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Active cooling for DIY boards / boxes


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I know you dont really need it (especially if you have the "full power" heatsink) but im a cheap bastard, and could not convince myslef to spend 20.00 on a chunk of metal. I also know most like to set controllers out in the elemnts, and a fan with air vents would not be desirable - but mine are safe from water, so its not really an issue for me.

So instead of spending another 80.00 to outfit all my controllers with large heat sinks, I have tons of CPU heat sinks and fans lying around that would be easy to attach to my exsisting "low power" stip of metal.

I dont have a degree in thermo dynamics - but I'm willing to bet a CPU fan and cooling block can dissapate as much if not more heat than the "high power" heat sink alone.

I plan to mount 1 block and fan with some thermal paste for each group of 8 channels. I'll probably incase the whole thing in Plexi or Lexan with holes at each end when done.

Just wondering if anyone else has done similar or had issues with cooling.

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Well, I'm not a betting man, so I won't bet against you, but there are more factors than just moving air around inside your controller case.

The reason those CPU fans work inside your PC is that there is air getting moved in and out of the PC case as well. If you didn't have other fans pulling/pushing air in/out, the box would just get hot inside - which is what will happen if you just put CPU fans inside a sealed case with your controller.

The heat still has to get out of the case, and while the CPU fan/heatsink might pull the heat away from the triacs better, it still doesn't help unless you put the heat somewhere. Eventually teh temp will rise inside the case, and correspondingly, the junction temp of the triac will rise too.

So, I'm not sure if it will work or not - depends on the outside temp as well.

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This has a lot more to do with just moving the air. The problem is the triacs create a sort of radiant heat. The reason a heatsink is used, in conjunction with the heatsink compound, is to take the radiant heat and distribute it over a much larger area. The traics, along with the 5 and 10 volt regulators have metal backs. They are designed to move that heat up to a certain amperage. The heatsinks allow you to increase that amperage because the heat is distributed over a much larger area.

Will certainly will be fine with low amperages per channel (around 1 amp) but as you start to increase the amps you will create more heat, which needs some place to go.

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I understand the idea behind moving the air - I know case fans push or pull air in / out of the PC case.

The fan is merely a substitute for the larger "sink" of metal - beyond that both concepts radiate heat into the surrounding area. Even the big heatsink is just a larger piece of metal to dissapate the heat. The basic PC series LOR unit is a closed box. The larger heatsink just heats up the air inside the box - It just happens to be large enough surface are to move enough heat to keep the triac happy.

I'm just betting a fan does it better.

Even in a big plexi box, I would still have an intake and an exhaust fan

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I good example to think of to support what Greg said, think of car radiator or even if you have base board heating. What works better, pipes with fins, or pipes with out fins for dissipating heat. As a hobbiest, and not an expert, I would not push the triacs over an amp with out attaching some sort of medal conductor to it first. I speak from experience, I have melted a lot of IC's messing around!

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I know how a heat sink works, and I know what the "fins" are for.

Let me try to spell this out a bit more clearly.

I am going to take a FAN AND HEATSINK (with little fins) and secure it to the "low power" sinks that came with my ctb16pc, then take that and place it in a box with another set of fans to move hot air out and cool air in.

Im not screwing a fan to the back of a triac.

im not going to stick a box in a hole in the ground and cover it with dirt.

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And just in the spirit of discussion. The reason a fan is used with a heat sink is this. If you have enough wattage of heat being sunk into the heat sink. The efficiency of the heat sink decreases over a certain size. Meaning to get one more watt of heat dissipated you have to almost double the size of the sink. So this is the reason for the fan. It is not an even trade off between fan and no fan on the heat sink.

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IMO - go ahead a try it. You can tell us if it works.

However, if it fails during you holiday season and you lose 1, 2 or more controllers . . . I bet you'll be sorry you took that $80 gamble.
Risk Management - if you can afford the time, then try it.

I personally have used my own heat sinks, but they are very similar to LOR's. My brother had some scrap aluminum that was the same thickness, so he put a 90 bend and I used it without any problems.
Risk Management - I keep an extra controller on hand just in case something happens during the season.

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I am currently using CPU heat sinks on my diy kits. I cut about .5 inch wide strips for 4 triacs a piece and use the old heat sink as a guide to drill holes. They have nice heat dissipation much better than the high power heat sinks, but they do take more room.
In my opinion a fan is overkill as they already have better cooling.
Neil

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Logic tells me that the factory hs (low power) with a CPU sink bolted on + a fan is going to dissapate way more heat than the stock high power HS.

But lets put some science behind it. I can run a 500 Watt load at 90% on chanel 4 for 10 minutes, and then hit the bolt head on the triac with a temp gun.

Is anyone with a "high power heat sink" willing to do the same ?

I dont know how much heat the typical board puts off - (and I know I has much to do with loads and on / off cycles) The only testing I have done with my boards is placing about 1 amp max load for a short time, and I cant even feel the triac get warm.




Attached files 211368=11783-lorsink.jpg

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gizmomkr wrote:

Logic tells me that the factory hs (low power) with a CPU sink bolted on + a fan is going to dissapate way more heat than the stock high power HS.

But lets put some science behind it. I can run a 500 Watt load at 90% on chanel 4 for 10 minutes, and then hit the bolt head on the triac with a temp gun.

Is anyone with a "high power heat sink" willing to do the same ?

I dont know how much heat the typical board puts off - (and I know I has much to do with loads and on / off cycles) The only testing I have done with my boards is placing about 1 amp max load for a short time, and I cant even feel the triac get warm.


I would tell you to place the heatsink directly on the triacs as heat transfer would be much better, but i guess it seems to be doing the trick without placing t directly on.
Neil
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I guess you could also put a 457 on your child's go cart and it would preform better. I'm sure the LOR guys have done all types of heat test that shows what is needed to dissipate the heat at different levels.

Stop trying to reinvent the wheel and work on something that has not been perfected.

Build a new effect, give us another Weber tree design; something that we can benefit from.

The hardware is done! Give me something that can really effect my show, not something that can save me $20 a board. I have thousands of dollars in this investment. I want to WOW people, not cut corners or over engineer a piece of hardware. Our guess can't see any of that!

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Scott T wrote:

I guess you could also put a 457 on your child's go cart and it would preform better. I'm sure the LOR guys have done all types of heat test that shows what is needed to dissipate the heat at different levels.

Stop trying to reinvent the wheel and work on something that has not been perfected.

Build a new effect, give us another Weber tree design; something that we can benefit from.

The hardware is done! Give me something that can really effect my show, not something that can save me $20 a board. I have thousands of dollars in this investment. I want to WOW people, not cut corners or over engineer a piece of hardware. Our guess can't see any of that!


gizmomkr,

do as you wish needless to say. But if you really want to make a difference, then read and heed what Scott T said above. This gent has given you the best advice that anyone can in this hobby.
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Neil Amin wrote:

I am currently using CPU heat sinks on my diy kits. I cut about .5 inch wide strips for 4 triacs a piece and use the old heat sink as a guide to drill holes. They have nice heat dissipation much better than the high power heat sinks, but they do take more room.
In my opinion a fan is overkill as they already have better cooling.
Neil


Neil,

Also in the spirit of discussion. What if the orintation of the heat sink does not promote convection cooling (does not promote the flow of air over the fins). Example a vertical hear source but the heat sinks fins are horiz. The air can not rise easily. But if the fins are vertical then the air rises up along the fins and exits the top of the heat sink. A fan will be needed to move the air over the fins if the fins are not in a vertical orintation. And yes forced air flow is still going to win hands down over rising hot air that is replaced with cooler air (aka natural air movement).
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I only skimmed the replys in this thread so this may be redundant.

The cpu heatsink with fan running will get rid of more heat than the High Power heat sink and most likely will work well.

I think this will work well and only have two concerns.

1. The triacs on the ends will run hotter than the rest of the triacs. Without testing or a sophisticated modeling software it is not possible to tell if this will be a real issue.

2. Most of the fans of that type are designed for indoor use. So it is difficult to say if they will start running when exposed to cold weather.

Dan

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Scott T wrote:

I guess you could also put a 457 on your child's go cart and it would preform better. I'm sure the LOR guys have done all types of heat test that shows what is needed to dissipate the heat at different levels.

Stop trying to reinvent the wheel and work on something that has not been perfected.

Build a new effect, give us another Weber tree design; something that we can benefit from.

The hardware is done! Give me something that can really effect my show, not something that can save me $20 a board. I have thousands of dollars in this investment. I want to WOW people, not cut corners or over engineer a piece of hardware. Our guess can't see any of that!


I dont quite follow Scott - your first post tells me "I made my own ... out of scapp aluminum" (saving you 20.00) Your next post is telling me not to re invent the wheel and you have thousands invested, and that saving you 20.00 is a waste of time, and I should spend my time working on a neat looking effect. Sounds somewhat hypocrytical to me... but thats really besides the point.

I dont have thousands of dollars to invest - I'm happy I could find room in my budget for what little hardware I have. I never said "LOR makes a lousy heat sink, Im going to make one better" I just want to recycle some of my "junk" into something I can use, and maybe save enough cash doing that to buy anotherr controller.

I DO want to cut corners - everywhere I CAN. My first year dooing this, I couldnt afford to waste money buying female edison connectors at the last minute from homedepot, I would have spent a couple hundred bucks. Instead I cut the ends off all the extension cords, and the light strings, and bought a big box of wire nuts. everything was wrapped in E-tape, and it worked fine. It was a pain, but it let me save that money for something else.

Anyway back to the point of this thread - I will be attaching 1 or 2 old CPU sinks like in the picture, and some fans. i'll post the results with some temapture readings when i get it all done for anyone thats interested.

Thank You to the others for your helpfull and technical advice.
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gizmomkr wrote:

I dont quite follow Scott - your first post tells me "I made my own ...  out of scapp aluminum" (saving you 20.00) Your next post is telling me not to re invent the wheel and you have thousands invested, and that saving you 20.00 is a waste of time, and I should spend my time working on a neat looking effect. Sounds somewhat hypocrytical to me... but thats really besides the point.


I did not change the design!
I duplicated and offset my risk with a back up controller. Risk management!
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Wow, you guys aren't very supportive. It might very well work just fine.

The concerns that I would have though, CPU heatsink/fans are meant to cool mostly the center and less on the ends. The heatsink is too short so the outer TRIAC's aren't going to see the same cooling capacity. You need at least a couple inches of clearance for the fan or you won't get the full air flow.

I would run the outside 4 channels at 6 amps each and check that the outside TRIAC tabs never go over 120 degrees while inside your case. 12 amps would be 80% of a banks full load. If all for TRIAC's stay below 120, I would feel reasonably confident that a normal sequence would never cause excessive heat. I would feel more confident if you could look at it with a thermal camera though.

Of course there's still no guarantee but TRIAC's aren't that hard to replace.:?

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  • 4 weeks later...

Being in Atlanta it probably won't get too cold for the cpu fans to start up but that would be little bit of a concern as LOR Dan said. I think it is a great idea. Up here in Missouri last Christmas saw temps close to zero and my animated wire frame and a couple of inflatables had trouble running.

Everyone has different priorities, skills, and resources. Many years ago I had saved a bunch of water cooled mainframe "cold plates" that used chilled water to cool power supplies. I figured I could use them down the road and recently thought controlling Christmas lights might be the perfect use. In the end though, they would be way overkill, but still fun to think about and a great way to impress people :P.

In the end I chose to use DIY kits without enclosures because I wanted to keep the controllers safe and sound inside the garage. I spent the money I saved on enclosures on the cable to get the power where I need it using bulk 16awg zip cord (longest run of 150ft). I cut a cheap extension cord in half to get the power plugs on both end of the zip cord by soldering and using heat shrink tubing to seal the connections.

I seem to be in the minority putting my controllers inside but this works well for me. I don't have to worry about water, heat dissipation, or someone walking off with my controllers.

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Steve Gardner wrote:


I seem to be in the minority putting my controllers inside but this works well for me. I don't have to worry about water, heat dissipation, or someone walking off with my controllers.


Funny you mention that Steve, had a neighbor ask me if someone stole my controllers what could they get for them? I told them, they probably wouldn't get a thing out of them as they require a computer and specialized software to make them work. They'd only be valuable to someone like me that knows what they are and how to program them.

So yes, my controllers are outside, but they are also LOCKED with a lock and also secured by bolts to a wall, except for two which are secured to the back of two old converted wooden ammo boxes, but then, they are all tied together with cat5, cable ties and cords cable tied, so if someone were to want to try and steal them, it's going to take them a lot of work to get them or anything else in my display. They could do damage, but they couldn't get off witrh anything without a whole lot of trouble and problems getting it loose!



As for the persons fan idea, if it were me I'd be installing no less than three fans near the triacs, one centered and one each end, this would keep the entire set cool. Especially if he has a lot of them lying around around. Then of course there is the fourth fan for the ventilation (blow the hot air out) and then a fifth for blowing cool air in. Personally, waste of time, it just would have been smarter to spend the $20 for the HD heatsinks that LOR installs. And that's what I did, bought all my CTB16PC's assembled and with the heavy duty triacs installed. And I have tons of those fans around too and had thought about it, but having been in electronics for over 35+ years, I knew the BEST way to go was with the way LOR has it! There are times when saving a buck IS NOT the way to go, and for me, this was definitely one of those times NOT to save a buck!

The time and effort to place fans and smaller heatsinks just wasn't worth the risk of frying triacs and murdering my shows!
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gizmomkr wrote:

I know you dont really need it (especially if you have the "full power" heatsink) but im a cheap bastard, and could not convince myslef to spend 20.00 on a chunk of metal. I also know most like to set controllers out in the elemnts, and a fan with air vents would not be desirable - but mine are safe from water, so its not really an issue for me.

So instead of spending another 80.00 to outfit all my controllers with large heat sinks, I have tons of CPU heat sinks and fans lying around that would be easy to attach to my exsisting "low power" stip of metal.

I dont have a degree in thermo dynamics - but I'm willing to bet a CPU fan and cooling block can dissapate as much if not more heat than the "high power" heat sink alone.

I plan to mount 1 block and fan with some thermal paste for each group of 8 channels. I'll probably incase the whole thing in Plexi or Lexan with holes at each end when done.

Just wondering if anyone else has done similar or had issues with cooling.

I have built heat sinks for LOR controllers before... BUT I did take some things into consideration when I did so. I used the chunk of metal approach with a high dollar finned heat sink extrusion material (but I had it on hand).
After seeing the time I spent doing the machining... I just save up and just buy the punch press and metal break version LOR sells. :D

Your method may work fine... I am not going to say it won't since I have no idea what your loads are, or what your sequences look like.
Ernie kind of touched on this with his reply, in that my concern would be that the end channels may not really see much effect from your add on heat sink.

The issue is that the low power heat sinks are thinner aluminum then the high power heat sink, and as such will not be able to "transfer" or conduct as much heat from the triac junctions (the real purpose) to your add on heat sink. Add the thermal resistance increase caused by the fact that you are bolting 2 separate pieces together (even with grease) and the overall application is not as nearly as efficient as the "chunk of metal" approach is. (even with airflow)

Again this all goes back to your load... if it is low enough that you don't "saturate" or swamp your heat sink set up with more heat then it can transfer then you are fine.

Is the add on going to allow you to cool better than the low power heat sinks alone?
To some extent... yes.

Is it as good as the high power heat sinks? I doubt it very much...
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gizmomkr wrote:

Scott T wrote:
... I will be attaching 1 or 2 old CPU sinks like in the picture, and some fans. i'll post the results with some temapture readings when i get it all done for anyone thats interested.

I think we would all be interested in the results. It's one thing to speculate and another to see the proof.

One other thing you might think about is that by itself the heatsink is too small, do you have something to tell you if the fan fails? They do fail and with a PC, you can have software shut it down if the fan does fail for any reason. You'll need something in place to deal with this.
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  • 4 weeks later...

Just food for thought. If the high powered heat sinks are mounted directly to the side/back of a good “metal” box, then you would be far better off???



Yes / No??



Have a good one..



Mikey

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  • 3 weeks later...

If I were you I would try to figure a way to transfer the hest from the heat sinks in the housing to a heat sink on the outside without compromising the weather tight housing thus creating a natural cooling cycle.

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