Problems in cold weather

[gneirynck]

So I used a Prop-1 Controller to build some animated Christmas light controllers for my uncle up in the Midwest.  It's a pretty basic design.  I just ran the outputs to some solid-state relays to turn lights on and off according to the program.  The boxes worked great until the temperature dropped below 35 degrees.  Then one of the units quit working.  As soon as the temperature went back up, it started working again.  There are really only 3 components in the box, the controller, the power supply (12v brick with a plug in power cord), and the SS relays.  I eliminated the relays since the entire unit quits working and not just a single strand of light.  Unfortunately I'm in Texas and I don't have access to the units anymore so I have to troubleshoot them over the phone.  I'm leaning toward the power supply, but I thought I would send a message out to see if anyone else has had a similar issue.  Any ideas?

[menehune]

Can the tester see any power lights on the prop at 2am when the temp drops to 35F?  I believe most electronics are designed to be used at room temperature (50F-100F).  Temperatures outside that range can cause weird things to happen.  If the power LED is off, the external power supply is probably the culprit. 
The Prop-1 docs state typical operating temperature range is 25C-85C (77F to 185F) with an absolute minimum temperature of -40C (-40F).  I would try to keep the prop as close to the "typical" operation temps as possible. 
The Crydom D2W203F SSR claim to operate in -30C-80C (-22F-176F) temperatures.
I could not find a spec sheet on the EFX site for their power supply, but the first "wall wart" I found on the web had an operating temp range of 0C-40C (32F-104F).

If possible, I would keep all the electronics inside the house (or even in an unheated garage) and run weather resistant AC extension cords out to the lights.

If the controller must be kept outside, you could try enclosing it in a small cooler and possibly running a separate power supply outside to heat a wire wound resistor.  The resistor will act like a small space heater to keep the electronics warm.  Add a thermostat to keep a regulated temperature.  The heater power supply can be inside the house on a timer so it only turns on at night.

Davis Weather instruments has a rain gauge heater #7720 that may work.  The heater is designed to melt snow and ice on a outside rain gauge so it may overheat the stamp.  Be sure to weather seal your enclosure very well because water and electricity do not mix well.  If you are using the prop outside in ice/snow conditions, assume the melted water will get inside the box and plan accordingly.

[JonnyMac]

Are these in an enclosed box?  It would seem to me that if they were enclosed the heat generated by the power supply would be enough to keep everything warm.  The Prop-1 is designed to run well below zero so I don't think it's the culprit, unless there has been some serious thermal stress the the board that self-corrects as the board warms.

[gneirynck]

Well I managed to get some more information on the problems I'm having.  Yes, these units are in an enclosed weatherproof box.  I am getting power to the controller.  The problem unit is controlling 3 sets of lights and as the temperature drops, the light stop working one at a time.  This leads me to suspect the relays are freezing up.  These are Teledyne Solid State Relays, Model 615-8500.  However, the strange part is that the lights are not following the program when they start going out.  In other words, the third strand comes on for 2 second every 10 seconds.  Once it gets cold, the first two strands go out and the third strand may stay on constantly or blink every few seconds.  Very strange.

I doubt I will be able to do anything with it this year, but I will have to examine it at some point in the future so it will be more reliable for next year.  We even suggested putting a heating pad over the box to keep it warm.  I think I would prefer a heating strip inside the box that I could power up with the unit.  Suggestions are welcome.

[livinlowe]

Are the lights on the prop-1 blinking just like the light strands? If so it would be the prop-1. I find it hard to believe that the SSR's are failing internally, but the connection to them might be.