Robot having internal heat problem

[Gene]

Originally Posted by KenWittlief

Im not aware of any special cooling being used on electronics in the desert in Iraq.

Motors can get very hot with no problems. Most commercial electronic devices are rated up to 95C (not F, C).

The fact that its 100F in Arizona is no big deal. How hot do you think it gets under the hood of your car in the summer? How about inside your car after its sat in the sun all day? CD player still works just fine pumping out 500W inside a car that is hot enough to kill a dog.

Ambient air should be all you need, even in the desert - you just need to open the case a little and let the outside air in.

The M1As use internal air conditioners to keep the temperature below 95 F. because the fire control systems are all electronic. Please don't ask me for more information about the details of these systems.

iRobot also warns military end-users of potential heat related problems associated with desert operation.

Aircraft avionics in addition to the weapon control systems are equipped with some very expensive cooling devices to include tubes, plates AND Peltiers.

Added:
Here is a overview of Peltiers: http://www.dansdata.com/peltprac.htm
The operative phrase is high amps. As he mentions, the efficiency is increased as the load is increased. For the small ammo-bot, I think they may be the kiss-of-death because of battery requirements. But then, I'm only a ME not a EE.

[Andrew Blair]

Originally Posted by lukevanoort

Unfortunately, that'll only get it down to ambient temperature unless you use an active cooling method. For that, you need some sort of refrigeration, most units are much too heavy/power hungry, the only thing that I can think of that could do it is a Peltier junction. These are nifty little ceramic (I think) blocks that get hot on one side, cold on the other when you run current through them. Then you have to worry about condensation. Peltiers could instead be used with fans to help reduce the temperature below ambient. I don't know where you could get one though, but they used to be popular with the extreme case-mod/water-cooling crowd so there probably is a place to acquire them. Most will probably be in the 12VDC area, but power consumption is pretty low, (if I remember correctly) 10 NiCd AAAs could probably power it and the robot, NiMHs would be even better. (less toxic) The Robot Marketplace has customizable battery packs you could use.

Ooohh...Peltier's...those are cool. I might just suggest this little baby- http://www.electronickits.com/kit/co...tier/ck500.htm

You seem very intent on cooling the air, not just introducing it, so this in a sealed metal box would work quite nicely. Otherwise, just use a plain fan and some bullet holes as Bilbo said.

But I have a question: What kind of kid goes outside in 100 degree temperatures to play with a robot instead of slugging around inside watching TV? Sounds more like some crazed ME to me... ;-)

[Gene]

Originally Posted by Andrew Blair

Ooohh...Peltier's...those are cool. I might just suggest this little baby- http://www.electronickits.com/kit/co...tier/ck500.htm

But I have a question: What kind of kid goes outside in 100 degree temperatures to play with a robot instead of slugging around inside watching TV? Sounds more like some crazed ME to me... ;-)

Outside air would be nice - if it was cooler.

I'm guilty. He and his friends were talking about science projects, the news on TV (Iraq) and neat stuff like iRobot's little devices. So I thought a little robot would be a wonderful learning experience. . . and - well . . . . . it has been.

He rarely watches TV.

[lukevanoort]

Y'know, speaking of spending time inside, couldn't he drive the robot inside?

[Kevin Sevcik]

First, I thought MEs were all about heat transfer. I know I had to learn entirely too much about it in college.

At any rate, I'll add to the chorus. I really think ambient air is your best bet, since anything else requires expending relatively large amounts of (electrical) work in order to cool below ambient. Simple thermodynamics and all that.

Thinking about it, you could just make a rechargable cooling unit, however. Just something you put a piece of dry ice in and it provides enough cooling to last for a few hours. If we could get an estimate on how much current the whole ammo-bot draws we can figure out how much dry ice you'd need. In fact, an estimate of the power draw would be useful for figuring out any cooling solution.

So... basically, what size batteries are we talking about, and how quickly do they get drained?

[KenWittlief]

whats wrong with wet ice? (besides being free from the ice cube maker? :^)

[Kevin Sevcik]

Originally Posted by KenWittlief

whats wrong with wet ice? (besides being free from the ice cube maker? :^)

You'd have to work up som system to get the cold to the electronics and pipe the wet water somewhere away from them. Though I did consider it. I was first thinking of some liquid you could evaporate, Which neatly solves the condensation problem you're likely to have with either wet or dry ice.

[KenWittlief]

or put ice cubes in a small freezer bag

[Gene]

I’d like to thank:

Al Skierkiewicz
Andrew Blair
billbo911
Billfred
KenWittlief
Kevin Sevcik
lukevanoort
NoodleKnight
sanddrag

for all the help, thoughts and concerns provided by a great bunch of guys.

I let the “little fellow” review the thread, then we had a Q and A.

One of the more pronounced issues you guys helped him learn and perhaps one of life’s most important lessons, is that everything has trade-offs. And just as important . . . design and build for an application.

His solution, redesign. Use different more nonconductive outer materials, good insulation, incorporate a larger power source, draw external air until it reaches a predetermined temperature, then to use Peltiers with thermocouples to avoid a constant power drain.

But the big deal, at least to me, is the team concept and importance of listening to everyone’s input . . . because moving “in the opposite direction” may be the wisest decision.

[Al Skierkiewicz]

Anytime, just ask. Good luck! 73's