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Topic: Problem with multiple tlc5940 (Read 9521 times) previous topic - next topic

Grumpy_Mike


Like this?

No between the +5V line and ground. This looks like you have it across the LEDs. Also you should be using large electrolytics here, like 47uF not 0.1uF ceramics.

quizz_kid

Fungus, that´s not the fade demo running, it´s the code from the first post in this thread, but with a few more LEDs added.

Grumpy, sorry I´m such a noob, I´m not sure where the 5v lines are located. Maye you can point them out using this pic

Grumpy_Mike

The 5V line is the common line to all the LEDs. The ground line is the ground on the TLC chip.

fungus


Fungus, that´s not the fade demo running, it´s the code from the first post in this thread, but with a few more LEDs added.



It looks an awful lot like the fades demo to me (or at least, a version that somebody hacked without knowing what they were doing).

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

quizz_kid

Ok, I bought some 47uF´s... Put them between 5v and gnd, but I guess I´ve put them wrong(picture below), because that didn´t change anything.



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Help please

Grumpy_Mike

They are in the right place but you seem to have taken off the 0.1uF ceramic caps you had on earlier, why?
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

Dcoupling might not fix a wiring problem, but it still is needed. The layout is a bit messy but then I never did like solderless bread boards anyway.

Try as a temporary measure reducing the TLCs drive current to see if you have a power supply issue.

quizz_kid

I added the 0.1uFs, and still no change. Hmm...

How do I reduce the drive current on the tlc?

Hippynerd

Im not sure by your picture, but I think you may have the 47 cap on it wrong. I think you want positive lead on the chip, and the negative lead on the ground of of chip, or the ground rail.

by reducing the load, I think what he means is change the resistor that sets the current level for the LEDs. I think its 2k in the demo for 20ma, If you change that to 4k, it I think that will set if for about 10ma.
https://sites.google.com/site/rgbledcubes

Grumpy_Mike

Quote
Bigger Bigger Smaller Smaller Reset Reset Reply with quoteQuote
Im not sure by your picture, but I think you may have the 47 cap on it wrong. I think you want positive lead on the chip, and the negative lead on the ground of of chip, or the ground rail.

No you have the cap on pin 22 which is where it should be.

Quote
think its 2k in the demo for 20ma, If you change that to 4k, it I think that will set if for about 10ma.

Yes that is right.

quizz_kid

I cant seem to find a 4k resistor anywhere... Does it have to be 4Kohm?

Grumpy_Mike

It is the resistor on pin 20 of the chip.
What value do you have?
Double it.

quizz_kid

ok... put two 2k in series then  = 4k. Still no change though. Other suggestions?

quizz_kid

In case I can´t fix this issue with the TLC5940's, is there another way to get 30 LEDs to breathe smoothly in different duration/speed?

Hippynerd


In case I can´t fix this issue with the TLC5940's, is there another way to get 30 LEDs to breathe smoothly in different duration/speed?


Nearest that i can tell, about a million ways. seriously there are a lot of ways to control leds.
https://sites.google.com/site/rgbledcubes

Grumpy_Mike

So time for some fault finding.
Use the code that just lights up one device, I think you said that still worked, chech it still does.
Then switch over the input to the other chip by changing the input wire only. If that now works it is your software that is wrong. If not then it is wired wrong.

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