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Topic: Problem arduino Duemilanove and TLC5940 (Read 3503 times) previous topic - next topic

geppou

Nov 16, 2013, 06:37 pm Last Edit: Nov 16, 2013, 11:24 pm by geppou Reason: 1
Hello,
I searched in latest topic for a solution for my problem but I didn't found it.
I'm using an only one TLC5940 an Arduino Duemilanove and 16 green leds connected from pin0 to pin15 of TLC and it NOT WORK correctly!
I connect all the others pin correctly from TLC to Arduino (I control many times from guide from Internet and from the datasheet of TLC)
and I'm Using the famous library on this link https://code.google.com/p/tlc5940arduino/ , I put the decupling capacitors on supply(but I'm sure that is not the problem because the only thing that change is the brightness of the leds)...
The code I'm using is simply the BasicUse Example from the Library but the problem is always the same : the code works sometimes and when it work some leds (8-9 leds from 6 to 13-14 always the same and sometimes others leds ) blinking randomly with HIgh flash...WHY?
Can anyone help me please?

fungus

Advanced Arduino

geppou

I use the pin configuration that you post with pin7 substitute with pin11 because the picture is wrong....and all datas in fact are send correct to the leds  but sometimes and some leds blinking independently from the code and I don't understand why

fungus

Try adding a small ceramic capacitor (eg. 0.1uF) between +5V to GND on your TLC5940. Put it as close to the +5V pin as you can.
Advanced Arduino

geppou

#4
Nov 17, 2013, 11:49 am Last Edit: Nov 17, 2013, 12:10 pm by geppou Reason: 1
i try to put 2 capacitors in parallel because I don't have 0.1 uF capacitor(the 2 capacitors have 47 nF everyone so 94 nF in parallel ) conected on pin 21 and 22 but the TLC don't work and it's a bit overheated....then I try to change TLC but it's the same thing...help please

fungus

It's probably some sort of wiring problem, but I can't see your breadboard from here.

Check your GND connections carefully, make sure there's connection to GND on the Arduino. Don't trust wires/breadboards, measure resistance from the GND pin on the TLC to the USB connector case on the Arduino.

Similarly the +5V - measure from the TLC pin to a separate wire in one of the Arduino 5V connections.
Advanced Arduino

geppou

i Try to measure the resistance between GND of TLC and usb case of arduino and it is similar than the resistance between the TLC 5V and arduino 5V however now all leds are on all the time and I don't know why instead before all led was off all the time....I try to change the TLC with another and even the ATMega chip but is always the same problem....the first time worked sometimes now it's all wrong

fungus


i Try to measure the resistance between GND of TLC and usb case of arduino and it is similar than the resistance between the TLC 5V and arduino 5V


Is it zero?
Advanced Arduino

geppou


fungus

OK,  there's the problem!

Both 5V and GND pins should have zero resistance between Arduino and TLC.

Advanced Arduino

geppou

#10
Nov 17, 2013, 04:27 pm Last Edit: Nov 17, 2013, 04:29 pm by geppou Reason: 1
but how can i solve this problem?
Initially I thought that using an external supply could solve the problem but is the same...In fact when I use power supply from arduino or from an external supply I see that to the voltage between the GND and 5V  of the TLC is little less than 5 volt(~4.85 Volt)...this problem is connected with the reason that the resistance between the GND and 5V is not Zero?

fungus

#11
Nov 17, 2013, 05:20 pm Last Edit: Nov 17, 2013, 05:22 pm by fungus Reason: 1

but how can i solve this problem?


I don't know, I can't see what you're doing.

There should be a zero Ohm from the TLC GND pin to the Arduino GND. Find out why there isn't.
Advanced Arduino

geppou



I don't know, I can't see what you're doing.

There should be a zero Ohm from the TLC GND pin to the Arduino GND. Find out why there isn't.



Today I do some tests and I see that also using an external 5V supply to TLC and arduino connected to the USB(so the 5V of arduino is floating but obviously the GND of arduino is connect with the GND of TLC and the GND of external supply) when the external supply is OFF, between the 5V and GND of the TLC the tester sign 0.36 V why? the only supply is from the USB of arduino but it isn't connect with the circuit(is connect only the GND) and when I turn ON the external supply between 5V and GND of TLC there is 4.78 V and not 5V(happen the same if I connect the arduino supply only,without the external supply)

if you want fungus I can take a photo of the circuit but it is a bit complex to understand the connections

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