Hi,
I am working on an idea for a connected children's toy.
I currently have a prototype with two tlc9540 chips that cuts out after a few seconds. Before I work out the problem, I just wanted to confirm it was the best component for the application... I have started having some doubts.
My requirements are:
What LED drive would you recommend?
There's nothing wrong with the TLC5950 for this.
Depends on the LED. Be more specific.
I am using 5mm RGB LEDs... my circuit that isn't working has two TLC9540 with 10 RGB LEDS (common anode, linked below). Will the chips be okay to light all 10 RGB LEDs at once?
http://proto-pic.co.uk/5mm-rgb-led-common-anode/
My circuit at the moment funs a a single LED on/off sequence for 10 seconds and then simply cuts out.
Here is my circuit, is there anything obviously wrong? http://25.media.tumblr.com/ec3be9a6a01334bbfb18df174f7876d8/tumblr_ml50ra9Hsb1so48cuo1_1280.png
30 LEDs (10 RGB LEDs) at high current (20mA each) will draw 600mA. That can overpower the onboard regulator if you are using the barrel jack for power, or if using the USB for power (500mA limit).
For testing, knock the current down a lot.
Also check your connections - another poster was having problems with two TLC5940 as well, turned out to be miswiring on 1 pin. Subtle, but enough to cause erratic behavior.
Thanks CrossRoads.
What is the max current of the TLC9540 limited to (I can drop a few LEDs)? Would current still be the issue as I have only run a sequence of one LED on and one LED off... never more than three on at once.
I still haven't got it working, I am still trying to find the issue.
TLC5940 can do a lot of current.
Many folks use them with 16 LEDs.
tlc5940.pdf (1.06 MB)
Your schematic shows you are powering it with 3.3V. If you are pulling that from an Uno's 3.3V then you're limited to the 50ma the Uno can supply.
Try switching everything to 5V which has a ~1A limit. There should be no need to change your Iref resistor or anything else.
Thanks, I tried switching to 5V from the UNO and get nothing... 5 of the RGB Leds are dimly lit.
When I plug it into 3.3v, I am not only getting the RED LED illuminating in the programmed sequence.
These have a power dissipation of 60mW where as Red and Green can dissipate 130mW... does that give anything away?
I had this working on a breadboard... now the PCB has failed, I have checked all the connections and it seems the same as the breadboard (on the PCB I am using the RHB version where as on the breadboard I have the NT chips, so I may have made a mistake in translating the format).
I am gonna go back to the breadboard and get it working again.
Another thing I just noticed... when it cuts out, the only way to get it going again is by taking the ground to the TLC5940 in and out. If I reset the arduino or take the power cable out again it doesn't reset this.
