Question on heatsinking - diyAudio
 Question on heatsinking
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 31st January 2007, 12:58 AM #1 diyAudio Member   Join Date: Sep 2004 Location: Savage, MN Question on heatsinking Do you think that a 8" section of the extrution from the r-theta group order a while ago would be sufficent for a single channel A30?
 31st January 2007, 02:22 AM #2 diyAudio Member   Join Date: Jul 2004 Location: Planet Earth I've been asking myself that same question, and I think the R-Theta group buy profile is 9012, so C/W/3" section is listed as 0.6: http://www.r-theta.com/products_stan...m_profiles.asp I'm not sure about the math, but I think this means a 6" section will give you a (ideal conditions) C/W of 0.3 - 100W idle load will raise the heatsink temp to 30C over room temp. Double again to 12" and you should get 0.15 and 15C for a 100W load, so figure between 15 and 30C - closer to 30 under average heat transfer (that's 30C over room temperature) for an 8" section. Some will chime in with a link to the heatsink calculator/simulator and you can plot your heat points etc for a real simulation.
 31st January 2007, 02:36 AM #3 diyAudio Member   Join Date: Apr 2006 Location: Minnesota twitchie, Your assumption is incorrect. The thermal resistance is not inveresly related to length. The thermal resistance of a 6 inch section will be greater than 1/2 the resistance of a 3 inch section. My guess is it will be around .4. There is a link to the R-Theta calculator on the page you mentioned.
 1st February 2007, 05:31 PM #4 diyAudio Member   Join Date: Sep 2004 Location: Savage, MN So I can assume 8" section would be ~.3 C/W and since a lot of people have had success with the big conrad heatsinks listed at .21, but taking into account the 1.4 multiplier since they rate temp different, that makes it effectively .3 I should be fine. Cool, well not cool, but not boiling either.
 1st February 2007, 05:48 PM #5 diyAudio Member     Join Date: Dec 2005 Location: the north hello heatsinkers let's sink the temp Question 1: --------------------------------------- Anybody know of a temperature monitor project? Good if it is a project for monitor power amp heatsinks. - 1 sensor at heatsink, close to Transistors - some indicators: LEDs or maybe - measure millivolt per degree with multimeter at testpoints - digital display (advanced monitor) Question 2: ---------------------------------------- What would be a suitable sensor? - LM35 is a dedicated IC, gives 1mV raise / each degree C but I have been told it is very slow .. like 5 minutes to reach value - BD139, TO-126 transistor could be used, ~2.2 mV / each degree in change of VBE, volt base emitter .. but would need some Op-Amp and some calibration to get a nice scale Regards lineup __________________ lineup
diyAudio Member

Join Date: Dec 2005
Location: the north

I asked a similar question 1 year ago.
Quote:
 Originally posted by Arius Lineup, I'd treat the BD139 as a silicon PN junction diode. In that case, excite it with 10uA. You should get about 2.3mV/degC sensivity with that. --------------------------- The ThermalTraks are supposed to replace this temp dependent bias generator circuit (their internal diodes, that is). .

What Aruis tells me is:
1. I should use only like 10uA current flow in the BD139
if using it as temperature sensor
2. I will get ~ -2.3 mV / degree C in temp raise

----------------------------------------
Original Topic:
On Semi ThermalTrak - Power Transistors

Regards
Temperature Control Department
of
Lineup Audio Lab

-----------------------------------------
Another good topic on heatsink and temp control, temp tracking
where also Nelson Pass contributed some good advice:
MOSFET amp problem - Heatsink and Temp tracking

.

 2nd February 2007, 05:21 AM #7 diyAudio Member   Join Date: Aug 2003 Location: Santa Cruz, California Would that group buy still be open, by any chance?
 2nd February 2007, 11:02 AM #8 diyAudio Member   Join Date: Feb 2006 Location: peak district, england I use a water cooling system with a flow controller to monitor the coolant flow and temperature. This shuts the amp down if things get too hot, or if the flow fails for any reason. I made use of a temperature sensor sold in the UK by Maplin. This may be OK for monitoring a conventional system providing it doesn't get too hot. It is certainly easier than messing about with Vbes, bandgap references, instrumentation grade opamps: Temperature Module This module will display up to 69.8 Celcius and can be rigged to alarm. You can connect an external temperature probe, and there is a display bezel for it too:.
diyAudio Member

Join Date: Nov 2006
Re: Question on heatsinking

Quote:
 Originally posted by Hastur Do you think that a 8" section of the extrution from the r-theta group order a while ago would be sufficent for a single channel A30?
dissipation ability is related to:

1) heathsink surface

2) Air speed flowing on this surface (and hence is dependent on mounting: vertical mounting allow more air flow to run on heathsink surface than horizontal).

Hi
Piercarlo

PS - "Bulkity" of heathsink is more related to its thermal capacitance rather than its surface. More fins act more efficiently of more weight.

diyAudio Member

Join Date: May 2001
Location: Norway, -north of the moral circle..
Quote:
 Originally posted by lineup - LM35 is a dedicated IC, gives 1mV raise / each degree C but I have been told it is very slow .. like 5 minutes to reach value [/B]

Not so.. the chip reacts in seconds- it's the heated mass and your thermal coupling that sets the response.
I use it with good results for measuring internal temp's in sounding rockets!
Any DPM set to 0-1V gives you direct readout of temp. If you want alarms or switch off, use a comparator or a small dedicated DPM.

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