I need to make a freezer alarm. have 3 full freezers that are for fish bait.
the sensors and such are not a problem, but I have not used any sort of annunciation.
the warehouse is one wall away from an office and there is foot traffic a couple times a day.
It will have full power, no batteries.
any suggestions as to what to use to draw attention ?
dave-in-nj:
I need to make a freezer alarm.
What conditions? Power failure? Over temperature? Under temperature? Humidity / ice formation?
any suggestions as to what to use to draw attention ?
What sort of attention? Get here NOW? Check when convenient?
Who's attention? A store clerk? You? Someone who may not be onsite?
there is foot traffic a couple times a day
Which precludes anything especially loud (hearing damage).
freezer alarm if the temperature gets too warm.
the alarm will beep/buzz/click/clack... to draw attention, probably for 5 minute upon failure.
then a few seconds every minute.
looking for something 5v, annoying enough to get some attention, no so loud as to damage one's hearing.
ideally in a case, or mountable in a case with the rest of the project.
DS18B20, flat ribbon cable to allow it to fit in the seal of the door.
I've tested about two dozen low voltage beepers. This is, by far, the best one I've found...
https://www.google.com/search?q=CPE-164
Run it at it's resonant frequency. I believe that's 4 kHz but check the datasheet. If possible the beeper opening should be open to the room pointed straight up.
If I remember or you post a reminder, I will check the duration I used. I believe I went with 250 ms out of every 1 second.
I epoxy the beeper flush to the case aligned with a slightly larger hole drilled in the case. Roughing the top of the beeper with a file gives the epoxy excellent adhesion.
The polarity matters. You will get more volume when it is correct.
The beeper was too loud with this library...
https://forum.arduino.cc/index.php?topic=142097.0
But you may want something louder for what you're doing.
Or, you could modify that library to give an optional volume boost if the alarm condition endures.
I recall seeing on the internet a transistor / capacitor circuit that makes piezoelectric beepers much louder. If you're interested, I will try to find that circuit.