Help with battery power options

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samuelguyer
 
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Help with battery power options

Post by samuelguyer »

Hello all,

I have been working on a project that uses a 5V Arduino micro, a pushbutton, and a small strip of neopixels. I'd like to power it using rechargeable batteries, but I'm not sure how to get the right voltage, since the Lipo batteries are all 3.7V. It seems like my options are:

(a) Redo the project with 3.3V Arduino (boooo)
(b) Connect multiple batteries to get a higher voltage (how? is that safe?)
(c) Somehow step up the voltage

One idea I'm tinkering with involves cannibalizing one of those back-up batteries for phones. I bought one and tore it apart -- it has a 2600mA Lithium battery with two USB connectors (one for input and one for output) attached to some charging circuitry. The nice thing is that it outputs 5V. The only problem with this arrangement is that it's not easy to add an on-off switch, since the USB out goes directly into the Arduino USB micro.

Any help or ideas is greatly appreciated!
Thanks!

One other related issue: I am using a capacitive touch sensor as a button (one of these: http://www.adafruit.com/products/1374), but I've noticed that when the LEDs are flashing, the touch sensor starts freaking out and randomly thinking it is being pushed. This problem only seems to happen when I'm using battery power, not when I'm using USB power from my computer. I'm not sure what's going on, but it makes the project unusable.

-Sam

waltr
 
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Re: Help with battery power options

Post by waltr »

Look at the Minty Booster that Adafruit sells.

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samuelguyer
 
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Re: Help with battery power options

Post by samuelguyer »

Thanks. That looks interesting, although it doesn't look like it can handle the recharging. I want to create a self-contained unit that can be recharged by just plugging a USB cord into a laptop or one of those charging "cubes".

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adafruit_support_bill
 
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Re: Help with battery power options

Post by adafruit_support_bill »

I want to create a self-contained unit that can be recharged by just plugging a USB cord into a laptop or one of those charging "cubes".
A MintyBoost, one of our LiPo Chargers and a LiPo Cell (instead of the 2xAA cell holder) will do all of that.

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samuelguyer
 
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Re: Help with battery power options

Post by samuelguyer »

Great, thanks!

Just so I'm clear: I plug the JST connector from the battery into "battery" input on the charger, connect the "load" output from the charger to the input on the MintyBoost, then connect the output of the MintyBoost to the Arduino.

I should probably put the on/off switch on the charger-to-MintyBoost connection, so I can charge the battery without turning the device on (duh).

I could also connect the output of the MintyBoost directly to the 5V/ground pins on the Arduino, right? I don't need a whole USB cable. Would I be better off buying the components for the MintyBoost separately (since I don't need the USB output or the batter holder)?

Space is fairly tight in my project, so if I can eliminate a fat USB connector and cable, that would help.

Thanks for your help!

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samuelguyer
 
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Re: Help with battery power options

Post by samuelguyer »

It occurs to me that this kind of setup might be really common, given all the 5V microcontrollers out there. It would be nice to have a version of the USB lion/lipoly charger that included the voltage converter circuit to output 5V. How hard would it be to build something like that myself?

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michaelmeissner
 
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Re: Help with battery power options

Post by michaelmeissner »

You mentioned about not having an on/off switch for USB. Adafruit recently added a USB cable with an on/off switch: http://www.adafruit.com/products/1620. They also offer DIY USB connectors, so you could make your own cable with your own switch.

Or you can get phone battery chargers that have an on/off switch on them. I picked this up a few years ago, and it will run an Arduino Uno for about 4 days running blink: http://www.amazon.com/EZOPower-5000mAh- ... er+5000mah. Adafruit now carries similar batteries for running Rasberry Pi, but there was a discussion a few months ago, that some of these will go to sleep if the microprocessor doesn't use enough charge.

In theory you do do what you want with just Adafruit products: In some of the Gemma/Trinket tutorials, it mentions some of the neopixels can be run off of a lipo battery (3.7v) as long as you don't use too many pixels or make them too bright. The 16-led rings are one such neopixel that can be run with reduced power, but I think the meter strips can't. It would be nice if there was a table for all of the neopixel products (that was updated each time Adafruit produces yet another version) and gives the voltage levels, rather than having to go to each data page.

I've run a Gemma (3.3v) off of a 1200 maH lipo battery driving 2 neopixel 16-led rings in my steampunk goggles. I don't tend to run the brightness more than 30 (out of 255). When I did my test, the Gemma lastest between 24 hours and 36 hours with the 1200 maH lipo battery, which means in my circuit, I am using between 33maH and 50maH.

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samuelguyer
 
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Re: Help with battery power options

Post by samuelguyer »

Thanks for the suggestions. I will either build it using Adafruit products (as you described), or use one of those battery chargers (I bought a couple different models already).

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adafruit_support_bill
 
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Re: Help with battery power options

Post by adafruit_support_bill »

Just so I'm clear: I plug the JST connector from the battery into "battery" input on the charger, connect the "load" output from the charger to the input on the MintyBoost, then connect the output of the MintyBoost to the Arduino.
Correct.
How hard would it be to build something like that myself?
We do publish the board-files for these if you want to try that. See the product tutorials for links.

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michaelmeissner
 
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Re: Help with battery power options

Post by michaelmeissner »

Speaking of the Adafruit lipo chargers that allow the battery to be charged and power the load at the same time (such as the USB/DC Lithium Polymer battery charger), I always thought the power out should have had the JST male connector instead of the female connector, so that you could either connect the board directly to the battery, or connect it to the charger board. As it is now, you need a little shim cable that converts JST female to JST male.

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samuelguyer
 
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Re: Help with battery power options

Post by samuelguyer »

OK, I went ahead and ordered the battery/charger/MintyBoost set (not inexpensive, by the way). I'll try that, and I'll try fiddling with the "Phone backup battery" thing (that is inexpensive!).

Thanks Michael and adafuit_support_bill!

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564mumble
 
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Re: Help with battery power options

Post by 564mumble »

i need help with the assembly of the simple balanced charger for the USB/DC LiPo Charger. i have the 3-pole double throw switch. but i have no idea where to solder the wires. any help? thank you

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adafruit_support_bill
 
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Re: Help with battery power options

Post by adafruit_support_bill »

i have the 3-pole double throw switch. but i have no idea where to solder the wires. any help? thank you
On the diagram, you will see that there are 3 wires connected to the right side and 6 wires that connect from the left.

The three connections on the right side of the diagram go to the common terminals on your switch. On most switches this will be the center row of terminals.

For the connections coming from the left side in the diagram, half connect to the upper position of the switch and half connect to the lower position of the switch. On your 3PDT switch, there should be a row of 3 terminals above the common row and a row of terminals below the common row.

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