Modify a 6 EUR smoke detector for use with microcontroller, auto-dialer, linking, and more

Step 6: Reassembly

To run the extra signal and ground wire, I cut a small square notch from the lip of the base plastic piece and secured it with hot melt glue, after zip-tying the two wires together.  Hot glue was reapplied to secure the battery clip.

And that's it!  You now have a battery powered smoke sensor for your next home automation, science project, or DIY security system!

Comments

[unclebuckbike]

In am wondering if it is possible to wire a standard smoke alarm to a speaker/buzzer of a lower frequency. It is typical for people loosing their hearing to loose the high frequency first. For instance I cannot hear anything above 3000hz and very poor below that. If I could have a smoke detector below 2000hz I might hear it. As it is I can stand right under a ringing smoke alarm that is driving everyone else nuts and I don't hear it at all. The manufacturers make hearing impaired smoke detectors that are louder...blink a light or talk to you. but this is not going to wake me up if it goes at night. Can you provide any insight into this?
Thanks in advance.

[redxine]

Absolutely! It is simply a matter of modifying a detector with any of the chips listed in step 4 as per above and connecting the buzzer. However, since lower frequency buzzers will more than likely draw more than 100 mA, you may need a transistor or FET to switch the buzzer. I've attached a schematic for simple switching with a transistor or relay below. Be sure that the working voltage for the buzzer is close to 9V, otherwise an additional battery or external supply will be needed.

I will be adding this and more to a going farther step later, in addition to what to do for detector chips without an I/O pin (as soon as I find one!). I have only tested what's here with optical detectors, as they have become much cheaper and much more common here in Europe.

I hope this helps.
Edit:  didn't realize how instructables would resize the image.  Schematic is here:  http://jkltech.net/screenshot49.png