I have a semi-low-tech idea for you: Something like the following, potted in some hot glue with a magnet stuck on the side of each unit.... http://www.instructables.com/id/The-Ultimate-FM-Transmitter/ You could also waterproof with a ziploc bag, etc. These are available in various forms, kits, finished, etc.... I'd probably design such that the microphone element is against the metal of the unit. On Thu, Jun 1, 2017 at 4:10 PM, Neil wrote: > Hi all, > > My neighbor and I are trying to find the source of a noise that's > bugging us, which is from one of 6 A/C units on the roof above us. It's > a periodic hum, plus a noticeable rattle when the thermostat switches > off that unit. I've asked the A/C service guy to check and he says it > would take quite some time to monitor for that. > > I know it's not my A/C unit as the hum/rattle does not coincide with the > operation of my A/C. Same for my neighbor. One of the other possible > residents is gone for 11+ months each year, and I doubt he'd leave that > unit on all year. So that leaves 3 units. Coordinating with the other > residents has been difficult, so I'm thinking I can come up with some > sensing device that can remotely alert me as to which unit is switching > on/off at any time. The other complication is that I am not allowed to > be on the roof (insured A/C repair persons only), but I can just > probably just deploy the sensor with a drone perhaps. > > So... what's an easy way to sense this? Getting a current sensor around > the A/C lines will be difficult, but a vibration sensor magnetically > attached to the side of the unit should be simple. I'd think I can > create a small circuit with an accelerometer and a processor (perhaps an > Arduino), then add some type of wireless transmitter, and a power > source. BTW, power really only needs to last a few days. And then > there's enclosing/waterproofing. > > Alternately, I'm wondering if I can mount a wireless camera up there > facing all 6 units and vertically attach a stick to the side of each > unit and see which one rattles when the A/C goes off. Assuming the > rattle is enough to visually move the stick. I'm fine with low-tech. > Any other ideas. > > I really don't have a lot of time for custom circuitry right now. There > has to be a simpler way. Is there some pre-made device I can use to do > this, or most of this? > > Cheers, > -Neil. > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 *Forrest Christian* *CEO**, PacketFlux Technologies, Inc.* Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 forrestc@imach.com | http://www.packetflux.com --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .