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ArcticMyst Security by Avery

Help on the Micro Boost drive

Joined
Sep 12, 2007
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I question the connection at the top left and possibly bottom right here. It's supposed to be through-hole, isn't it? Are you sure it's making contact with the other side of the board as well?

30754d1291601218-help-micro-boost-drive-microboost-c.jpg
 





Joined
Feb 7, 2010
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I am sure there is contact and continuity of the circuit. I am uncertain how good it is though. I assume you are talking about the top right and the bottom right where the through holes do not have wires poking through them. It is definitely meant for through hole connection. I assumed it would be good enough to solder to the top for temporary testing based on my previous experience but maybe that has led me to a bad way of testing things. It is hard to see the connection on the other side because the wires are so much bigger than the hole which makes me believe I should always put the wire through even for testing to make sure there is a good connection.

I will go ahead and re-solder them with the wire going through just to rule that out if I can not find the problem with my DMM. (1) Before that I will also check to see if there is a voltage drop across the connection when under power. That should tell me if the connection is bad from what I understand about electronics work. I am no electronics expert... no official training in it except 25 years ago in middle school. Most of what I know on the subject is mainly from reading over the years and experimentation.

I just realized I don't have another 445nm diode right now. I only have the 12x 405nm diodes left and a 6x 405nm. The driver according to the test load starts out about 650mA and then constantly increases every second so I wouldn't want to risk the diodes.

I want to use this as a learning experience for troubleshooting circuit problems so I am reading up on the net as much as I can on troubleshooting circuits when I can. Ideally I should be able to find the problem with my DMM. I don't want to change anything until I can find the problem (unless it takes too long of course).

I just recently got a Fluke 289 that has logging and graphing on the LCD and accurate to 0.025% on the voltage side. My previous DMM was a cheap tiny pocket DMM from radio shack that I bought when in high school. Amazingly I tested it and it is within around 4ma from the Fluke. I figured it would be much worse considering it was cheap and is so old but maybe it is still way off at more of the extreme limits of the DMM.
 
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I have a theory to test out. The rkcstr dummy load on the red setting is a pretty low voltage drop. I know that it worked when I used a microboost at the max range setting. The past 2 microboost drivers that exhibited the regulation problem on me (I only posted one of them in this thread) in this thread were both set to lower ranges (the same as the original poster and he used the red setting too). I wonder if the dummy load voltage drop being so low on red settings when used with a 4.2v battery is too much input voltage and causing this odd behavior even though it seems to work ok on the higher range driver setting.

I will test this tonight by changing the dummy load to the blu-ray setting and see if it starts working. If it does then I will change it back to the red setting and see if the problem repeats itself. I have high hopes that this is the problem because I just don't see any problems with the circuit.

I tested for a voltage drop around the soldering connections that I did under load and there is none which seems to indicate that the connections are good. I already know that the connections are good as far as continuity and resistance(for example with a bad solder joint).
 
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Triple post for the win!

It works! I was right. The pot works and the current is stable when setting the dummy load to the blu-ray setting with a 4.2v input and the driver on the mid range setting. The problem seems to be that the 4.2v input voltage is too high with the rkcstr dummy load on the red setting when using the microboost at the lower range settings. If I put the rkcstr back to the red setting I get the problem behavior again (pot doesn't change anything and the current slowly increases).

My guess the reason it works at the higher driver range setting is that I was pulling 1000ma+ at the higher current range setting which causes the voltage to sag more than when I set the driver range lower and only pull 500 - 650ma. That extra voltage sag of the battery at the higher output draw brought the voltage low enough to work.
 
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