Near Intersection of I-35 & I-90 Southern Mn. | Very interesting. I don't really have need for the dryer monitoring since our dryer setup is located on at my brother's dooryard but I'm always curious. I can think of some other situations where this might be very useful.
I would think the repeat feature would be desirable to insure that "someone actually hears" the message.
Ron - my thought on wiring this would be to use a relay that has both a Normally Open and a Normally Closed terminal as well as the Common terminal. The battery would be wired through the Normally Closed and Common terminals. The coil would be connected to the dryer.
When the dryer is running and everything is fine, there would be power to the coil which would hold the points to the Normally Closed terminal open. When the dryer stops running, the points in the relay would close (due to the internal spring) and send battery power to the radio and set it off.
This reminds me of an alarm system I built this weekend for my pressure washer in the shop. I have a manual slide gate that allows the heat from the pressure washer burner to vent to the outside world.
There are two situations that I am concerned about 1) forgetting to open the slide gate when using the burner and 2) forgetting to close the slide gate after I'm done. Leaving the gate open in the Winter is a great loss of heat and could cause the washer to freeze (this has happened at work).
I built an alarm box that does a couple of things: 1) interupts the burner circuit unless the slide gate is fully open and contacts an implement switch 2) Sounds an alarm when the switch is deflected. My idea was that 1) the burner would not start unless the operator did in fact open the slide gate and 2) would be reminded to shut the gate when finished due to the alarm sound.
The alarm would be sounding while actually using the pressure washer with the burner ON but I felt that the noise of the washer would mask the alarm and it would not be too irritating.
It turns out that my "backup alarm" was too loud and was irritating during the time of legitimate operation. I hit upon the idea of modifying my alarm with another relay so that the noise would stop as long as the pressure washer burner was actually ON but that the sound would start as soon as the operator turned the burner OFF but the slide gate was still open. I also changed the alarm from a backup type to a doorbell chime type (less irritating).
This was a good idea but didn't work for me. The reason being that the pressure washer is wired pretty much with 240 Volt A.C. The indicator lights and rotary switch all seem to be 240 volt. My 110 volt relay for the alarm needed a neutral which I could not find inside the pressure washer. My only choice was to connect to the AC ground. This would have been OK but the pressure washer is equipped with a GFI in the power line.
Once the pressure washer was set to turn ON the burner, the GFI tripped since it noticed a load to ground. My only choice was to disconnect the ground so the chime alarm sounds whenever the slide gate is open. My only net improvement on my modification is that the chime is quieter and is not as much of a nuisance while actually using the pressure washer but does provide the warning when the washer is OFF.
Edited by tedbear 12/31/2008 02:46
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tedbear Thread from below
