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Props and the cold of NH — Parallax Forums

Props and the cold of NH

RavenkallenRavenkallen Posts: 1,057
edited 2010-11-20 22:56 in Propeller 1
After i move in to the new place i am going to set up my lab in a more permanent way. I have always wanted to make a cool weather station(Using a Prop of course).

Then i remembered something.. Oh, yeah. How would a Prop and its peripheral components handle the often bitter New Hampshire winters. The temperature can drop below 20 or 30 below here easily. I looked through the Prop datasheet and it had info about the Prop functioning fine with the internal oscillator at some temperatures, but i couldn't really glean that much from it. So, what is the lowest temp that the Prop can handle? Also, would the electrolytic filtering capacitors/ Batteries freeze up first? I have heard that they can't handle extreme cold...Should i consider making some sort of "house" for the Prop that has heating? Maybe like a greenhouse or something like that? Perhaps even throw on a couple of solar cells for power/ heat? Any suggestions are appreciated

Comments

  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2010-11-20 13:39
    As to your tag line - Not for the Father Chrismas job, I have that.
  • LeonLeon Posts: 7,620
    edited 2010-11-20 13:42
    Temperature range is in the data sheet. Other components and batteries will need to be carefully selected.
  • Mike GreenMike Green Posts: 23,045
    edited 2010-11-20 13:47
    The datasheet gives the definitive information on temperature and the Prop. As you surmise, the electrolytic capacitors and batteries will be the first to stop working properly. Check the datasheets for the specific parts involved and you'll see a temperature range for proper operation.

    A greenhouse isn't going to work well at night unless it's specifically designed for heat storage and extremely well insulated. If you're going to have the insulation, the electronics itself may furnish enough heat. If you're running everything off batteries, you're not going to be able to afford to produce heat from battery power. Usually then you're trying to make the batteries last longer by minimizing the amount of battery power used to produce "waste" heat.
  • RavenkallenRavenkallen Posts: 1,057
    edited 2010-11-20 14:47
    So upon re-looking at the data sheet, it looks like the Prop is capable of operation beyond the military specifications... So i guess the Prop will be fine. I will have to look at the other components. It appears that NI CAD batteries can go down to -40C. That should be low enough for the intended application, but what kind of capacitor can supply the high capacity of an electrolytic and have a good temperature range? Should i go with pricey tantalum? The specs say that most are capable of temps down to -55C.
  • Mike GreenMike Green Posts: 23,045
    edited 2010-11-20 15:15
    You'll have to make those decisions. You may be able to find military range aluminum electrolytics. Whether they're cheaper and smaller than ordinary tantalums with the same range is something you'll have to research.

    Keep in mind that NiCads, although they may operate down to -40C, have a reduced capacity at those temperatures. Read the datasheets carefully.
  • Dr_AculaDr_Acula Posts: 5,484
    edited 2010-11-20 16:18
    Have you got a small foam container or similar? If the propeller and batteries are in a container that does not lose heat much, the small amount of heat coming off the propeller and regulator should keep everything else warm. Lots of possibilities with insulation - bubble, wrap, expanding spray foam, even wrapping the whole thing up in a wooly sweater. Minus 30 sounds coooold!
  • RavenkallenRavenkallen Posts: 1,057
    edited 2010-11-20 16:20
    @Mike... Wow, i just checked Mouser and tantalum caps are EXPENSIVE!!! A 1000uF 6V cap is like 20-30 dollars. I will have to look into the extended range electrolytic capacitors. Those temperatures in NH are not everyday in the winter, but they do happen occasionally. I guess if the temperature gets that low i could always take the unit inside... What kind of battery/ power source would you use if you were going to take on such a project?
  • RavenkallenRavenkallen Posts: 1,057
    edited 2010-11-20 16:26
    @Dr_Acula.... Good idea. I could probably rig something like that up.
  • Dr_AculaDr_Acula Posts: 5,484
    edited 2010-11-20 16:57
    I was thinking of the high altitude balloon experiments - they usually keep the batteries and the micro/video recorder in a foam box. A foam box will work out cheaper than an expensive tantalum.
  • RavenkallenRavenkallen Posts: 1,057
    edited 2010-11-20 21:40
    @Dr_acula... Do you mean like normal Styrofoam?
  • edited 2010-11-20 21:49
    Why not just add a small heating element to your container that houses your electronics as long as you can do it safely?
  • LeonLeon Posts: 7,620
    edited 2010-11-20 21:52
    That's the stuff. It's a very good insulator.

    If you want the unit to work reliably at -30C, you really need to use expensive industrial grade parts (-40C to 85C).
  • RavenkallenRavenkallen Posts: 1,057
    edited 2010-11-20 22:07
    So i guess i should get some Styrofoam. At least it will no be hard to find, haha
    Oh and when i said 20 or 30 below i meant Fahrenheit, not Celsius...Chuck, i am wanting to power the device off of a battery of some sort. A heating element would suck up to much power(unless i could really insulate the container)..
  • edited 2010-11-20 22:18
    So i guess i should get some Styrofoam. At least it will no be hard to find, haha
    Oh and when i said 20 or 30 below i meant Fahrenheit, not Celsius...Chuck, i am wanting to power the device off of a battery of some sort. A heating element would suck up to much power(unless i could really insulate the container)..

    Maybe a small lightbulb would generate heat but it would also use electric.

    I've heard of people using a blanket over top of their car engines in the winter. I suppose it is insulation.

    I've also heard of people using bubble wrap for their windows in the winter. It keeps a layer of warm air as a barrier.

    Anyone know of any chips that generate heat?

    I would probably look for styrofoam boxes.
  • potatoheadpotatohead Posts: 10,195
    edited 2010-11-20 22:24
    What about some element, and a temp sensor? That, coupled with the styrofoam, could be pretty efficient and hardy.
  • LeonLeon Posts: 7,620
    edited 2010-11-20 22:24
    I wondered about NH getting down to -30C! Even at 30F below you still need industrial grade parts, of course.
  • edited 2010-11-20 22:27
    potatohead wrote: »
    What about some element, and a temp sensor? That, coupled with the styrofoam, could be pretty efficient and hardy.

    A heating element could be on its own circuit.
  • Dr_AculaDr_Acula Posts: 5,484
    edited 2010-11-20 22:33
    Styrofoam would work. Lots of options. A drinks cooler?

    You could do an experiment - put a thermometer and a resistor in the box and measure the temp when the box is sealed up. Set it up to make 1W of heat and see what the temp goes to. A one ohm resistor (maybe a 5W one) on a nicad will produce about 1W for a couple of hours (V=IR, V=1.2V, R=1) Approx 1800 to 2200 mAh. Or use a plugpack and work out the right resistor V=IR and W=IV.

    You might find that the propeller produces enough heat itself.
  • edited 2010-11-20 22:35
    Wood is a good insulator of heat. Paper is also an insulator.
  • edited 2010-11-20 22:43
  • edited 2010-11-20 22:56
    I was looking online and you can get flexwatt heat tape. It must be used with a thermostat or rheostat:

    http://www.reptilebasics.com/flexwatt-heat-tape/

    Aluminum foil tape can take a lot of heat and fasten down heating elements:

    http://www.reptilebasics.com/aluminum-foil-tape.html

    They sell heating pads for reptiles so it could keep electronics warm.
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