Jstr
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- Feb 10, 2014
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Hi y'all, so I've been trying to set my driver (Blitzlinear) to 790 mA for a BDR-209 build, but something doesn't add up with my test load. After I attached leads and connected it to a pair of 16340 batteries, I get my 790 mA using the usual 6 diodes in series (dropout should be ~6.8 V at that current according to ARG's graph). But then I had a genius inspiration to use the ohmmeter to measure the actual resistance of the "1 Ohm" resistor, and turns out it is actually 1.4 Ohms. I confirmed this with two different multimeters. So using the voltage drop across the resistor (.79 V), the current should actually be closer to 564 mA, a huge difference. Here's the weird part: when I connect the ammeter in series with the test load, I get 810 mA, an increase rather than the expected decrease in current, which makes absolutely no sense. Which should I trust? 564, 790, or 810 mA?
Here's some additional information about my experience with this test load because I have used this load for a while without checking the resistance.
This will be my second time using this diode (same driver, same current). That diode got :gun: (because I underestimated the heat output of this driver and ran it too long). One thing to support the current actually being ~564 mA is the power output of the last diode was just under one Watt (with G-2), which fits the power curve much better, albeit on the efficient side. I would expect around 1.2 Watts at 790 mA.
I have measured the current of several constant current x-drives, which I have used. Two were spot on 1.8A with the test load but I think I only got about 1.8W with one m140 and for the other, I got 2.3W from an m462. Then I measured a CC-boost at 1.79A and that gave me a pretty incredible 2.4W from an m140, but here this was a boost and the reading was with 4 diodes on my load, a 5.4V load compared to a 4.5V actual load, so current may actually have been higher once I attached the LD. But then there were some 2.4A x-drives that measured below spec, three at 2.15-2.16A and those gave me 2.65W, 2.68W, and 2.7W.
One more thing, the driver gets extremely hot quickly. Without a heatsink, thermal protection kicks in after ten seconds. If it is only 564 mA, that heat is somewhat unbelievable.
I would normally want to trust the math and Ohm's Law, but the ammeter in series reading higher really bothers me. Also, that would mean my x-drives were very under spec (1.54A from 2.4A drivers, and then my diodes were way underdriven and impossibly efficient).
Thanks for reading and any input would be great.
I used a Radiant x4 LPM and the same G-2 lens for all power tests. Also just want to add, I have had no problems with the driver.
Here's some additional information about my experience with this test load because I have used this load for a while without checking the resistance.
This will be my second time using this diode (same driver, same current). That diode got :gun: (because I underestimated the heat output of this driver and ran it too long). One thing to support the current actually being ~564 mA is the power output of the last diode was just under one Watt (with G-2), which fits the power curve much better, albeit on the efficient side. I would expect around 1.2 Watts at 790 mA.
I have measured the current of several constant current x-drives, which I have used. Two were spot on 1.8A with the test load but I think I only got about 1.8W with one m140 and for the other, I got 2.3W from an m462. Then I measured a CC-boost at 1.79A and that gave me a pretty incredible 2.4W from an m140, but here this was a boost and the reading was with 4 diodes on my load, a 5.4V load compared to a 4.5V actual load, so current may actually have been higher once I attached the LD. But then there were some 2.4A x-drives that measured below spec, three at 2.15-2.16A and those gave me 2.65W, 2.68W, and 2.7W.
One more thing, the driver gets extremely hot quickly. Without a heatsink, thermal protection kicks in after ten seconds. If it is only 564 mA, that heat is somewhat unbelievable.
I would normally want to trust the math and Ohm's Law, but the ammeter in series reading higher really bothers me. Also, that would mean my x-drives were very under spec (1.54A from 2.4A drivers, and then my diodes were way underdriven and impossibly efficient).
Thanks for reading and any input would be great.
I used a Radiant x4 LPM and the same G-2 lens for all power tests. Also just want to add, I have had no problems with the driver.
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