver is simple, no external outputs, just a volume control. I measured a flash of about 1 - 1.3 volts on the speaker terminals. It's a tiny PCB speaker and I doubt there's much wattage on the thing.
 

Thread Starter

bzn

Joined Nov 23, 2016
4
The "Visitor" LED lights up when the driveway alarm is triggered and stays lit until reset. We never reset it, so it's essentially always on.
It uses a 12v power brick for power.

If I could tap that PCB speaker and amplify it enough to trigger a relay, that relay could then close the contacts on my z-wave door sensor which would trigger an event to turn on the outside lights.





 

Dodgydave

Joined Jun 22, 2012
8,807
Looks like the manufacturer has removed the numbers on the chips, also the speaker is a piezo buzzer, it will be given an ac signal by the chip possibly by Q1, you need to measure the voltage on the piezo buzzer.
 

Thread Starter

bzn

Joined Nov 23, 2016
4
I stole that image from the Internet. My receiver is not a piezo buzzer as shown in that photo. It's a speaker and plays a tune. Dee-doo-da-dee.

So doing some testing on the Zwave door sensor appears that it simply needs to sense resistance. I think they use the same device for moisture sensors because if I hold both leads in my fingers tightly, it senses a closed contact. So they must be connecting this to a magnetic switch for the door sensor.

Sooooo...I'm thinking maybe I don't need a relay. I just need a circuit that will close the contacts on my zwave sensor.

Just to reiterate. When my driveway alarm speaker sounds, I want the contacts on my zwave sensor to close. Pretty simple.

Remember, I do fine with electrical circuits, but electronic circuits are a challenge. Google came up with an idea to use a transistor.
Can I do something like this? The key is that the zwave contacts must be completely open until the speaker goes off.

upload_2016-12-19_17-21-55.png
 

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Jkjeep2010

Joined Sep 11, 2017
1
I stole that image from the Internet. My receiver is not a piezo buzzer as shown in that photo. It's a speaker and plays a tune. Dee-doo-da-dee.

So doing some testing on the Zwave door sensor appears that it simply needs to sense resistance. I think they use the same device for moisture sensors because if I hold both leads in my fingers tightly, it senses a closed contact. So they must be connecting this to a magnetic switch for the door sensor.

Sooooo...I'm thinking maybe I don't need a relay. I just need a circuit that will close the contacts on my zwave sensor.

Just to reiterate. When my driveway alarm speaker sounds, I want the contacts on my zwave sensor to close. Pretty simple.

Remember, I do fine with electrical circuits, but electronic circuits are a challenge. Google came up with an idea to use a transistor.
Can I do something like this? The key is that the zwave contacts must be completely open until the speaker goes off.

View attachment 117191

Did you ever find a solution for your mighty mule driveway sensor?. Im in the same boat right now trying to figure a way to add a dry contact to the piezo speaker. {same as pictured above} I read 1-1.3 volts ac when it triggers. I thought about using a 5v 12v 24v dc sound sensor light control relay switch module adjustable delay t1. If anyone has any suggestions I would appreciate it.
 

philba

Joined Aug 17, 2017
960
If I were hacking the device, I'd use the visitor LED. Just route it through an opto isolator to essentially create a dry contact (though it may be simpler than that). I'd also set up an auto reset of the system after a certain amount of time has elapsed to turn off the visitor LED (and maybe the driveway lights too).
 
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