Keeping alarm controller warm in extreme climates?

Google on "PTC thermistor". ;-)

Best regards, Spehro Pefhany

Back in the sixties, my dad had a parking lot with an automatic gate that collected coins from customers before opening up. In cold weather, something was needed to keep the coin mechanism from freezing up.

Sure enough, there was a 100 watt light bulb in there on a thermostatic switch that kept the interior just warm enough to do the job.

True, light bulbs can burn out, but this can be mitigated by buying "extended service" lamps which have heavier filaments and consume more power/per lumen of light produced. Light bulbs have the added advantage of visually telling you that the circuit is ON.

Or you can proceed with your resistor solution. One possible problem is the end connections. You really should have some sort of protective enclosure to prevent electrical contact with a hot leads.

You might not be worrying about quite the right thing. Usually, the problem with outdoor electronics is keeping it dry in all possible climates and combinations of temperature and humidity changes. A sudden increase in temperature and humidity can leave objects (like circuit boards) below the dew point, so condensation forms on them. Condensation can collect inside the enclosure and artificially raise the humidity inside when things warm up. If the Sun then heats the enclosure, the circuit boards could be the coldest area for a while, and again be subject to condensation.

Sorry, I'm not expert in solving these issues, although I am aware of them through having programmed controllers in street furniture which sometimes include temperature monitoring and humidity monitoring at the circuit boards, so they can raise remote alarm indications if they think the circuit boards are in danger of dropping to the dew point. Heaters on the boards, enclosure ventilation and enclosure drainage are certainly one way to control the problem. However, just using heaters without knowing what you are doing could make things worse if it left the circuit boards cold in a humid enclosure.

So, can someone help me with suggestions re. how to warm them up and keep them dry?

Thanks,

What are the specs of the equipment? Most today will give you or you can find out what the btu production is. A sealed/gasketed container may be enough to trap the line power transformer heat production. You will probably want a sealed container anyway to keep out the dust. Recessing the panel into a interior wall with a tad of insulation should be enough to keep it and the batteries above freezing. The heat would be mitigated the same way because of the insulation installed about the recessed panel. Just a thought

040804 1335 - Beachcomber posted:

A 150 watt light bulb could be used with a diode in series with it. The bulb filament would not sustain such a shock when turned on and would last considerably longer, and being 150 watt, the heat output would probably be equivalent to a much smaller bulb at full voltage.

I did that once but I used two of those 40W appliance bulbs as is used in the frige. Each bulb has only half the voltage so they will last forever.

Greetings.

Not a recommendati>Need to install an alarm system in unheated/uncooled building in farm

Hard to imagine the degree of brain damage required to spec a temp range in esrever order like that....

I have used 69w signal bulb to keep things warm. Some signal bulbs last upwards of

6000hrs. They may cost a little more but it is worth it.

Hard to imagine the degree of brain damage required to spec a temp range in esrever order like that....

I'd be curious to know if the sensors also have the same temperature limit. I'm guessing, but I'd think the point of concern is freezing the back-up battery. In an enclosed box, I would think a 5W night-light bulb would keep you over 14F.

I thought that motion-sensors (PIR), if that's what you're using, actually work better the colder they get. *shrug*

John

Once asked to modify some kit for use in Arctic circle. Eventual simple solution was the fitting of a couple of metres of self-compensating heater cable from the Raychem company. regards john

Until the light bulb burns out...

Better would be 2 25W applience bulbs in series. Assume that 1 such bulb draws 0.2A @ 120V (24W) [Note 1]

2 in series will each draw 0.1A @ 60V (6W ea, 12W total) [Note 1] and will last nearly forever.

Note 1: The above makes the assumption that a light bulb is a linear resistance, while real-world light bulb have lower resistance when they are cold, but the above is close enough.

How about very hot days? Will the box get very hot from the sun and then have the bulbs make it even hotter? Does it generate enough heat under ordinary operation to require a vented enclosure?

Probably -10°C ~ +50°C

Best regards, Spehro Pefhany