Monthly Archives: October 2013

Fast response robot hand

This is pretty cool. I wonder if this kind of predictive processing is possible on a mobile basis, or if the computing needs to be offloaded to a desktop.

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2013-10-28 · 00:51

Battery & charger soldering adventure

Today I did some more soldering with the TP4056 linear charger board and the 240mAh lipo battery pack.

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Tinned the PCB and all wire prior to joining up and making the final joint. Solder joints were between stripped leads of a USB cable through the PCB’s VCC holes, and solid 22AWG wire to the battery’s stranded leads.

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The lack of tools to hold the subject, together with the lack of constant heat from my soldering iron, made for a few extra challenges. Nevertheless, I was able to get satisfactory results.
ScreenClipxxxxPlugging in the board and testing the charge voltage, I was able to seemingly trip the TP4056 into a charge cycle. I’m at a loss as to why my meter is registering a float voltage above the data sheet’s maximum of 4.263V. My initial assumption is that IBAT refers to the rating of the cell to be charged, I may be mistaken.

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Referring to the data sheet for the TP4056, the stock RPROG at 1.2K ohm will not provide the proper charge current for my 240mAh cell.  According to the chart, a 5K ohm RPROG will limit charge current to a 250mAh cell. The closest and easiest match without going under is 5.1K. Now I just need to get my hot little hands on these resistors. While I still have them, of course. Fingers crossed nothing explodes on the first charge cycle. Definitely will be observing all safety precautions and charge in a fire-safe location.

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After more reading in preparing this post, it seems as though this battery is not suitable for the cat tracker project. Given the lower discharge rate (1.5C), a safer option for powering my cat tracker could be the rechargeable lithium 16340/CR123A. These cells can be charged safely with the TP4056, pack more of a charge at ~880mAh per cell, and are the perfect form factor for smaller projects. The 20C lipo will be more useful for a future project.
Now, to source a 16340. Any leads? 😉

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Filed under Battery power, DIY, Soldering