Robot having internal heat problem

[Gene]

Does anyone know of an easy way to reduce the internal temperature of a small robot - other than heat sinks and fans?

It's a small robot my son assembled and is operated by a small battery... so some of the more sophisticated energy consuming techniques won't work.

Thanking everyone in advance.
Gene

[sanddrag]

The two methods you mentioned are the most conventional. Other methods are dry ice and "canned air" turned upside down and sprayed. Be careful with the two of these things though.

[NoodleKnight]

Originally Posted by Gene

Does anyone know of an easy way to reduce the internal temperature of a small robot - other than heat sinks and fans?

It's a small robot my son assembled and is operated by a small battery... so some of the more sophisticated energy consuming techniques won't work.

Thanking everyone in advance.
Gene

Bigger heatsinks (maybe even a large brick of copper) & more fans, mainly, if you can get a proper air flow going over the hot spots then that'll pretty much fix the problem. If you can't power a fan, I suppose you could try using copper heatpipes to channel heat to a heatsink outside of the robot?
Dry ice might work. It runs out, though. And putting dry ice or turning a duster can upside down and spraying hot spots can create thermal shock, which is generally bad.

Hope this helps.

[Gene]

the little guy loves to run this thing in the middle of the afternoon - plus the exterior of the can is also used to mount the gearhead motors. The frame, if we can call it that, is a large retangular can from a surplus store.

Since he and his buddies are running this thing for hours in 100 degree + temperatures, short term solutions won't work. Additionally, everything is encased in that oversized ammo can with two exterior vents. So he doesn't really get an "A" for applications in innovative thermal management.

Anyway, I had considered heat pipe and cold plate for the controller and receiver . . . but being only a ME I can't come up with something that will keep the encased electronics cool when the ambient temperature is over 100 F without using a small generator to provided the needed power. Then suddenly his little automated ammo can becomes a big engineering project.

I am honestly stumped.

[NoodleKnight]

Paint it white, the olive drab ammo canister probably absorbs quite a lot of heat from the sun. Additionally, you can channel the heatpipes to the ammo can so that the heat spreads throughout the metal shell (I'm assuming it's metal, since I've never seen a plastic ammo box). 100*F for electronics isn't really bad for electronics, now if it were 100*C...

[KenWittlief]

why does it need to be enclosed in a can?

Drilling ventilation holes would work wonders.

[Al Skierkiewicz]

I like the drilling holes idea but it takes away from the asthetic value of the the ammo can. You can add fins (painted to match) to the outside of the can so that airflow will cool the exterior, then mount the electronics (the hot bits) on the interior of the can.
Some kind of scoop intake on the bottom would be out of sight and vent holes on the top would allow convection cooling to remove some of the internal heat as well.

[KenWittlief]

Originally Posted by Al Skierkiewicz

I like the drilling holes idea but it takes away from the asthetic value of the the ammo can. ...

OK then, bullet holes would work too :^)

BTW, what is it thats producing the heat? the motors or the electronics?

most small hobbie motors have built in blowers. If they dont get fresh air for cooling it defeats the purpose.

If its the electronics, are you sure you really have a problem? If it runs for 2 hours its pretty much heat-soaked to steady state. If its still running at that temp it might be ok.

Most electronics will operate at 95°C without failing (too hot to touch).

[billbo911]

Originally Posted by Al Skierkiewicz

I like the drilling holes idea but it takes away from the asthetic value of the the ammo can.

Originally Posted by KenWittlief

OK then, bullet holes would work too :^)

Why not combine your ideas? An Ammo can riddled with bullet holes seems to fit the theme. You get "aesthetics" and function.
If you are not the shooting type, but still would like it done, look me up. I'm sure we could arrange something.

All "funnin'" aside, can you post a picture of your son's project, it might help us help you find a solution.

[Gene]

Originally Posted by KenWittlief

OK then, bullet holes would work too :^)

BTW, what is it thats producing the heat? the motors or the electronics?

most small hobbie motors have built in blowers. If they dont get fresh air for cooling it defeats the purpose.

If its the electronics, are you sure you really have a problem? If it runs for 2 hours its pretty much heat-soaked to steady state. If its still running at that temp it might be ok.

Most electronics will operate at 95°C without failing (too hot to touch).

Good question Ken. The motors venting heat into the container; the radiant energy coming off the “desert” floor (which can go up to 120 F.) and the direct sunlight. Remember, this is the place where you can’t go barefooted in the summer because you’ll burn the bottom of your feet (second degree burns!!). Moral of the story - If you live in the southwest – live near the ocean or in the mountains.

Anyway, if he insulates his ammo-bot, he protects it from the direct sunlight. If he draws in outside air, he pulls in the hot air radiating off the ground. If he insulates the entire unit, he protects it from the radiant energy – but bringing in outside air is a no-no because the outside air is merely heats the electronics.

He also asked how they’re keep the electronics cool in Iraq. Needless to say, he didn’t like the answer. But I assured him, I had found a great web-site used by some of the brightest minds in the world and since I was at a loss (short of redesigning the ammo-bot) . . . . the forum is his last and only hope.

You see how much faith I have in you guys!!

[sanddrag]

I don't know what size your motors are but if they are standard hobby RC car size you could try something like this with a small electric pump and tank. Do you have a picture of this robot?

EDIT: Actually, isn't there a way to make a fluid flow through a small cooling system just by using the heat (no pump required)? I think I've heard of that before, but I don't remember the details.

[lukevanoort]

Originally Posted by sanddrag

I don't know what size your motors are but if they are standard hobby RC car size you could try something like this with a small electric pump and tank. Do you have a picture of this robot?

EDIT: Actually, isn't there a way to make a fluid flow through a small cooling system just by using the heat (no pump required)? I think I've heard of that before, but I don't remember the details.

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.

[Al Skierkiewicz]

Originally Posted by Gene

Anyway, if he insulates his ammo-bot, he protects it from the direct sunlight. If he draws in outside air, he pulls in the hot air radiating off the ground. If he insulates the entire unit, he protects it from the radiant energy – but bringing in outside air is a no-no because the outside air is merely heats the electronics.

You see how much faith I have in you guys!!

Remember that no matter how hot the surrounding air is, it is still cooler than the dead air inside the box. If you circulate the air through the box it will take the internal temp down to the ambient. Without a cooling system, that is as good as you can get.

[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.

[Billfred]

IANAE, but what about a cheap cooling arrangement, such as this, on a smaller scale? If the tube and tank sizes could be sorted out, it would seem like you could get things a bit cooler.