EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: bumba000 on October 15, 2015, 07:52:22 pm
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I have a few of these so called lipoly backpacks here for my pro trinkets. I wanted to remove the LED/Diodes from the backpacks, so I did. Now the backpack doesn't charge the battery. So I spent a lot of time studying the schematic and the chip's datasheet yesterday. Then watched Dave's lipo charger video which is what actually helped the most.
I wanted to remove the leds and also have a way of using the trinket / arduino to detect when a usb cable is attached. I have the usb detect part figured out. What I'm having some trouble with is why can't I remove the led diodes? What will I have to do to get them out of the circuit but leave the circuit functional?
https://learn.adafruit.com/system/assets/assets/000/019/692/original/adafruit_products_schem.png?1410888704 (https://learn.adafruit.com/system/assets/assets/000/019/692/original/adafruit_products_schem.png?1410888704)
http://www.adafruit.com/datasheets/MCP73831.pdf (http://www.adafruit.com/datasheets/MCP73831.pdf)
Please and Thank You, John
EDIT** I guess I can simply replace them with a shottky??
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It seems as though I would like to replace the LEDs with silicone diodes as opposed to shottky diodes. Now I just need to know which size of silicone diodes to use. I have a couple here that are pretty small in size and values but what I'm working on is all surface mount and my silicone diodes are all through hole. So I will need to purchase some new surface mount silicone diodes, but there again I will need to know which value size would be appropriate for the schematic I've linked to above.
Thank You, John
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If you just don't want to see them why not just cover them with a small amount of black silicone?
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The STAT pin on the MCP73831 is an output and doesn't need to be connected. Removing the Charge and Done LEDs should not prevent operation of the charger, so I would re-check the charger CPB to see if you damaged something else whilst removing them.
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no. not silicone. thank you though. As for the stat not being required for operation: I can see from the schematic that what you're saying is true and also from what I think I understand from the MCP73831 datasheet. However. Removing the LED seems to make the charging stop. There is a chance though that I've damaged something while removing them. I still have a few left. Maybe I'll try another. I am gently with a very small razor removing the solder until the led comes free. No heat no prying. Just gentle cut strokes. Charge seems to stop. I'll try again...
Thank You.
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Post a photograph of your board showing your work.
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I figured out the problem. I will post a photo in a bit. my cellphone is my camera and it's dead at the moment. (funny I need to charge it too).
Ok. The first one that didn't work without LEDs didn't work because I messed it up by shorting it out with a DMM probe the day I got them. The second one didn't work because I had apparently destroyed a trace that is important to the circuit. Under a magnifying glass I was able to see that the trace was blown like a fuse. I know when this happened. It was when I was moving my project from bench to desk and the pwm lead from the arduino struck the ground pin. I recall hearing a tiny pop sound but nothing seemed to have gone wrong. Later on I removed the LEDs and noticed that the battery was no longer charging.
Very sorry for the confusion guys and I do appreciate all the input. I did fix the "blown" trace with a short piece of 34AWG mag wire and will post a pic shortly. Since I've been typing (and i'm pretty quick) my batteries gone from 3.56 up to 3.62. Thank you.
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Here ya go. The green line is where I repaired the trace using mag wire. Not sure why it looks like I added some kind of socket there. I did not. In person with a magnifying glass it looks great. I promise.
The green arrows point to where the LEDs used to be and the Red arrow points to the STAT leg of the MCP73831 chip. I have the STAT leg attached to my pro trinket. A couple lines of code and I can see when the usb cable is attached. A bit more code and I'll see if it's charging or maintaining.
(http://i.imgur.com/vdd7s09.jpg)