I thought of you guys when I came across this 16 Channel LED Driver (TLC5940). I've never used it but I may be interested in using it in the future and with the LED and POV signs, I believe there may be some future usefulness here.

http://focus.ti.com/lit/ds/symlink/tlc5940.pdf

Very nice indeed. Since all of my projects revolve around LED's

Heres some nice 16 channel led drivers..

http://uk.farnell.com/catalyst-semicond ... dp/1656115

these are very good and controlled using only 4 serial connections, they can also be linked together, as i have used them before, the only problem is, is that they only come in SMD style, which are a little tricky to solder, I brought some SMD adaptors and brought some pins from ebay, so you can use the SMD style drivers on a breadboard, check out the website below for an example of the adaptors.

http://www.futurlec.com/SMD_Adapters.shtml

Thats quite a good price for those drivers as well.

I am guessing that they use some kind of constant current source so that the LED's have a nice uniform brightness?

The problem that I have with using transistors is that the more led's that are turned on the dimmer they get.

Yeah i thought they was a good price too Brad

When i used them, i used a BC637 transitors to supply the current (5volt)to the leds, as the current output on those transitors seemed high enough to give you a good led brightness, so yeah this gives you your current souce, but this can be controlled on and off with your microchip aswel if you connect your transistors to your microchip..

I dont know if you notice on the datasheet on these SMD you can change a resistor on the RSET pin which also controls your led brightness?
i think i used 1k8 resistor and connected 16 Leds.

http://www.farnell.com/datasheets/83808.pdf


heres a picture of the setup

I am guessing that you are using a separate resistor for each LED?

by the way, I like your profile image

Cheers for that Brad, I thought my profile image was just the thing for your site hehe!

and no i didnt use a resistor on each LED, thats an advantage of using a constant current sink driver, is that almost any LED can be used and the supply current remains constant regardless of the LED forward voltage. If the output current does need to be altered, it only requires the current setting resistor on the RSET Pin of the led driver CAT4016W-T1 to be changed, so being only one resistor is needed

Heres a picture of some CAT4016W-T1 on a adaptor i made up with pins, so I could use them for breadboard experiments.. as these chips only come in SMD format..

Of course! I didn't think of that

The constant current source adjusts its own resistance to make sure that the current flowing is constant - therefor the LED's will just grab their forward voltage drop - leaving the rest for the current source.

You have made me rethink my LED designs...

Cool stuff! I hope ive helped you rethink your led designs in a good way Brad, I think your led designs are really amazing, Ive built your 8x8 game system and learnt from your projects from your old site, I hope I can return some of my knowledge

I will certainly look at buying some of those LED drivers.

Glad you like the projects. It would be great if I had more time to make more