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Pixie heat management in lightsaber
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Pixie heat management in lightsaber

by Ace_Player on Sat Aug 17, 2019 10:33 am

Hi all,
I know this topic has been addressed a few times, but maybe someone has found a good solution since then.

I'm building a lightsaber per the Adafruit guide, but I'm experimenting with different LEDs. Brightness is my main problem, since I'm using the heavy grade plastic blades from ultra sabers. Right now I'm trying to figure out how to mount the Pixie to a LED heat-sink, or dissapate heat in some way. I'm only using a single Pixie, and it will hardly ever be set to 255,255,255. Since it's a lightsaber, the LED may be turned on for several minutes at a time.
I'm driving all this with the Feather m0 express and Featherwing prop-maker. The lightsaber hilt is made of aluminum.

Please let me know if anyone has any ideas.
Thanks!

Robert

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Re: Pixie heat management in lightsaber

by XRAD on Sat Aug 17, 2019 10:38 am

AdaMike's replay at:
viewtopic.php?f=8&t=118278

the issue with the pixie is the board/ electronics on the backside preclude a direct conducting heatsink mount. Unlike the 'cree' type lightsaber LEDs which are mounted on the aluminum heatsink, but do not have the electronic capabilities built in.....
Last edited by XRAD on Sat Aug 17, 2019 10:45 am, edited 2 times in total.

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Re: Pixie heat management in lightsaber

by Ace_Player on Sat Aug 17, 2019 10:41 am

Addendum

I have also tried the following lighting solutions, each with its own results:

3-9W star shaped LED - Can't get it bright enough with the Feather m0 express. The LED api doesn't seem to have a brightness setting. (or I missed it!)

Neopixel jewel - This would work wonderfully, but it just barely doesn't fit in the LED holder. I'd have to file it down about 1mm.

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Re: Pixie heat management in lightsaber

by XRAD on Sat Aug 17, 2019 10:50 am

I have used the ada pixies in several projects and they are easy to code for and very bright. You could try the pixie in a mock-up build, and if turns off too much from overheating, consider other options....

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Re: Pixie heat management in lightsaber

by adafruit_support_bill on Sat Aug 17, 2019 10:58 am

3-9W star shaped LED - Can't get it bright enough with the Feather m0 express.

You can't drive high wattage LEDs like these directly from a microprocessor. You need a driver that can handle the high current requirements. Something like one of the dimmable "Buck Puck" drivers. OR you can DIY with a MOSFET as in this project: https://learn.adafruit.com/bedazzler/overview

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Re: Pixie heat management in lightsaber

by Ace_Player on Sat Aug 17, 2019 11:26 am

Following off of that link, would this guide get me started? I am familiar with the basics, but have not dealt with MOSFETs before, so I am a bit apprehensive.

https://learn.adafruit.com/rgb-led-strips/usage

So it looks like I'll need 3 MOSFETs for a single 3W RGB LED such as this:
https://www.adafruit.com/product/2530

What about for it's bigger cousin?
https://www.adafruit.com/product/2524


Thanks!

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Re: Pixie heat management in lightsaber

by adafruit_support_bill on Sat Aug 17, 2019 12:26 pm

The MOSFETs in the store can handle the 3/9W LEDs easily.

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Re: Pixie heat management in lightsaber

by Ace_Player on Sat Aug 17, 2019 12:43 pm

Thanks!

Do I need a MOSFET for each color channel, or is there a 3 in one?

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Re: Pixie heat management in lightsaber

by adafruit_support_bill on Sat Aug 17, 2019 1:31 pm

If you want to control the color, then you would need 3 MOSFETs.

A possible 'all-in-one' solution would be the ULN2803A: https://www.adafruit.com/product/970
There are a couple catches though:
1) Each channel is rated for 500mA. So you would need to double-up and use 2 per color to get full brightness. But with 8 channels, you have enough for that.
2) There is about a 1v drop through the darlington transistors. So you would have trouble driving the blue channel if you are powering from a 3.7v LiPo. A 3xAA alkaline pack (4.5v) or would work.

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