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  • Author Author: genebren
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Walky the Biped Robot - A new hope (actually a new body and battery)

genebren
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Previous post in the sequence:

Walky the Biped Robot - The prequel

Walky the Biped Robot - Power pack

Walky the Biped Robot - Oops, Walky has an accident!

 

Walky is not quite ready to walk, but still moving in the right direction.  I have redesigned the main body of Walky, opting for a two piece structure. While I had Fusion360 open, I also designed new feet, legs and accessory mounts that I will be printing over the next few days.

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Here is are multiple views of the body with power pack and servos installed.  The parting line between the two halves is barely visible (first image) and the recessed holes for the joining screws worked out wonderfully (second and third images). That shiny red battery is new too. Earlier testing of UltraFire (not!) batteries was disappointing.  These batteries over promised and under delivered, yielding a capacity around 250-350mAh as opposed to their advertised capacity of 1200mAh.  The new Panasonic batteries (UR14500P) did not disappoint.  Here are the results from the first charge/discharge test:

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In both tests, the accumulated capacity calculations were extremely close to the advertised capacity, most likely varying only due to forced discharge stop of 2.7Volts.  Now we are cooking!  With a steady state load of 500mA on the 5Volt boost supply, this battery will give me over an hour of play time with Walky (although I expect that in normal operation the load will be less that 500mA).  The charge rate is conservative, at ~.6C, while taking ~2.5 hours.  The discharge rate varied from ~.8C to ~1.2C throughout the test, while lasting ~70minutes. Once again, thanks for the great battery recommendation!

 

Thanks for reading along. Hopefully, with a bit of 3D printing time I hope to have Walky back on his new feet soon!

Gene

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