LED Matrix
rapscaLLion
Posts: 75
Hey all,
I need to control around 500 individual LED pixels. They will be 20mA, White, On/Off only.
I have ideas, but it seems cumbersome. Anyone have any experience with a project like this?
Thanks!
I need to control around 500 individual LED pixels. They will be 20mA, White, On/Off only.
I have ideas, but it seems cumbersome. Anyone have any experience with a project like this?
Thanks!
Comments
You could look at the Sparkfun RGB matrix schematic to see how they did it...
I noticed that some people use these chips: TLC5940
I guess you have to decide if you want to do common anode or common cathode.
I'm using some PMOS fets and darlington arrays as well as a demultiplexer...
If you're brave, you could also look for Clemen's post on "Charliplexing"
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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
My Prop Products:· http://www.rayslogic.com/Propeller/Products/Products.htm
Oooh! That sounds fun! Do you have pics yet?
Lots of hobbyists have done this before with different chips and such...
The thing I hope to do differently is be able to drive each LED and near it's rated average current...
Should allow it to work in full sunlight...
Just today I was thinking it would be neat to add in an accelerometer, but then noticed that someone already
did a project like that... It's hard to come up with something unique!
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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
My Prop Products:· http://www.rayslogic.com/Propeller/Products/Products.htm
the TI application note focus.ti.com/lit/an/slva346/slva346.pdf talks about how to use one of their chips for high current applications.
Anywho, while researching I've seen several recommendations to actually drive the leds at currents higher than their ratings to help overcome the percieved decrease in brightness resulting from the sequenced nature of the driving scheme.· Apparently, it is safe to do this because the led's can dissapate the heat during their 'off' time.
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Leon
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Amateur radio callsign: G1HSM
This thread seems useful:
http://forums.parallax.com/showthread.php?p=667572
Some good comments from the lesser-spotted DeSilva.
Graham
The total current gets to be quite large with 8x8xRGB all on at full brightness. At 20 mA DC each, that comes to 3840 mA or about
20 W of 5 V supply power.
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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
My Prop Products:· http://www.rayslogic.com/Propeller/Products/Products.htm
I've made a 4x4x4 RGB led cube, propeller powered.
It drives 192 leds in PWM mode, and for the drivers I use the ALLEGRO A6818 chips, each one can drive 32 leds.
I use one chip for each color, driving the anodes, and one ULN2803 to drive the cathodes.
The leds are arranged as an matrix.
If you are interested, I can give you the whole code, i've develloped a 192 bits PWM routine wich can certainly be ehanced.
Attached are some pictures of my cube
Best regards from FRANCE
Very cool display
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Life is fun with a Prop.
BillS
··· Louisville KY.
I'm thinking that the Prop is well suited to driving an 8x8xRGB array without external driver chips.
Even with 32 outputs, you'd need a few to drive the matrix and they seem to be ~$4 each.
I think I can do this directly from the Prop, hopefully just as well, and maybe even better...
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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
My Prop Products:· http://www.rayslogic.com/Propeller/Products/Products.htm
And you can get 24bit full color without any special PWM driver (using only a programming tip).
I did it recently, but I never wrote about it in the forum, I got a full color led screen using simple on-off drivers with more than 30fps video.
I think it could be possible too, controlling leds directly from pchip too.
It is a challenge Ray, you can do it too, I'm sure.
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Regards.
Alberto.