Ren-W Controller Heater

Ren-W Controller Heater

In some very cold situations (below freezing), you may encounter a problem whereby a controller may function fine above freezing, but when the temperature drops below freezing, or even below zero, the controller ceases to respond. The problem is that either the Ren-W cannot "lock in" and capture a signal, which of course creates a communication problem or the temperature is outside the manufacturer's specs for proper operation. For example, the XBee radio is rated to -40C, which is pretty cold. But the MAX232 chip that Ren-W uses comes in multiple kinds, and the operating temperature specifications can vary widely. If the MAX232 ceases to function, communication to the controller cannot occur.

Likewise, it's possible that components on the controller itself may cease to function when the environment is outside the operating temperatures of the components. The chips that control RS-485 communication, or the H11AA1 optocoupler, or perhaps even a PIC might not like very cold temperatures.

The solution is simple: install a small heater bulb inside the controller box. The steps below outline one solution that is proven to work.

Parts and Tools Needed

• Candelabra socket with a mounting hicket/lug. Example: Servalite CS-10014-52U. (Lowe's, about $2.75)
• 15watt, 120vac tubular light bulb with candelabra mount. (Lowe's, 2 for approx $3.00) These are quite small, about 2" long and 1/2 inch across.
• Length of SPT-1 or SPT-2 cord
• A/C plug
• Zip ties, possibly heat shrink tubing or wire nuts
• 1/4-20 x 1" long screw, nut and 3 appropriately sized washers
• TOOLS: drill, screwdriver, pliers