Computer, Red Alert!

A project log for DSKorder

A handheld interface from the future or past.

XasinXasin 07/06/2019 at 10:212 Comments

Gha ...
I've already written this as a comment on Jan's project about his blown-up LDO, about how I've been struggling with a similar problem, but I wanted to post a project log update as well.

During recent, normal operation, I had the pleasure of hearing a sudden "pop" somewhere inside the casing. Now, as far as I know, that's not part of what these chips are supposed to do, and when you smell magic smoke, something is definitely broken.

In order to prevent even more from breaking, I had to take the casing apart as quickly as possible, and cut the wire of the LiPo, as parts of the charge circuit were connected directly to the battery, with no switch in between.

Cracked screens and broken emotions
During the rushed unscrewing of the caps, I broke the OLED Screen wire. Be real careful when handling these!
The LiPo wire's ground was cut, preventing further damage and discharge. It has buit-in short-circuit protection, but ... Take no chances!

During "post-op", I managed to get a closer look at what had happened. There are no visual marks or popped ICs, but I am very sure the charge IC, a MCP73832T, is at fault, because the "charging" LED had been glowing with no cable plugged in. In fact, this is the same chip that failed on my Lasertag project!

Although I might not have added aaaaalll  the smoothing capacitors, there was a 10uF on the input and output side, so I am definitely going to look for a beefier IC.

As for the DSKorder itself, I was able to desolder the broken IC and power the circuit via USB. Nothing else was damaged, and even the USB-To-UART chip, which is powered from the same line as the Charge IC, responded just fine.
I'll replace the broken IC with an external 500mA charge board, so ... All's well! 

Just need a better charge IC for next time.


Dylan Brophy wrote 07/29/2019 at 16:38 point

Aww man, that's too bad.  Guess that MCP73832T isn't good enough :/  The Sparkfun ESP32 Thing uses an MCP73831 (looked it up because the chip on the Thing feels hot when charging), and I think my board actually has had the magic smoke too.  Somehow the charging circuit still works??  I think we all need beefier chargers though XD

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Xasin wrote 07/29/2019 at 16:50 point

Or just be a bit more careful and reduce the charge current. I've since removed the faulty chip and somehow managed to solder in a charge circuit, so it's all good for now.

The next Lasertag revision will also try out a charge IC from a different brand, and I'll probably reduce the current to something more comfortable.

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