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Hi,
I hooked up only B3 to the HD. One thing I noticed that after a minute or so, QN1 get quite hot while QN2 does barely get warm at all. I have no equipment to measure the exact temerature but I can keep my finger on it for a few seconds (5 or 6) before it begins to feel quite unpleasant.
When I compare this to the HDBP, both heatsinks (QN1 and QN2) dissipate more or less the same heat. For as far as I can see the B3 seems to run just fine. I have not connected any other modules to it yet so I can not be entirely sure about this.
I'm a bit puzzled by this. Is this normal behaviour or could it be that QN2 is broken? Would it even work with just QN1?
These are my measurements:
TP_out --> TP_shunt: 45.3 mA (mV)
TP_Vin --> TP_ccs: 510 mA (mV)
TP_vref --> GND: 3.79 V
V_out --> GND: 5.20 V
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I had asked this same question (but can't find the post) and was told it was normal for QN1 to get hotter than QN2 on the HD. I don't know the reason why, but mine does the same thing and works great. EDIT: I used larger sinks on mine (2.5" tall) and get ~ 55C on QN1 in an open chassis. I am shunting about the same mA as you are. Temp measurements made with a Fluke 52 II meter. IIRC 80C is a max temp. Here you go, post 5. http://www.twistedpearau...0-Mod---In-Progress.aspxEdited by user Sunday, May 27, 2012 4:36:12 PM(UTC)
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Thanks. That is what I needed to hear. Or read. I`m thinking about using a bigger heatsink as well.. or perhaps add a second one to it. Perhaps it is not needed but I don`t like it running this hot. |
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Hi Corprius, Mine gets hotter as well. So much that I coupled an extra heatsink to the already enlarged ones. This is normal behaviour. I was told that 75 deg celcius is about the max it might become. I meassured between the two heat sinks that I coupled and meassured around 60 deg. (I meassured with a core thermometer, same one as you use for the chicken in the oven  ) In the casing the temperature rises to 40 degrees with an OAT of 27 degrees this day's in Holland ;)
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If you have soldered QN1 and QN2 close to the pcb you may have to turn the heatsink up-side down to get complete contact between QN1 and QN2 and its heatsinks. The entire surface area should be in contact with the HS for proper thermal transfer. The added cooling from soldering the heatsinks to the pcb is wasted on the fact that the heatsink does not have proper contact with the surface it is supposed to cool down. As long as the contact is not complete, the heatsink can be the size of a building and still not provide efficient cooling of QN1 and QN2. Edit: Some components run hotter than others. I am not sure what temperature QN1 and QN2 can be stable at but it can be run at lower temperatures by providing complete contact between the surfaces. Edited by user Sunday, May 27, 2012 7:39:20 PM(UTC)
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Well it can radiate it's heat and pass it trough. I file the contact surfaces of both coolers to mate and applied some heat conductive grease. If it don't helps it does'nt bother ;) Jordo attached the following image(s):  double cooler.jpg (146kb) downloaded 32 time(s).You cannot view/download attachments. Try to login or register.
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Hi Jordo and Gwikse,
Now you (Jordo) mention it I remember looking at your double heatsink construction.
I think that I try desoldering the heatsink and buy another larger one instead and make sure that the entire surface of QN1 makes contact with it. I need to get myself one of those infrared thermometers.... |
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Gwikse has a point.
I do'nt remember actually that I confirmed the transistor made full contact. I do thing I fully covered the metal part of the transistor to the heatsink... But it might even be better to cover it completely inclusing the plastic bottom part...
What do you think will happen if it gets too hot?....
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