[halcyonforever]

yeah that would be correct. A diode is placed “backwards” across the load side of the relay to prevent voltage spikes. I normally am using the relay to control AC on/off which gets voltage spikes anway so I don’t normally think to include that.

[halcyonforever]

well, the 12v device won’t run directly in line because the system has at most 9v power.

What I would use is something like
http://search.digikey.com/us/en/products/SSRT-240D10/PB553-ND/678187

they are expensive but I have several that I have scavenged out of various broken machines. So what you are looking for is something with an operating voltage with a low end below 9. And the load voltage higher than what ever you want to plug in. These ones will let you turn on your coffee pot, so they are overkill I just use them for various automation ideas.

You mentioned a diode, were you trying to setup a protection diode for the load circuit?

[halcyonforever]

arrived today! verified parts count and dry assembled. will start soldering tomorrow.

[halcyonforever]

the way I would do that would be to connect the buzzer leads to a suitable relay that triggers the other device.

That’s the major change I intend to make, by capturing that output you can make anything happen.

[halcyonforever]

Order placed! Can’t wait to build it and film it!

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