Small ~60mA Serial Controlled LED Driver Recommendations  - Page 1
Forum section: electronics / projects

author: Twistx77
author_rank: Regular Contributor
timestamp: March 15, 2014, 03:40:05 pm
content: Hi,I'm trying to find a driver for 4 group of leds that are apart from each other 40mm and 40 mm apart from the connector that provides them with power and control. I've attached a simple diagram of what I want to do.In the diagram I've made the L are the LEDs, the S are light sensors and C is the connector that supplies power and control for every LED and get the sensors signal.Each LED can be powered with up to 60mA of current and I need to control the power of each independently with at least 8 different power values. They have to be switched on with the correct power value and switched off again in less than 1ms so the driver have to be fast enough to do that. The driver should be controlled with a one-wire or serial interface if possible to reduce the number of lines I have to use in the connector.First I tried with a board that I already had with an ULN2803A to test it. It worked but since the cable was about 600mm long the relative high current switching in the cable produced spikes in the sensors output that could go up to 4.5V when they were supply with 3.3V. So to avoid that I want to have one driver under each LED or each group of LEDs. In the worst case I would have an 8 channel driver similiar to a TLC5940 close to the connector to drive all the LEDs and then use separate the LED's and Sensors supplies.I've been looking for a suitable driver but I can't find any. I really like the WS2811 used in LED strips but they are DIP package and hard to find in suppliers like Farnell. I've also seen the TLC59731 but it have a problem and is that they can only supply 50mA and I would like them to have at least 80mA to be able to drive the LEDs at 60mA or even 70mA.Anyone know an alternative to the WS2811 or anything that could be suitable for me? I even thought of using a digital pot that could handle the power because it would not need the pwm switching for the LED but I'm not sure if exist any digital pot for that kind of power or that kind of speed. Anyway I would accept any ideasThanks!

author: I_may_be_drunk_right_now
author_rank: Contributor
timestamp: March 15, 2014, 04:31:15 pm
content: Is this for a light curtain or in any way safety related?

author: Twistx77
author_rank: Regular Contributor
timestamp: March 15, 2014, 04:37:48 pm
content: No, not for a light curtain but it have to be safe

author: David_AVD
author_rank: Super Contributor
timestamp: March 15, 2014, 10:28:18 pm
content: You can buy WS2811 chips in SOIC8 package from Ray Wu on AliExpress.

author: Twistx77
author_rank: Regular Contributor
timestamp: March 16, 2014, 10:19:11 am
content: Hi,SOIC8 is a bit too big and even if it wasn't AliExpruess for me is not a good distributor, tomorrow I might not find the same product anymore.Thnaks!

author: dannyf
author_rank: Super Contributor
timestamp: March 16, 2014, 11:45:21 am
content: QuoteThat's true, to a lesser degree maybe, with any supplier.

author: Twistx77
author_rank: Regular Contributor
timestamp: March 16, 2014, 12:31:43 pm
content: Yes, you are right but at least using TI or AD or any other mayor company its harder for that to happenand also using Farnell I can have them at home the next day. Good luck getting the Ali Express stuff in less than a week.Well, I can't seem to find the solution that I want so what do you people think of using a driver like the TLC5940 to drive the LED from one of the edges of the board? Do you think I could overcome the noise well using separate supplies?