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Topic: PCA9685 & LED control  (Read 1 time) previous topic - next topic

kylefoster

Hi guys,

I've been building a project using WS2812B strips. It's effectively a 10x35 led matrix, using 10 strips and it's all working fine including the coding. Robert (crossroads) is doing a great job of developing a PCB design for me but I've hit a hurdle for my prototype which will in all likeliness affect his design.

The problem I've run into is that this matrix is going behind a red tail light lens and I need some of the strips to show amber through the red lens. This is working to an extent using the green LED within the WS2812B modules but it's just not bright enough.

The lens seems to be 'muting' a lot of the brightness of the green. So although it's showing orange, it's very dim. The next thing for me to test is to get brighter LEDs and I only need these strips to be green so a single colour would be fine.

So my theory is to chain a few of the PCA9685 boards together:

https://www.adafruit.com/products/815

To control a high number of individual high brightness green leds. Is this a good idea? Is there a better or simpler way of doing it? These boards also have PWM functionality but I'm not sure if I need this since I only need to be able to turn each LED on and off etc. I was thinking of using these LEDs:

https://www.adafruit.com/products/300

These have a 'brightness' of 8000mcd and from what I can find, the WS2812B green varies but is roughly 1000mcd? I've also seen other 'super bright' LEDs that claim upto 12000mcd. I've ordered some so I'll see for myself but can anyone confirm how bright they really are?

I need the LED's to be 'addressable' since I'm trying to achieve a cyclone effect and the only way I know how to achieve this is to add more pins to the Arduino.

Any help would be greatly appreciated and I'm so grateful to everyone's help so far with both my code and my prototype.

Kyle

CrossRoads

Can you turn on more of the Green color in that area, so more LEDs are on?
Or maybe use WS2811 instead of WS2812B so that external LEDs  like high brightness parts can be used.
Have to check on SMD availability.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

kylefoster

Hey Robert!

Thanks for the quick reply as usual!

I've tried 100% of the green brightness and turning on the entire matrix to do tests, if that's what you mean. I think the LEDs themselves need to be much brighter.

Audis latest lights have completely red lenses and also amber turn signals so I'm not sure how they do it.

So how do the WS2811 chips work? Do you only need 1 per x amount of LEDs or 1 per LED? Also, how many data pins are needed etc?

Bear in mind that this post was only to aid in my prototype to make sure it's working so would the WS2811 chip help for that? Is it available as a breakout etc.

Thanks again,

Kyle

kylefoster

I've done a bit of reading up on the ws2811 chip and what you suggested makes total sense Robert.

So it seems you can control 3 single colour leds per chip and you can chain them so only 1 pin is needed 'per strip' as before. So it would be affectively like making your own addressable strip?

Thanks again,

Kyle


CrossRoads

Quote
So it would be affectively like making your own addressable strip?
Exactly. Only the LED to be used is user selectable.

Can probably find LED strips made that way too if  interested
https://www.google.com/#q=ws2811+led+strip
Have to read carefully, not all that show up are WS2811 based.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

kylefoster

Thanks Robert,

'only the led to be used is user selectable'?

I've tried googling these strips to help with my prototype but they all seem to be rbg or white and I think, considering how bright these will need to be, I'm better off using dedicated bright single leds.

Strange that addressable strips like this don't seem to exist.

Kyle

CrossRoads

Quote
'only the led to be used is user selectable'?
Yes, you the user get to select the LED that is wired to the controller.
The LED is then turned on under Arduino control via the WS2811.
You could use 3 Green LEDs if you wanted, or two Green and one Red if those are the colors you are after
(with the Green looking like Amber thru the Red lens?)
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

CrossRoads

Not so strange they don't exist, the integrated controller/LED devices (Neopixel with I2C type timing and more recently the Dotstar with faster SPI type interface (clock & data)) have just replaced them.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

INTP

Quite daft to try to overpower a lens filter with simply more light of a blocked wavelength.
Depending on your local regulations, maybe you'll be okay without amber. Just red for all functions other than white for reverse.
Else I'd start looking into aftermarket taillight housings that are more amenable to your plans.

kylefoster

Thankfully, the reverse lights are total separate so all I have to worry about are the brakes/running lights and turn signals.

The turn signals definitely have to be amber over here in the UK so I need to experiment a bit more. As far as I know, no other lens for this specific application exists (apart from clear but it would defeat the purpose of my project in my opinion).

I've asked this very question on the Adafruit forum also and it's been pointed out that although the RBG led (when using the green and red together) looks yellow, there are of course 2 seperate colours. The green is muted as I mentioned so only the red is getting through.

I think I need to play around with some single colour leds, yellow, amber and also green just to see how the brightness of my chosen led will affect the outcome?

Thanks again,

Kyle

CrossRoads

Quote
I think I need to play around with some single colour leds, yellow, amber and also green just to see how the brightness of my chosen led will affect the outcome?
You've got the lens, so I guess so.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

INTP

Sure you can play around. But that's all you'll be doing, playing around to see for yourself that you've wasted money and can't achieve what you want simply with a brighter wrong color.

Can you remind us what year/make/model of car this is and what the taillights look like or what your goal is? I'm curious how the turn signals currently work and if you're planning on not using them or what.

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