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MCP73831 indication LED troubleshoot
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MCP73831 indication LED troubleshoot

by unknown5591 on Wed Feb 15, 2017 4:48 pm

Hey all,

I've been working on a circuit for quite some time and have been coming across some issues. Initially I built the entire circuit using the IC's you'd find in a trinket and a trinket backpack. i.e. ATtiny85, MIC5225 and MCP73831. I kept running into problems with the complete assemble, so I figured it would make sense to isolate the parts.

Thus far I have got the programmed ATtiny to execute its commands.. which I'm pretty happy about. Unfortunately I am still running into trouble with the MCP73831 circuit which is modeled after the trinket pro backpack. When testing the circuit on a breadboard both LED's light up. While the red, charging LED burns bright the green, done LED is pretty faint. It remains this way no matter how long a battery is plugged in to the device.

My initial thought was that perhaps the components were to fair apart and it would serve me well to test them on a PCB. The issue now is neither LED turns on when plugged in. The only time I receive any LED feedback is when I connect a multimeter to the positive and negative ends of the red LED. In this instance the green LED turns on.

I've checked for shorts and cant seem to find any and even when as far as to build and test additional boards with no luck.

From what I can tell the IC might be functioning properly given the mutlimeter readings but the indication lights don't seem to be working properly. What could be the cause and why do I get such differing results from the breadboard to PCB? Is static shock really something I ought to concern myself with? I cant seem to figure it out considering the circuit is near identical to the backpack, minus the 2.5K resistor and jumper.


Looking at the data sheet I'm going to try testing the typical application of the MCP73831 on a breadboard and depending on if that possibly a PCB.

R1 and R2 - 1K
R3 - 10k
C1 and C2 - 10uF
LED1 - RED
LED2 -GREEN

Any thoughts?
Thanks,
-J
Attachments
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unknown5591
 
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Re: MCP73831 indication LED troubleshoot

by adafruit_support_mike on Thu Feb 16, 2017 12:19 am

Having both LEDs lit is a sign that the MCP73831's STAT pin is in a high-impedance state, which means the charger is either in a shutdown state or it doesn't recognize a LiPo being present.

Having both LEDs shut off is a sign that the voltage between the top of the red LED and the bottom of the green one is too low for both to light at the same time. With 2k of resistance between them, you'd need at least 4.5v to 4.8v for 1mA to flow through both.

Low supply voltage would also put the charger into shutdown mode. The input voltage has to be at least 150mV higher than the LiPo voltage for a charging cycle to continue.

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Re: MCP73831 indication LED troubleshoot

by unknown5591 on Thu Feb 16, 2017 10:15 am

Hey Mike,

Thanks for the reply, the supply voltage is coming from a wall outlet. It is connected to a micro USB breakout on a breadboard. The 5V supply and GND are connected to the Vin and GND pins on the MCP73831 breakout.

I've tried this with the adafruit trinket backpack and it manages to work just fine. The red LED lights when charging and green when finished.

As of now when trying the typical application of th MCP73831 on the breadboard with the single LED no light turned on. Going to check its connections.

Thanks again,
-Jesse

unknown5591
 
Posts: 65
Joined: Mon Jun 13, 2016 8:19 pm

Re: MCP73831 indication LED troubleshoot

by unknown5591 on Thu Feb 16, 2017 11:36 am

The three attached images have all three variations of the MCP73831 backpack I've been working with, i.e. Adafruit backpack, breadboard backpack, homemade backpack.

The adafruit and breadboard seem to be operating in a similar manner with a high red and dim green at the moment. I will leave this setup plugged in for a few hours and see what the results yeild. From experience I've seen the adafruit backpack go green high red off. Yet to see about the breadboard backpack, perhaps it wasn't plugged in long enough last time.

The homemade version shows no indication but the multimeter reads 4.1V into the battery. With a multimeter connected to the anode side of the green LED and the anode side of the red or the bat pin green goes high.

Any thoughts?
Could the homemade be imporperly connected? After all I'm pretty sure I've made the same connections but perhaps I'm mistaken.
-J
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Re: MCP73831 indication LED troubleshoot

by unknown5591 on Fri Feb 17, 2017 2:03 pm

Updated: I figured out the issue. I ordere the wrong part, MCP78311. Unfortunately this chip does not have indication lighting, although functions in a very similar manner.

-Jesse

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Re: MCP73831 indication LED troubleshoot

by adafruit_support_mike on Sat Feb 18, 2017 12:39 am

Ah, that would do it. Glad to hear you found out what was going wrong!

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Please be positive and constructive with your questions and comments.