Device to remotely show IR heat lamp bulb failure via RF link?

[Chris Wilson]

I breed dogs and some live outside in kenneling. I have IR heat lamp bulbs in guarded reflectors that come on when the weather is cold at night via 2 mechanical mains timers. Two lamps are fed off one socket / timer, two from a socket / timer divorced from the first one. I wish to build a device(s) that shows filament failure that's as simple and reliable as possible, that sends an RF signal to a device in the house 30 yards away to show bulb failure. Ideas please? Thanks.

[BradC]

Wireless power meter?

[Chris Wilson]

Thanks. I can sort of see how this could work but not sure how I could trigger say an audible alarm should a bulb fail? At one point my thinking went towards a relay coil in each bulb live feed, with a pair of contacts open with the coil energised, when the contacts close the TX is energised, but the voltage drop would probably be too great. I am thinking along the lines of a mains powered mini TX for each lamp that sends a signal if the current draw is removed. The TX would be mains powered by the timer so it would be unable to TX outside the time ON periods.

[T3sl4co1l]

How about a current transformer and a long cable (can be ordinary signal level cable) back to the receiver area?  A little bias into the loop will prove if the CT and cable has failed; meanwhile, the CT measures current in the load, which, while the lamps are supposed to be on, you expect to measure exactly a proportional amount of current on the cable.

There are also current-sensing relays that work on a similar principle but have a contact closure output.

As for doing that wireless: keep in mind, an RF link is a tricky basis for something you want to be reliable.  RF is necessarily, by its nature, unreliable.  You can get something simple like a bit-bang Zigbee module or whatever, but you'll be limited by whatever error correction it has (which, read up on the system -- I don't know, myself!), and you may be better off with some sort of encoded signal to give better confidence in the received signal (or lack thereof).  So... it can very quickly go from "string up this dumb wire" to "write this complex encoder in a microcontroller", and somewhere inbetween lies the best method for you.

Tim

[Marco]

You can invert the RF signal, turn the unreliability into false positives ... which at least won't harm the dogs.

[t1d]

There are all sorts of ways to do this with a microcontroller. Arduinos are popular. Basically, you would use your choice of sensor type... infrared light, heat, regular light, power, etc. and have the MCU notify you, when the condition for notification occurs.

There are all sorts of notification signal types, for you to choose from... RF, BlueTooth, WiFi.

All of these components come in sub-assemblies, which are cheap and easy to put together. The programming for the MCU is likely available for download, too.

Google for kennel warmer circuits. Chicken warming circuits, too. There are lots of solutions, out there. Include the name, too, of the MCU type, that you choose and an exact solution will, likely, pop right up.

[Zero999]

How well thermally insulated is the kennel? 30 yards is pretty close. If it's not perfectly insulated, it should be possible to remotely monitor the temperature using an long wave IR detector and activate an alarm when it's too cold.

Another more elaborate idea, which should work with a well thermally insulated kennel but will be more challenging to build, is to look at the microwave emissions. Hot objects also produce significant emissions in the microwave range, which will pass through most materials used for thermal insulation. A directional antenna pointed at the lamp will see an increased noise temperature, compared to an object at room temperature. Of course this will only work if the kennel isn't made of metal and wet weather may also interfere with it too.
http://www.ursi.org/proceedings/procGA08/papers/A03p5.pdf
http://przyrbwn.icm.edu.pl/APP/PDF/118/a118z6p38.pdf

[brybot]

Expanding on your original requirement, why not monitor temperature directly, since fundamentally, that's what you care about. Besides a bulb burning out, your controller could also malfunciton and leave the bulbs on constantly which could potentially overheat your dogs. Remote thermometer solutions should be easy to find.