Requesting input on Trinket and Bluefruit project idea

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lowena
 
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Requesting input on Trinket and Bluefruit project idea

Post by lowena »

So I have a project idea involving a Trinket and Bluefruit to provide wireless serial communication for an already-existing consumer product. It is to provide a Bluetooth link between an Arduino/Android device/computer and my TI-84+ calculator. I thought it would be relatively simple and fun to do as my first "serious" project. I've tinkered and messed around with things before, but only using breadboards to learn how to do things, nothing permanent and no actual "product".

All this thing would do is take packet information over Bluetooth from whatever it's paired with and relay it to the link port of the calculator, so the electronics and code don't need to be complex. KermMartian of the Cemetech forum has already written a couple routines for Arduinos that use the TI calculators' native protocol, so you can control pretty much the entire calculator remotely. Add wireless to it and I think it would be pretty cool. Also, I have a thing for modifying consumer devices... 8)

Here is an extremely simple, totally not-to-scale mockup:

Image

The Trinket and Bluefruit would be enclosed in some sort of case, and will require a battery. It seems that the Bluefruit is 5v, but Adafruit doesn't have any 5v Lipo packs, so I am unsure what to do about that. I could possibly step up the voltage to 5v (maybe?). I would like to put a Lipo battery in that could be charged inline, that is not having to take it out of the case and plug it into a charger. I am not really sure how to do that either.

The plug would be a standard 2.5mm male audio TRS plug. The space between the box and the tip needs to be at least 20mm, which shouldn't be a problem. Mouser has plain plugs you can buy, and I was just thinking of cutting a hole in the box and soldering wires from the plug to the Trinket. I have no idea yet what I'll use for the case. I could use some pre-built plastic box, but would prefer 3D printing something or doing something laser-cut.

Of course the case would have an On/Off switch and somewhere to plug a cable (probably USB) to charge the battery, and the battery would be insulated from the other components. One thought, though, would a Lipo battery generate too much heat to be enclosed like that?

TL;DR
1) What kind of rechargeable battery pack could I use to power a Bluefruit and Trinket that also wouldn't overheat anything?
2) How can I make it so that the battery pack can be recharged without being unplugged from the Trinket?

Thank you anyone that can help! :)

(Sorry if this is disjointed, that's my brain's fault. And sorry if at any point I sound like I know what I'm doing; I don't. :mrgreen: )

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adafruit_support_rick
 
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Re: Requesting input on Trinket and Bluefruit project idea

Post by adafruit_support_rick »

1) Use a LiPo and connect it directly to the EZ-Link.
2) Power a 3.3V Trinket from the 3.3V output of the EZ-Link (connect to the 3V pin on the Trinket)
3) Use this charger: http://www.adafruit.com/products/259
4) Use any size LiPo battery you want - bigger batteries have longer run times. There's no difference in heat.
http://www.adafruit.com/index.php?main_ ... ly+battery

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lowena
 
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Re: Requesting input on Trinket and Bluefruit project idea

Post by lowena »

Thank you very much, Rick! I assume you plug the battery into the charger, then from the charger to the EZ-Link? Does the charger start charging the batter automatically, or is there some way you have to tell it to charge instead of having the battery just powering the EZ-Link and Trinket?

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adafruit_support_rick
 
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Re: Requesting input on Trinket and Bluefruit project idea

Post by adafruit_support_rick »

lowena wrote:I assume you plug the battery into the charger, then from the charger to the EZ-Link?
Correct.
lowena wrote:Does the charger start charging the batter automatically, or is there some way you have to tell it to charge instead of having the battery just powering the EZ-Link and Trinket?
It should handle that automatically. It powers the EZ-Link in parallel with charging the battery.

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