0

Trinket and Pixie?
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Trinket and Pixie?

by thinkglobally on Sat Nov 07, 2015 7:27 pm

Can the Trinket play nicely with the 3W Pixie?

My quick review seems to say no - that it only works with an AVR.

Hopefully you can tell me I'm wrong!

thinkglobally
 
Posts: 4
Joined: Tue May 14, 2013 4:21 pm

Re: Trinket and Pixie?

by adafruit_support_mike on Sun Nov 08, 2015 3:23 pm

You can connect a PixyCam to a Trinket, but the Trinket has limited program memory and RAM. You probably won't be able to do anything complicated.

adafruit_support_mike
 
Posts: 52013
Joined: Thu Feb 11, 2010 2:51 pm

Re: Trinket and Pixie?

by Disciple on Sun Nov 08, 2015 9:50 pm

I think the question refers to the high-intensity smart LED https://www.adafruit.com/product/2741, and I'm curious, too. I also wonder how heavy a duty cycle a pixie can sustain without active cooling in free-flowing air of, say, 20 degrees C...and whether any cooling strategies exist for increasing that limit?
(Does this belong in 'glowy things'?)
Thank you.

Hallelujah!
Disciple

Disciple
 
Posts: 554
Joined: Tue Jan 06, 2015 8:13 pm

Re: Trinket and Pixie?

by adafruit_support_mike on Tue Nov 10, 2015 3:17 am

The Trinket doesn't have a hardware Serial port, so you have to use SoftwareSerial, but that should be able to transmit at 115200 baud (which the Pixie LED wants).

WRT temperature, the calculations combine differential equations from thermodynamics and fluid dynamics, and you have to guess at a lot of the constants. In practice, everyone does it empirically and publishes the results as "don't use more than this much power." The datasheet for the LED specs it as having 3W maximum power dissipation, a peak continuous current of 350mA, and a peak pulsed current of 1A for 1ms on no more than a 10% duty cycle:

https://www.adafruit.com/images/product ... RGB-Y2.pdf

You'd get some small advantage from adding a fan, but that's largely irrelevant to LEDs. The unwanted effects of heat happen right at the junction where it's generated, mostly producing lattice defects in the silicon. That increases the resistance through the junction, which generates more heat, which causes more defects, etc. It's an exponential process that starts from a small constant, so it builds up slowly then gets big quickly. The effects are measured as a drop in luminous output, with "time to 50% of initial value" being the figure of merit.

Most LEDs are designed with a half-life between 5000 and 10,000 hours at nominal current, and running at a different current has roughly an x^4 effect on half life. Running at twice the nominal current shortens the half life by a factor of about 16. Running at half the nominal current extends the half life by a factor of about 16.

adafruit_support_mike
 
Posts: 52013
Joined: Thu Feb 11, 2010 2:51 pm

Re: Trinket and Pixie?

by cdunham on Sun Jan 29, 2017 1:02 am

Hi, Mike. Can you quantify what a 10% duty cycle translates to for the Pixie? I'm trying some code like:
Code: Select all | TOGGLE FULL SIZE
void loop()
{
  pixie.setBrightness(100);
  delay(10);
  pixie.setBrightness(0);
  delay(10);
}


but the flickering is very noticeable. Reducing the delay times makes it even more wonky. Some docs talk about a "lower brightness with periodic pulses". What does that mean, exactly?

cdunham
 
Posts: 9
Joined: Sat Feb 28, 2015 5:43 pm

Re: Trinket and Pixie?

by franklin97355 on Sun Jan 29, 2017 12:42 pm

For the loop above a set value of 50 would be equivalent.

franklin97355
 
Posts: 18556
Joined: Mon Apr 21, 2008 2:33 pm
Location: Lacomb, OR.

Re: Trinket and Pixie?

by cdunham on Sun Jan 29, 2017 1:06 pm

franklin97355 wrote:For the loop above a set value of 50 would be equivalent.


Ah, that makes sense. I was thinking of this incorrectly. In looking through his code, it looks like the "duty cycle" he is referring to is internal PWM settings based on the "brightness" setting, not me flipping the thing on and off :-/

Thanks!

cdunham
 
Posts: 9
Joined: Sat Feb 28, 2015 5:43 pm

Re: Trinket and Pixie?

by jfishstik on Thu Apr 19, 2018 6:52 pm

This is my first project. My mom let me order a Trinket 3.3V and a Pixie because it wasn't expensive and I wanted something simple to start with to see if I can make them work together and make different colors and brightnesses of light. Will this work? I know how to solder and connect things but I am looking for a place to start experimenting. I can download code and know how to make changes to it if I understand the right tool I need. Text editor, or something more complicated? I guess I need the most basic tutorial..

jfishstik
 
Posts: 1
Joined: Thu Apr 19, 2018 6:41 pm

Please be positive and constructive with your questions and comments.