Spoke POV with LiPo Battery... Waterproofed and Secure (I hope!)

by dt1000 on Wed Apr 20, 2011 11:16 am

I finally finished my SpokePOVs and they work great!!!
I did a few things differently for my install that (IMHO) improves the overall package...

Image

LiPo Battery
Each SpokePOV is drawing its power from a LiPo Battery.
These are 1/3 the weight of the standard AAs (based on using three of them).
Also, they are rechargable, and keep their juice for ages.
They plug into the board via a little connector soldered to the board at J1.
These are attached to the board with velcro pads and a cable tie through the holes for the AA battery clips.
I wanted to go with just velcro, so I could pop the batteries off for recharging, but it didn't feel secure enough.

Waterproofing
I applied several coats of Silicone Conformal coating to seal the board, and checked it with a UV lamp.
Hopefully this should be OK to protect my SpokePOVs from Vancouver's not-so-dry climate.
I also covered the LiPo Batteries in heat-shrink tubing and closed-off the ends with silicone sealant (the stuff you'd use for a bathroom).
Where the LiPos plug into the board, I made a little jacket out of heat-shrink that slides over the connector (I can post more pictures if anyone is interested).
Finally, I bought connectors to cover the I/O ports and plugged any gaps in them with the sealant.

Security
After all that work, I didn't want my SpokePOVs nicked, so I tried my best to make it difficult for them to be removed.
At the top connector, where the spoke is a little fatter, I bolted the SpokePOV to the wheel with a nylon cable clamp.
Then, at two of the other connections I used metal wire and threaded it around the spoke using a technique similar to one I found via the Monkelectric website.
Now thieves will at least need a screwdriver, scissors, pliers and a lot more time to relieve me of my goods.
Let's hope they don't just decide to cut my spokes...

Also...
I found some cool, curved, rare-earth magnets at my local electronics shop that fit beautifully around my bike's frame.
I still had to double them up to get the Spoke POVs to fire reliably though...

All the extra ingredients above should be readily available at your local hardware and electronics stores.
Feel free to ping me if you have any questions.
:)
Dan
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Re: Spoke POV with LiPo Battery... Waterproofed and Secure (I hope!)

by adafruit on Sun Apr 24, 2011 10:56 am

nice work!
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Re: Spoke POV with LiPo Battery... Waterproofed and Secure (I hope!)

by JosieNutter on Thu Sep 22, 2011 2:00 pm

How has the waterproofing worked out? I'm thinking about doing the same thing for some a bit south in rainy Seattle. :)
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Re: Spoke POV with LiPo Battery... Waterproofed and Secure (I hope!)

by thejukeboxer21 on Mon Dec 12, 2011 6:24 pm

Just want to make sure, but that lipo battery in the link provides enough voltage for the blue leds? It says it varies from 3.7 to 4.2 volts, seems like less than 3 AAs? And does it come with the connector needed to attach to board at j1? Also what silicone coating could you recommend, I haven't found one in a store yet and will likely try to buy online.
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Re: Spoke POV with LiPo Battery... Waterproofed and Secure (I hope!)

by adafruit on Mon Dec 12, 2011 10:15 pm

a lipo is about 3.7 for most of its life == 3 AA rechargables
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Re: Spoke POV with LiPo Battery... Waterproofed and Secure (I hope!)

by thejukeboxer21 on Sat Jan 14, 2012 10:12 pm

Alright, so after much searching I found the best deal in cost and shipping on the JST board connectors through Digikey, I thought I would share the links for anyone else that is searching. They have both straight and right angle connectors. I've tried them and they connect properly to board and to the battery leads. Digikey part #s: 455-1704-ND and 455-1719-ND. Links: http://search.digikey.com/us/en/product ... -ND/926611 and http://search.digikey.com/us/en/product ... -ND/926626
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Re: Spoke POV with LiPo Battery... Waterproofed and Secure (I hope!)

by circuitmonkey on Tue Mar 06, 2012 7:25 pm

I apologize in advance for "newbie" questions.

Per this forum, I really like the idea of substituting the onboard 2xAA cells with the LiPo battery pack or another offboard battery pack. Thanks for a great idea.

For water proofing and weight considerations, I won't be using silicone conformal and instead will substitute a thin layer of optically clear epoxy on both sides of the board with a 2.1mm barrel connector pigtail dongle at J1 for power.

If I use the 2700mAh LiPo battery, could I power three of the SpokePOV units connected in parallel? How does one even calculate this sort of thing?

For instance:
-The LiPo battery output is 3.7-4.2volts. Isn't that too much for the SpokePOV unit (it only takes 2x1.5v AA cells)? Does this mean I can use this battery pack as a power source: http://www.sparkfun.com/products/10110 (3x1.5v AA cells)?


-Alternatively, if I hook up three SpokePOV units, each consuming 3.7v, to a 2.7Ah LiPo, then is the calculation 10Wh/(3*3.7v)=0.9Ah? So this battery will provide 54minutes of running time? If it consumes 3v exactly, I'll actually get about 66 minutes of running time. Will battery discharge and heat be a problem?

Anyways, thanks in advance for the help.
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Re: Spoke POV with LiPo Battery... Waterproofed and Secure (I hope!)

by adafruit on Wed Mar 07, 2012 10:32 am

it COMPLETELY depends on how many LEDs are lit at a time. each LED draws about 10mA
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Re: Spoke POV with LiPo Battery... Waterproofed and Secure (I hope!)

by SamDecrock on Mon Dec 03, 2012 5:11 am

Hi,

I want to ask the same question as the poster above:

Is 3.7V not to much as the spokePOV only takes 2 batteries for red LED's?
2 batteries = 2x 1.5V = 3V ==> 3V < 3.7V

Sam
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