Posted by - Sleepy Coote on March 06, 2003 at 08:23:54:

In Reply to: Re: power outages posted by Frank Black on March 06, 2003 at 07:02:17:

It's been a while since I built it. I *think* I selected a 75dB piezo electric buzzer that operates on DC voltages between 1.5 and 3.0 volts. That 75dB buzzer sitting on my night stand is loud enough to wake me without any problem. I can even hear it elsewhere in the house. It's important to match the buzzer's DC voltage rating to the load voltage delivered across the light bulb--which is where you will wire/solder the buzzer in parallel. There was enough free space inside the Intermatic emergency light to nicely hot-glue that buzzer. I drilled an appropriate hole in the emergency light's front case to properly conduct the alarm's audio outwards.

I bought a 1250 VA Smart UPS used and placed brand new batteries in it. Then I hooked it up under load for several days to a digital storage scope to make sure the 60 Hz AC output was safely within tolerance. If I didn't happen to have a piece of test equipment to verify the used UPS, I think I would have bit the bullet for a couple hundred more dollars and bought a brand new UPS that also puts out a pure sine wave. Others have saved money on their UPS by buying the less expensive one that puts out a squared off or "approximated sine wave"---then making it a point to power the CPAP but *NOT* the heated humidifier with it. I think F&P puts out the only heated humidifier that can cope with a squared off AC input waveform.

With that said I placed the UPS in the next room so I wouldn't have to hear any UPS beeping when it kicks in for a power outage, brown out, or even slight under-voltage. Alternately I could have electronically disabled the speaker in the UPS. A long very thick extension cord runs discretely from the home office hosting my UPS to our bedroom, where the CPAP sits on my night stand.

I also mounted a two-outlet AC receptacle in a double gang box. The other position in that double gang-box contains a 60-minute rotary AC timer switch. That rotary timer switch controls one of the two neighboring AC receptacles. I use it for blow drying my CPAP hose on a timer with automatic shut off (that way I can leave the house after starting the hose drying process). The other AC receptacle is always on, and powers my AutoPAP continuously throughout the night. The emergency light-buzzer plugs into that always-on receptacle, and the AutoPAP plugs directly into the AC receptacle built onto the front of the emergency buzzer-light.

The double gang box is mounted in a metal project box, with case continuity to AC ground. That box in turn has a heavy AC cord coming out of it, which plugs into the UPS's very long extenstion cord. All parts are off-the-shelf, requiring only basic wiring and soldering skills, and the final project is not at all aesthetically unappealing (my wife's biggest initial concern!).

Hope this helps!

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