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FrozenGate by Avery

For those having trouble with Overheating Dummy/Test Loads try this Mod.!!!

Joined
May 25, 2010
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Hi All,

Well about a week ago i realized when trying to set a driver to a higher amperage the dummy / test load Keeped on getting super hot really quickly. The test load got so hot After about 5 second that i had to take breaks after that 5 seconds were up for about 1 to 2 minutes to let the test load cool down.:(

Well even by doing this i ended up burning up the SMD 1 ohm resistor that comes stock on my test load. So i purchased another one to replace it with. After this i still was have trouble with it getting to hot really quickly.

So what i decided to do was heatsink the Test Load and let me tell you it has solved all the problems.:wave: I heatsink the 6 diodes as well as the resistor that i got to replace the original SMD one. Iam waiting for a new one to come in the mail because before i heatsinked the test load and resistor i was using the new resistor with out it being heatsink that is why you see slight burn marks on the resistor. But it has not effected the test and is still reading 1 ohms. Once the new 1 ohm resistor comes in iam going to replace the slightly burnt color one in the video with the new one that is coming in.

So if you set alot of drivers over 1amp 1.5amp or 1.9amps etc or even just for personal DIY laser builds definitely give this a go. It does not effect the acutely output of the test. I made sure to check if the output was the same before and after heatsinking.:)

Check out this video i did to show you all how long it can be left on Running at 1770mA/1.77amps with no problem of over heating or smoking anything.:beer: I could have left it on longer but i dint want to bore you Guy's. :na:


Closer Pictures of the heatsinking it self. The smaller heatsink is detachable form the larger heatsinking by a screw to make it more portable like:
The new resistor should be in this week to replace the one you see in the picture. This was caused before heatsink the 6 diodes and resistor. You can also see i left enough room to be able to change between Re and Blu Mode.:)
678_1005.jpg


678_1006.jpg


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So If you want to do this mod Here are a little tips:

You Will Need:
Thermal Adhesive. It must be adhesive or it wont stick.
Link:
Amazon.com: Arctic Alumina Thermal Adhesive (Two Tube Set): Electronics

A vice or something that can hold the heatsink to the 6 diodes when the thermal adhesive is setting. "You can use your hands but depending on what adhesive you buy you could be holding it for a wail. The one i used from a friend sets in 5 minutes."

Your DIY Test Load or the Rkcstr version like i have."If you are using the Rkcstr one like i have you will need a through hole resistor as well as if your DIY test load is SMD you will also need a through hole resistor.":)
You can get a 1 ohm resistor at Digikey.com or any other place you like.


1)You will need to mix up the adhesive if it is a 2 part mix 50% A + 50% B.

2) Then apply enough to cover the 6 diodes.:)

3) After applying the thermal adhesive you will need to place the heatsink on top of the 6 diodes where you applied the thermal adhesive and then put it into a vice to set for about 10 min i would call safe if you re using the thermal adhesive that i used in the link above. If you are not using the same as the link above please fallow the direction on the back of your thermal adhesive and allow that amount of time for it to set."Note: if you are using the Rkcstr test/dummy load please take a look to where you place the heatsink and make sure you leave enough room to switch in between the Red and Blu setting on the test load."

4) Once that has set it is now time for you to mix up some more thermal adhesive to mount the resistor to the heatsink. The way i did is before soldering the resistor to the test load i formed it into the correct shape then i soldered it in place and took the thermal adhesive and applied it under the resistor with a tooth pic. Your DIY test load will be a different set up so just form the resistor to best fit your design of the test load.

5) Your Done.


Another tip i can say is if you have the Rkcstr test load you can look at the pictures above to see that i added 2 long strips of metal that i took from an old resistor and soldered them to the test load where you would hook up your DMM to. Makes things easier to use alligator clips then to try and use prongs to hold them in place and set the current.

Also i ran a black and red wire from the test load that would connect to my driver to make it also more easier to hook up when you re ready to set your current.

I hope this helps.:)


:thanks: For Looking .!!!
 





Why not make a parrellel-series resistor array? Four 1ohm resistors in 2X2 configuration (two series sets of two 1 ohm resistors in parralel) equals 1ohm but you get way more load capability. I set my microboost over 1A yesterday and the resistor array never even got warm.

Alternatively, you could use a lower ohm resistor of equal power so it will heat up less at a given load.

Although the diodes do probably need heatsinked over 1A... no way around that.
 
I guess you can also do this but when running a LM350 with 12volts the resistors are going to get hot regardless.

Plus the heatsink was right there in front of me so i said why not and i dint want to make it messy by adding 4 resistors to the setup. It was to tight of a space to fit all. But if you do a DIY Test load should be easier to do.:) Either way i would still heatsink them regardless after seeing the results of this test and trying to set a driver to 1.8amp and be able to run it for a long period of time was great. Test out to see if the heatsink for the LM was holding up good etc.

Iam working on a cool laser right now cant wait to finish it.:)
 
This looks like it is a great solution for you and I'm glad it worked well for ya. Like you said, you just happened to have the big ol' heatsink sitting right there in front of you.

So this pre-made test load you bought cost ~$11 from stontek assembled and ~$6 from rkcstr un-assembled. For $20, flaminpyro sells pre-assembled, potted, 3A test loads. http://laserpointerforums.com/f64/fs-laser-tools-44115.html

Personally, I'd just make my own for a whole lot cheaper. Just use the 1N54XX series diodes (rated up to 3A) and a 5W 1 Ohm resistor. :D
 
This looks like it is a great solution for you and I'm glad it worked well for ya. Like you said, you just happened to have the big ol' heatsink sitting right there in front of you.

So this pre-made test load you bought cost ~$11 from stontek assembled and ~$6 from rkcstr un-assembled. For $20, flaminpyro sells pre-assembled, potted, 3A test loads. http://laserpointerforums.com/f64/fs-laser-tools-44115.html

Personally, I'd just make my own for a whole lot cheaper. Just use the 1N54XX series diodes (rated up to 3A) and a 5W 1 Ohm resistor. :D

That was accutly going to be one of my next projects waiting for a good size digikey order to come in.:wave:

I figured i would post this for those that already have this test load or a DIY test load already Rated "1A". and they had a heatsink laying around and dint have the extra little money to make another test load.:D Iam going to just end up using this one for a Red test Load and the 3A Test load for the 405nm etc.
 
Why not just get some 1N5404 diodes and a 1Ohm 5W resistor..

Also, At high currents make sure to use less diodes. like 3-4 for blues.

Peace.
 
Why not just get some 1N5404 diodes and a 1Ohm 5W resistor..

Also, At high currents make sure to use less diodes. like 3-4 for blues.

Peace.

Why use fewer diodes for high power blues (1000+mW)?
Do blue diodes have a lower Vf at very high currents?
 
at high currents the diodes Vf does up and the resistor takes more. Wow I didn't see that :P
 
Also, At high currents make sure to use less diodes. like 3-4 for blues.

Why use fewer diodes for high power blues (1000+mW)?
Do blue diodes have a lower Vf at very high currents?

at high currents the diodes Vf does up and the resistor takes more. Wow I didn't see that :P

As far as I know, and someone with more electronic experience than me can correct me if I'm wrong, but this only applies to the 1N4XXX series diodes. They are rated at 1A. Before people started making test loads that can handle higher current, they were using the same old test loads we've always used. When running 1A of current through a 1N4XXX rectifier diode, the voltage drop increases to >0.9V so that is where he gets using 4 diodes for a 445nm.

The 1N5XXX series rectifier diodes are rated at 3A and should keep the voltage drop of 0.7V.
 
Interesting... I did not know this. Can V drop be verified on a rectifier diode by placing a voltmeter across the leads?

If you keep a 1N4XXX rectifier diode well cooled or put current through in short duty cycles will it still have a typical 0.7 Vf? (what I'm asking is if the heat causes the Vf to rise)
 
Interesting... I did not know this. Can V drop be verified on a rectifier diode by placing a voltmeter across the leads?

I would assume so. I've never actually done real world testing. I've just read the data sheet and this is also what drlava has said. (I'd have to do some searching to find his quote) :yh:

If you keep a 1N4XXX rectifier diode well cooled or put current through in short duty cycles will it still have a typical 0.7 Vf? (what I'm asking is if the heat causes the Vf to rise)

I don't think so. If you look at the graph on page 2 of the data sheet (top right graph), it states "Instantaneous forward current".

See here: http://www.diodes.com/datasheets/ds28002.pdf
 
Interesting... I did not know this. Can V drop be verified on a rectifier diode by placing a voltmeter across the leads?

Yes.

Also, keep in mind that for power diodes, the FV is not 0.7V, it's higher, and that the FV also increase with the current ..... some good high current diodes have usually FV values that go from 1 to 1.5V, with a medium value of 1.2V ..... the 0.7V is the standard FV value of a normal silicon diode junction under 100mA, usually .....


EDIT: as for the 1N4xxx serie, it's the same thing ..... it's around 0.7V for low currents only ;)
 
Thanks for clarifying that HIMNL9, I was under the impression that my DIY test load was absorbing too many volts. However, to test it I was running it off a 9v battery(said battery was tested at 8.9v), whereas it is intended to test a ~110mA current. Saved me a couple hours of head scratching :)
 
Yeah, I used 1N5404 diodes and 4 .5ohm resistors (1W). 2 parralel, 2 series. I also used a bunch of the jumpers you see on the back of hard drives so I could select how many diodes are in the circuit.
I have run it for around 2 minutes I think and some of my drivers are going up to 1.5A. So far, no heat issues.
I wouldn't stick it down my pants after a test but the components can handle a LOT of heat.
 
Here is mine I use 3A diodes and 4x 4 ohm wire wound resistors in parallel. You could also use a smaller resistor like a .1 ohm and do some slight math

2010-11-30_19-47-03_752.jpg
 





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