# Paper clip heatsinking for LM317?



## ezkcdude

I'm going to build my DAC prototype this weekend, but I don't have any heatsinks. First question: Can I get some heatsinks for LM317's at RadioShack? Second question, has anyone here used the paper clip method for heatsinking? If so, how much current/voltage drop does this work for?


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## psilosome

RadioShack lists this TO-220 heatsink as well as this one. But the stores seem to be cutting down on their stock of these sorts of things so you might be out of luck.

 The regulator won't overheat immediately, giving you time to yoink the power if you think it's getting too hot. It's probably worth checking Tagent's power supply calculator to estimate how much heat the thing will shed.

 Good luck with the DAC. I've been following this project as a possible outboard DAC for my Roku Soundbridge.


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## Xakepa

Do you mind elaborating on the paper clip method 
	

	
	
		
		

		
		
	


	




 Depending on the power consumption and drop-out you can safely get away without. My LM7824 was merely hainging on the wires while dropping 2-3V and delivering about 40mA. Once I upgraded to fully Class A biased Diamond buffers (2 pairs of thansistors each buffer, biased at 20mA), my PIMETA is sqeezing ~120mV/24V and even with a heatsink the chip is pretty hot, 50-60C I guess.


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## ezkcdude

I'll be feeding the DAC +/-15VDC using my DIY LM317/337-based PSU (which also doesn't have heatsinks). The input will be stepped down to 3.3V (for CS8416, AD1896, the XO, and digital side of PCM1794), 5V (for analog side of PCM1794), and +/-12V for the op amps (AD8610, AD8065, or AD8033, most likely). It doesn't seem like that much current would be consumed, but I suppose the relatively large step down in voltage could make a difference here.

 Oh, as for the paper clip, I think you just attach a paper clip directly to the regulator. I'll look for those TO-220 heat sinks first.


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## Garbz

Paperclips aren't very good heatsinks 
	

	
	
		
		

		
		
	


	




 If you have a sheet of aluminium at home grab some tinsnips and cut a strip, fold the strip in half and clip it on the heatsink. It's nasty but it works well while you buy proper heatsinks.


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## Voodoochile

If it's not dissipating much, you could get away with just the reg in free air. I have a little regulator that's been running that way for several years. But if it running very warm at all, almost anything would be better than a paperclip. It's not even making good contact, let alone being a poor conductor.

 Epoxy a penny to the tab if you can't find a clip-on sink... or fold one from some aluminum flashing or a beer can. Extreme ghetto heatsinking, but still an improvement over a paperclip.


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## tangent

Quote:


  Originally Posted by *Voodoochile* 
_Epoxy a penny to the tab if you can't find a clip-on sink..._

 

I was (and am) dubious about this.

 A heat sink only helps to the extent that it improves heat transfer from the heat source to another medium belonging to someone else, thereby making it Not Our Problem. The room's air is a popular choice among engineers, because the engineer doesn't pay the A/C bill.

 For passive heat sinks, the only way to improve heat transfer is to add surface area. So the question is, how much does a penny change the surface area of a TO-220 part? Considering just the metal parts (the plastic doesn't conduct heat well enough to matter), very roughly speaking, it doubles the surface area. Now, you get full benefit of that _only_ if there is no thermal resistance between the penny and the IC. That isn't going to happen, so I suspect most of the benefit is wiped out, especially if you use something with poor thermal conductivity like epoxy.

 You know, if you have a hot enough iron, you could literally solder a penny to a TO-220's tab. That would probably save this idea.

 Needless to say, a penny's worse than useless for any bigger package.


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## nikongod

people used to use window-weld to glue computer chips to their heatsinks. glue is great.

 gluing a peny on would be cool if it was just to prevent the part from burning up from a MOMENTARY short (like unplugging) but i agree a peny would be too small to use as a legetimate solution.

 tehre are also purpose built clip on heatsinks that are much smaller.


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## ezkcdude

Here's another enigma. How does one go about determining if the regs or other components are getting too hot? I certainly don't think the "finger touching" method is a good idea.


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## cerbie

I think the first linked Radio Shack HS is a nice one. Based on the Digikey listeing of the same item, it's 17.4C/W. If Radio Shack doesn't have one on hand, try stocking up on that and other stuff over at Futurlec (limited but useful selection, very good prices, fast and cheap shipping, and decent packing). Once your order hits $5 sans shipping, you'll have beaten Radio Shack pricing.

 Too hot: good question. I've gone with the non-grounded finger method, so far 
	

	
	
		
		

		
		
	


	




. Generally, though, estimate the power needs, and get a HS that can handle that and more. If it doesn't have to be pocketable, a bigger heatsink generally won't hurt. Mainly because you don't want to find out by it shutting off.

 If my math isn't too shabby:
 deltaT/W - ICR - PasteR = Rating in C/W

 Let's call the LM317 (ICR) 5 degC/W and grease 0.5 in degC/W (I think both are actually lower), and deltaT as 50 degC (keep it below boiling). So:

 W = 50/(5.5+Rating)

 Plug in and get a low estimate of max power consumption. Then, some heatsinks may be eliminated, or you may be able to use any one that fits. The first linked RS HS should get you to a max of 2.2W wasted on the regulator.

 With separate ICs doing the job for each section, it likely won't be too bad.


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## Xakepa

-A penny (brass) and TO-220 (tinned copper if I'm not mistaken) have different coef of thermal conductance, deltaT per W. Well might be that tinned copper is a better thermal conductor than (an oxydized) brass, have to look in the book

 -The surface could be twice as big, but also could be much more - all you have to do is to scratch the penny with a Dremel or a rough file. Surface could easily go up tenfold, so the thermal conductance. I love to scrub the paint and scratch the bottoms of the heatsinks in my computer

 -From my expirience, if you don't use smth like Arctic Silver (which I do), the contact b/w the penny/heatsink and the chip will be a major bottleneck, no matter how large of a heatsink you're going to get

 -I'll be curious to see degradation curves for some of those chips, but from my (modest) expiriece electrolytic capacitors are suffering from heat the most, while output transistors can run very hot (above 60C) for many years with no audiable degradation of the sound

 Just my 2c


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## blaken

just go to your local compusa or something similar and buy a north bridge heatsink. One without a fan. Then cut it up with a dremel. Use a little super glue on the edges and your good to go. I would also put a little thermal grease between the heatsink and chip. You could also buy video ram sinks but they would probably be more or even an old socket 5/7 cpu heatsink if you could find one.

 That penny thing is just a bad idea.


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## Garbz

Quote:


  Originally Posted by *ezkcdude* 
_Here's another enigma. How does one go about determining if the regs or other components are getting too hot? I certainly don't think the "finger touching" method is a good idea._

 

Why not, burn your finger, too hot 
	

	
	
		
		

		
		
	


	




 Although yeah it would be a problem if the tab of your regulator or transistor sits high than 50V, if you aren't careful and provide a path to ground that is. If you use silicon or a different isolator between the part and the heatsink like I often do than this isn't a problem.

 I use the KProbe on my multimetre to take a temperature reading.


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## tomb

Quote:


  Originally Posted by *Xakepa* 
_... snip ...
 -The surface could be twice as big, but also could be much more - all you have to do is to scratch the penny with a Dremel or a rough file. Surface could easily go up tenfold, so the thermal conductance. I love to scrub the paint and scratch the bottoms of the heatsinks in my computer. ... snip ..._

 

I doubt this is the case. The Reynolds # confirms that the size of air molecules is fixed. For instance, increasing surface area by thinning fins has no improvement unless you make certain there is also a corresponding space for the air. Your scratches will still be seen as a single surface by the air molecules. In fact, heat transfer may be inhibited, because the optimum surface area _exposed to the air_ is actually a smooth surface.

 This is analogous to the use of thermal grease - the greatest contact is if the mating surfaces are smooth. Any roughenss will inhibit the thermal contact, and thus, the heat transfer. In the case of contact with air, air is simply another contact surface (although a moving one, hence - _convection_). Increasing the area of that contact surface has benefit, but not through simple surface roughness - those are not "fins."


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## ezkcdude

Real-time updates! I just started building. The CS8416 was easy peazy. Just before I started on SRC4192, I accidentally grabbed the tip of soldering iron with two fingers. Whoops! That fricken' hurt. I'll deal it with later. Back to work 
	

	
	
		
		

		
		
	


	




 .

 Screwed up the first SRC4192...But luckily, I pulled it off the board, and was able to get the second one soldered. Now, I just need to get PCM1798 done and the reset chip, and everything else should be cake.


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## ezkcdude

Well, unfortunately, I won't be able to finish today. I'm missing 100R 0805 resistors, which are in series with the XO. And everything was going so well...


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## Garbz

That value is not all that critical. If you have any other resistors <120ohm they could go there.


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## Xakepa

Quote:


  Originally Posted by *tomb* 
_In fact, heat transfer may be inhibited, because the optimum surface area exposed to the air is actually a smooth surface.

 Increasing the area of that contact surface has benefit, but not through simple surface roughness - those are not "fins."_

 

Hold your fire. I was recommending grooves in the millimeter range, which IMO are big enough to be considered a microscopic increase of the surface. We could argue on the airflow, but (being an experimentalist) I'd rather see the temperature reading (with the same ambient) with and w/o groves.

 If I have time, I could try that...


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## tomb

Quote:


  Originally Posted by *Xakepa* 
_Hold your fire. I was recommending grooves in the millimeter range, which IMO are big enough to be considered a microscopic increase of the surface. We could argue on the airflow, but (being an experimentalist) I'd rather see the temperature reading (with the same ambient) with and w/o groves.

 If I have time, I could try that..._

 

With respect, you missed the point. You can't scale the air molecules. They could care less about a millimeter ... and no, I'm not saying that air molecules are bigger than a millimeter. If you look at some surface roughness charts with respect to air movement - it takes bigger "bumps" than that before the air can see them.

 An aluminum _machined_ heat sink already has an optimum fin size, even accounting for manufacturing and structural considerations. The cost of machining already drives them to an optimum dimension on the heat transfer surface. Otherwise, they'd be selling heat sinks with sandpaper finishes.


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## ezkcdude

Quote:


  Originally Posted by *Garbz* 
_That value is not all that critical. If you have any other resistors <120ohm they could go there._

 

I wish I did. I didn't have any 0805 in that range.


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## Xakepa

Quote:


  Originally Posted by *tomb* 
_They could care less about a millimeter ... and no, I'm not saying that air molecules are bigger than a millimeter. If you look at some surface roughness charts with respect to air movement - it takes bigger "bumps" than that before the air can see them._

 

I got it. That seems counter-intuitive at first untill I realised that the flow is so slow it could be insensitive to the surface roughness.


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## tangent

Okay, enough speculation. Time for some actual science.

*Test Setup*
 Six LM317s configured as 0.125 A current sources propped up by silicon diodes. The diodes are there to make the numbers come out nice: with 10 V across the circuit, 1.25 V is dropped across the current-setting resistor, ~0.7 V is dropped across the diode, leaving a nice, round 8 V across the regulator. Since the current through the regulator is nominally 0.125 A, that makes for a very easy to handle 1 W. Ya might think I planned this or something.







 From left to right, front to back, the configurations are:

 1a. Naked regulator; b. paper clip heat sink. (It was easy enough to change from one to the other that I didn't bother making separate board instances for these two.)

 2. 4x penny heat sink.

 3. Aavid-Thermalloy model 577202B00000G heat sink. 

 4. Penny bolted to regulator.

 5. Penny epoxied to regulator.

 6. Penny paper-clipped to regulator.

*Results*

 1a: 0.127 A through regulator, 75.0° C
 1b: 0.127 A, 71.3° C
 2: 0.125 A, 55.5° C
 3: 0.126 A, 54.5° C
 4: 0.126 A, 60.0° C
 5: 0.126 A, 61.0° C
 6: 0.126 A, 58.0° C

*Discussion*

 1: The naked regulator is the baseline, and as you can see, it gets pretty hot. This is about as hot as I'd let a chip get before I'd say a heat sink is no longer optional. Adding a paperclip knocked a few degrees off. I'm surprised it did anything at all, actually. It's not terribly effective, but it's literally better than nothing.

 2: This is four pennies bolted together, with nuts in between each penny to give some room for air to get in there. The penny closest to the heat sink is oriented to give maximum surface contact, and the others are oriented higher to get them more into the open air. You might instead orient the pennies in a rosette sort of pattern, but I didn't have enough room here to get away with that. As-is, it's nearly as good as the purpose-made heat sink. It takes some work to put it together, but if it's late at night, you don't have a heat sink, and you can't get down to your local Radio Shack, dig up some pre-1982 pennies, fire up the drill press and get crafty.

 3: Bog standard heat sink. Available lots of places. Works well. Will probably cost you less than what it's protecting. Standard lore says parts will last twice as long for every 10° C drop, so this gives a nice round 4x lifetime increase. It'll literally pay for itself unless you're using some extremely cheap parts.

 4: #2's little brother, and it works nearly as well. You might be able to equal its effectiveness by lapping the mounting surface flat to maximize the surface contact area.

 5: Again, I'm a bit surprised. I would have expected to give up more than 1 degree by using glue instead of heat sink compound. Now, if you're dealing with more than 1 W of dissipation, the penalty here will get larger.

 6: After seeing #1b, this makes sense. It's just adding the surface area of the paper clip to the penny, so you get a few degrees additional drop. You might get another degree or two of drop if you use some heat sink compound instead of allowing there to be an air gap.

*Test Details*

 The regulators are all Fairchild LM317Ts. They're probably even from the same tube.

 Each heat generator was allowed to cook for at least 15 minutes to get it up to thermal equilibrium.

 Temperatures are approximations. I would often see the regulator swing back and forth over about a 1 degree range. The number I give above is my off-hand estimate of the center of the range.

 Where possible, the temperature was measured in the same location. Regardless of actual location, I spent a few minutes on each part looking for the hot spot. The location I used most is down and to the left of the mounting hole, with the temperature probe jammed in the corner between the IC encapsulation and the tab.

 All of the pennies are 1981 or earlier vintage, that being the last year US pennies were made mostly of copper. After that, they're mostly zinc, with some copper plating. (Source) The pennies in cases 4, 5, and 6 are all 1981 pennies made in the same mint. I didn't feel a great need to find identical pennies for case 2.

 In cases 2, 3, and 4, I used a silver-bearing heat sink compound. Not Arctic Silver ®©℠, but something of that sort. In cases 1 and 6, there's nothing added between the heat sink and the regulator. And in case 5, it's a fast-dryng epoxy.

 In all penny heat sink cases, the surface towards the regulator is the reverse side, as it looks like the obverse has more relief. Also, Miss Manners says it's not nice to apply sticky substances to ex-Presidents' faces. (Miss Manners has nothing to say on the topic of power tools, so I'm also okay in cases 2 and 4.)

 All pennies were cleaned in an acid bath to remove dirt and corrosion. I used CLR initially, but switched to a vinegar and salt solution that was recommended on a coin collector's site. I flushed the acid off thoroughly with tap water.

 Holes drilled through the pennies are the same size as the holes through the Aavid heat sink and the regulators' tabs. I used the thinnest screws I had on hand and clipped their length as well as I could using my wire stripper's bolt cutting holes to minimize their contrubution to the thermal bulk. (#2-56 size.) Normally you'd use something more like #6-40, or maybe even #8-32.


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## tangent

Oops, forgot one of the configurations I wanted to test:






 Using 600 grit wet/dry sandpaper, I lapped the reverse side of the previous #6 configuration's penny flat. Then, with a 400° C iron, plenty of liquid flux and about 10 minutes of futzing, managed to solder the penny to the regulator. (I could do it in just a few minutes now that I've figured out the technique.)

 So, what did that do? It saved another degree relative to using heat sink compound: 59° C. Not as much as I'd guessed. Probably more worthwhile at higher wattages.


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## ezkcdude

Tangent, that was great 
	

	
	
		
		

		
		
	


	




.

 So, can I sum it up by saying, it is best to have a true heatsink, but in a pinch, paperclipping a penny to the regulator will do just fine?


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## Xakepa

Mister Tangent,

 Thank you very much for the time and effort.

 From what I see, it's hard not to note that all penny-based cooling solutions are <10% from one another, and an engineering-oriented mind tends to sum this up as "they produce similar results". I guess Voodoochile was right...


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## tangent

Quote:


  Originally Posted by *ezkcdude* 
_Tangent, that was great 
	

	
	
		
		

		
		
	


	




._

 

Thanks, but I'd be careful about drawing conclusions just yet. After writing that up, I began to be more and more bothered by a few things:

 1. There were several places where I opined that a heavier load would show the differences more clearly. Okay, Mr. Smarty, so why don't you test with a heavier load? 
	

	
	
		
		

		
		
	


	




 So I am. I'm up to 2W now, the highest I can do with my power supply without changing out all those resistors, while staying with integral wattages.

 2. I'm not sure I removed all the environmental and human factors, and test method variability. Is 15 minutes enough warmup time? I'm trying 30. The temp probe never settled on a value, and its swings weren't regular. Can I fix this? I didn't use the same probe point each time. I've decided I can't justify that.

 To try and fix all these sorts of problems, I'm using my helping hands to hold the temp probe against the regulator, always in the same position and always at the same angle. In addition, I'm using my meter's data logging function so I can stay some distance away from the measurement. For all I know, my own breathing was affecting it, because as I move around, that changes how much air is moving over the test area!

 3. I swapped #2 and #4, so I can fan the pennies out in the rosette pattern. We'll see if that makes a difference.

 4. I thought I was being cute by rigging the voltages so the test was right at 1 W even. Except that it isn't. The current setting resistors are well within spec (they're more like 1% apart, not 5% as they're allowed to be), but there is still some difference. So, I'm taking the actual current, calculating the correct voltage drop, and adjusting the test voltage to give the same wattage in all cases.

 EDIT: 5. My excuse of not cutting the mounting bolts flush with the nut was thin. I used a different method to cut the bolts so I could get rid of _all_ the excess.

 So, let me redo these tests, and get back to you. It'll take a day or three.


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## ezkcdude

Of course, you're right to check all these things. But, I doubt we're talking order of magnitude differences here. You never know, though.

 I'm sure by the time you get these tests done, I'll have received my heatsinks, but I'll still interested to see your results.


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## Garbz

Tangent I'm not sure what probe you are using but when I check heatsinked parts with my K-type probe, I find it helps to dunk it into some heatsink paste. Every time I've tried this I found the probe settled faster and in some cases on a slightly higher temperature.

 Noadays I just measure temps where a bit of heatsink paste is spread out from underneat the regulator during clamping. As always milage may vary.


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## tangent

Quote:


  Originally Posted by *ezkcdude* 
_I doubt we're talking order of magnitude differences here._

 

Ah, no, definitely staying within the same order of magnitude. But, I've redone three of them, and relative rankings have definitely changed. In particular, the lone penny isn't coming out so good. I'm not saying more...I need to complete the tests before I'm even sure of what I've got.

  Quote:


  Originally Posted by *Garbz* 
_I find it helps to dunk it into some heatsink paste._

 

An interesting idea. This might be enough to get me to start again. Actually, more of a last straw sort of thing. I've been doing better data analysis this time around, and I'm finding weaknesses in the test method again. Just one example: my gathered data isn't strictly following a Gaussian curve. There's no reason this shouldn't be Gaussian, so the method's got to be flawed. Most likely I either am not taking enough data samples, or I still haven't eliminated all the external variables.


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## ezkcdude

Actually, since your doing these tests, anyway, could you try a setup with a paperclip and a piece of aluminum foil? I would think this would beat the penny.


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## tomb

Very entertaining and useful, Tangent!


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## Voodoochile

Well tangent, I guess you are all caught up on other projects, eh? 
	

	
	
		
		

		
			




 That's pretty nice experimenting.

 I was half joking when I suggested the epoxied penny. I don't think it's a good idea. But I did think it would be better than a paperclip. Although the contact area would be far from optimal, it's a lot better than a paperclip. And then the thought of the paperclip falling off, and landing somewhere around the legs of the reg... 
	

	
	
		
		

		
		
	


	




 Of course it's best to buy a proper heatsink, and for a little device like that, they are cheap. But I guess if I absolutely could not find one locally, and shipping was horrible, I'd make one somehow. Probably not out of clips though.

 I once saw a fairly detailed article about some guy who made a heatsink for a graphics card out of the better part of a roll of pennies. It was just plain scary looking.


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## tomb

Quote:


  Originally Posted by *Voodoochile* 
_... snip ...
 I once saw a fairly detailed article about some guy who made a heatsink for a graphics card out of the better part of a roll of pennies. It was just plain scary looking._

 

Not quite as scary as the thing that guy in your avatar built (Oppie).


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## tangent

Quote:


  Originally Posted by *Voodoochile* 
_Well tangent, I guess you are all caught up on other projects, eh?_

 

Of course not. This is pure, unadulterated procrastination in action.

 Oh, was that my outside voice? Um, I mean, I had constructed a scenario to evaluate the operation of my test equipment. Yes. That's the one.

  Quote:


 I was half joking when I suggested the epoxied penny. I don't think it's a good idea. 
 

It's going to come out better than nothing still, I'm sure of that. Just not quite as high up the rankings as in the original test, I think.

  Quote:


 Although the contact area would be far from optimal, it's a lot better than a paperclip. 
 

I think the reason the paperclip does so well is that it has a lot of surface area away from the regulator, in contact with the air. Most of the surface area of the penny is just mimicking the TO-220's tab, so no advantage.

  Quote:


 And then the thought of the paperclip falling off, and landing somewhere around the legs of the reg... 
	

	
	
		
		

		
		
	


	



 

Okay, so you find a copper paper clip, then you get a really hot iron, and.... 
	

	
	
		
		

		
		
	


	




  Quote:


 Of course it's best to buy a proper heatsink 
 

Yep. Even the little 21 cent Aavid is still beating out all the DIY hack-jobs.


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## Voodoochile

How about this one tangent. Take a penny, and place it on top of the silicon package, against the side of the tab facing the part number labelling. Mark and drill the hole there.

 Then drill a second penny to match, and bolt the two of them so that they are more up in the air, with the gap between them formed by the tab rather than a nut.

 Finally, tighten it to 65 foot-pounds. 
	

	
	
		
		

		
		
	


	




 I've got to admit that while the clip did not perform that well, I am surprised that it dropped the temp that much.

 Have you considered some 16g solid wire to make your own copper clip? I suppose that would defeat the idea of using what you have on hand (eg, clip or penny).

  Quote:


  Originally Posted by *tomb* 
_Not quite as scary as the thing that guy in your avatar built_

 

No kidding. I'd not want to have that on my resume, brilliant as it was. Very interesting fellow, though.


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## tomb

Quote:


  Originally Posted by *Tangent* 
_I think the reason the paperclip does so well is that it has a lot of surface area away from the regulator, in contact with the air. Most of the surface area of the penny is just mimicking the TO-220's tab, so no advantage._

 

That is absolutely the key. I'm with Voodoochile on raising the pennies, though. Just rotating one up to the tab part of the regulator would get some interesting results, I think.


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## ilikepie

Ive used staples as a heatsink and it helps a little. If your gonna use pennies you can stack them zig zagish to increase surface area. Glueing them on is a pain though. I use these heatsinks for my computer because im too lazy to glue staples on all day, they come with some tape, and its cheap.

http://www.svc.com/crc-u01.html


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## luvdunhill

I'm looking to step up from the 24.4 C/W heatsink recommended on the TREAD by Tangent, and was thinking about using this one but mounted "the wrong way" (i.e. the fins sticking out away from the board).. this gets my thermal resistance down to 9.6, but I was wondering a couple things:

 1.) Does this really matter since I will not be using a fan, so I will not have any air velocity (see the graphs for the part above)

 2.) Is there another heat sink that would "fit" on the TREAD? The larger style used on the STEP doesn't look like it will even come close to fitting!!

 Thanks!


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## Nordic

I was testing my valve pre one night when my wife asked me why the tube was glowing so brightly, which surprised me as it was an ecc88 and they don't realy glow like that... or none that I have seen next moment I got the hot electronics smell from the regulator board supplying the 6V heater.... I forgot to attach the heatsink... and it swung to full voltage output... luckily it didn't do any permanent damage to the valve or the regulator.


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## tomb

Quote:


  Originally Posted by *luvdunhill* 
_I'm looking to step up from the 24.4 C/W heatsink recommended on the TREAD by Tangent, and was thinking about using this one but mounted "the wrong way" (i.e. the fins sticking out away from the board).. this gets my thermal resistance down to 9.6, but I was wondering a couple things:

 1.) Does this really matter since I will not be using a fan, so I will not have any air velocity (see the graphs for the part above)

 2.) Is there another heat sink that would "fit" on the TREAD? The larger style used on the STEP doesn't look like it will even come close to fitting!!

 Thanks!_

 

Luvdunhill,

 The TREAD and the TO-220 LM317 are more flexible than you think. The heat sink you reference will work fine - assuming, as you say, it will fit. Even so, that's not really an issue unless you're trying to pack all this into a mint tin.

 You can bend the leads on the LM317 so that it lays flat, away from the board, or even mount it in reverse on the bottom of the TREAD board (make sure the polarity is correct). Almost any heat sink will fit in those scenarios. If not, there's nothing that stops you from drilling another hole in the heat sink so that you can bolt it where it does fit. If your case is metal, you can delete the heat sink altogether and bolt the LM317 directly to the case. The mass of the metal will cool it better than most heat sinks.

 If anything, this thread highlights the almost limitless flexibility of applying a heat sink design.


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## Garbz

Quote:


  Originally Posted by *Nordic* 
_I was testing my valve pre one night when my wife asked me why the tube was glowing so brightly, which surprised me as it was an ecc88 and they don't realy glow like that... or none that I have seen next moment I got the hot electronics smell from the regulator board supplying the 6V heater.... I forgot to attach the heatsink... and it swung to full voltage output... luckily it didn't do any permanent damage to the valve or the regulator._

 

Your wife knows how bright a tube should glow? My girlfriends mostly have no idea what a tube is! 
	

	
	
		
		

		
		
	


	




 Btw Tangent as a matter of interest what is your background in statistics? It seems you know quite a bit about data samples and expectation.


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## tangent

Quote:


  Originally Posted by *Garbz* 
_as a matter of interest what is your background in statistics? It seems you know quite a bit about data samples and expectation._

 

Most of my technical training came from this book.

 I don't actually remember where I learned what I based my expectation on. It just seems to me that since it's a natural, linear system, it's most likely to be Gaussian. I'm not ruling out the possibility that it inherently has another distribution, perhaps because of some quirk of the way the regulator works. Let's just say that if I improve my techniques and start getting proper Gaussian distributions, I'm not going to be surprised at all.


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## Nordic

Well i was assembling the thing on the floor.. she did see me testing subsections of it earlier... but man those heaters wire bright. Gave me alot of respect for how tuff the tubes are.


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## Tomo

Hey,

 Just for a record LM317 should work fine well beyond 100C (temperature compensated). ... In essence, keeping it free in air is fine according to Tangent's results. (Will you right a short paper for me? So I can refer to it.) 

 Nordic, you said your ECC88 glow hot. How are you powering the heaters? If you are using the LM317 current source like in the original YAHA amp, you may have wired it upside down. Check the wiring anyway. The glow like that comes from the tube heater getting massive current. This will fuse your heater coils. 

 I had a similar problem and I had it running for a week. Now I have Ei ECC88 with heater voltage of 1.8v(!!). This put approximately 12V across my LM317. This is no-no because voltage across the regulator is directly related to dissipated heat. I had my LM317 bolted to the aluminum chasis so the entire amp was hot to touch. I had to chuck the Ei tube out.

 T


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## Nordic

No, the circuit was running fine, I think it was some form of thermal shutdown in the regulator that kicked in...when I let it cool down and put the sink back on it worked just fine...the heaters are just glowing faintly orange, I think it is about 365mA, but its been a while since I build it, so I'm not 100% sure. Works beautifully and is in daily use from about 8in the morning till 1 at night. I think I had a current limiting resistor in parallel just before the tube and I basicaly adjusted the regulator with the tube pluged in and dailed it to 6V.


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## cetoole

Quote:


  Originally Posted by *Voodoochile* 
_Have you considered some 16g solid wire to make your own copper clip? I suppose that would defeat the idea of using what you have on hand (eg, clip or penny)._

 

That could be interesting to see. I have some 14awg solid copper, uninsulated and unenamled, so it would be pretty easy to use for heatsinking. I forget where or why I got it though. I would guess that it would do better than a penny sink, if done right, but I have no way to test it though. Some of those cheaper DMMs I have looked at while searching for a cheap hFE meter have temp probes, but I have no idea how accurate they are.

 Tangent: What kind of temp. probes are those? Also, I cant tell from you writeup where you measured the temperature from. I wonder how much additional heatsinking effect you get from the contact with the probes. Very interesting results so far though.


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## tangent

Quote:


  Originally Posted by *cetoole* 
_What kind of temp. probes are those?_

 

It's a 5W thermistor. This type is made more for measuring the temperature of liquids, but I like its ergonomics better than the bead type ones that are standard for this meter.

  Quote:


 I cant tell from you writeup where you measured the temperature from. 
 

I said above that one of the flaws in the original test is that I measured in several places, for a reason that seemed good at the time, but which I've rejected. My new test will measure from a single place.

  Quote:


 I wonder how much additional heatsinking effect you get from the contact with the probes. 
 

A significant amount, no question, but it's the same for every test, so it nulls out.

 The only practical problem here is that the numbers I'm measuring aren't the actual values, but reduced somewhat. Between that and the fact that I'm not actually measuring junction temperature, you shouldn't use that to determine how close the regulator is to overheating. The junction temperature will certainly be higher.


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## tangent

I redid the measurements over a week ago, but just now got around to rewriting the results. I decided to make it an article on my site, if only because of the amount of work that went into it. There's more detail in the new article than my posts above, and I've also published the raw data and a partially-distilled version of same, so you can get a more nuanced picture than I gave earlier.


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## Voodoochile

That's great, Tangent! It was informative, if not practical. It does offer a very nice illustration of how different (albeit unorthodox) sinking methods can vary.

 It would be interesting to see a similar test conducted with one heatsink: without any paste, with past, with epoxy, with superglue, with thermal epoxy, etc. Just to show that even having a proper heatsink does not guarantee a given level or performance, depending on how well you affix it.

 That was not a suggestion, really, it was more a case of thinking out loud.

 Nice job.


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## ezkcdude

Quote:


  Originally Posted by *tangent* 
_I redid the measurements over a week ago, but just now got around to rewriting the results. I decided to make it an article on my site, if only because of the amount of work that went into it. There's more detail in the new article than my posts above, and I've also published the raw data and a partially-distilled version of same, so you can get a more nuanced picture than I gave earlier._

 

Great work! Glad to be the "someone at head-fi" who instigated this thought-provoking, if esoteric, article. Tangent, I do have a question. I ended up putting heat sinks on the regulators that were getting hot on my DAC. Maybe I'm paranoid, but at a certain temperature, do those LM317's burst into flames or something? What happens when they get "too hot", and do you know what temperature that might be? My question is really about safety. I am just wondering how safe it is to leave my apartment with DIY stuff turned on (not playing music, though). So far, I've been turning the power (on the surge protector) to my DAC completely off when I leave it unattended.


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## tangent

Quote:


  Originally Posted by *ezkcdude* 
_What happens when they get "too hot"_

 

Read the datasheet: they shut down.

 If you're asking what happens when they shut down, it means the output voltage starts dropping rapidly. If you're riding right on the edge of the thermal limit, you can get a really ugly output as the thing turns rapidly on and off.

 Don't do that. 
	

	
	
		
		

		
		
	


	




  Quote:


 I am just wondering how safe it is to leave my apartment with DIY stuff turned on (not playing music, though). 
 

I wouldn't worry about any commercial IC catching fire. But, if you have things like discrete buffer stages, that probably doesn't have current or thermal limiting built in.


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## ezkcdude

Quote:


  Originally Posted by *tangent* 
_Read the datasheet: they shut down._

 

Yep. "Thermal overload protection" should have given me a clue 
	

	
	
		
		

		
		
	


	




 .


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## cobaltmute

This thread was just indirectly quoted in Gizmodo:

DIY: The Penny as Heat Sink


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