3.7V LiPo -> 5V Trinket, Camera LED Ring

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monkeym
 
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3.7V LiPo -> 5V Trinket, Camera LED Ring

Post by monkeym »

Thanks to Noé & Pedro for the great write up about Camera LED Ring:
http://learn.adafruit.com/3d-printed-camera-led-ring

It suggests powering the 5V Trinket with a 3.7V LiPo. Will this work? Surely if it does work then it won't for long!

I've been looking for a 5V LiPo for my 5V Trinket for a while now, have I been wasting my time?!

Thanks in advance.

adafruit
 
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Re: 3.7V LiPo -> 5V Trinket, Camera LED Ring

Post by adafruit »

You can, the 5V trinket can run at lower than 5V, a 3.7V lipo is fine to use although if you want true 5V logic levels, you do need a battery 5V or higher.

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michaelmeissner
 
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Re: 3.7V LiPo -> 5V Trinket, Camera LED Ring

Post by michaelmeissner »

Cool project. I was planning to do something similar with my Olympus E-PM2 and TG-2 cameras, with a 12 or 16 led ring.

I bought a 24 led ring, and I find I cannot power it directly from a lipo battery at 3.7v (the 16/12 led rings that I bought have no problem at 3.7v, but I suspect that perhaps in the future, newer spins of the rings might also require 5v). This means, you can't use a Gemma or 3.3v Trinket without using a voltage booster.

In theory, it may be pushing things to have a 5v trinket with 3.7v input driving a 24 led ring with all white lights at full power (the usual case for a ring light). By my calculation, the ring would try to use 1.4 amps of power. Now perhaps trinkets are better protected, but I did burn out a digispark (same base processor as the trinket) using a similar wiring with a 16 led ring. Hopefully, I am mistaken, and you won't eventually burn out your trinket.

Also note, the recommendations from adafruit of having a resistor between the data pin and the lights, and a filtering capacitor on the power supply. I suspect most people doing rings, probably don't do the best practices. While I currently do not follow the best practices either, I'm planning on redoing my setup, now that I see them in the uber guide.

Adafruit people, it might be useful to offer a PCB/kit that has support for hooking up a battery, with a voltage regulator, resistor, capacitor, etc. for hooking up the rings, lights. My ideal setup would have a mini/micro male USB plug on one side, female type A plug on the other, and a separate battery terminal with a switch connecting either the USB power or a separate battery. The idea would be you plug in your USB power to the board, and from there plug in the microprocessor (the usb data lines would go straight through). The switch would control whether the neopixels get their power from the USB plug or the battery plug. You would then have a voltage regulator, and capacitors. There would be two pins (data and ground) from the microprocessor, and there would be the resistor between the data pin and the neopixel.

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