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Author Topic: TLC5940 Overheating (Daisy Chain) ( Electronic Beer Pong Table)  (Read 4767 times)
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Texas
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Ok, well currently I am at (5 x .06) + (5 x .02 x 16) = 1.9, which is under the limit of power dissipation.
My setup is:


I just pulled out the 10k pull-up resistor. Mainly because I was getting fed up with all of my fried chips. (4 of them!)

It seems to only be the first one taking the damage, it is getting super hot! Does anyone have any suggestions?

12v into Mega's Vin, 5v and 2A for the RGB led's common annode, 5v from arduino to power tlc's

Here is what I have so far:


I'm currently running on a Mega

Mega pin 51 (MOSI) -> SIN (Tlc pin 26)
Mega pin 52 (SCK) -> SCLK (Tlc pin 25)
Mega pin 11 (OC1A) -> XLAT (Tlc pin 24)
Mega pin 12 (OC1B) -> BLANK (Tlc pin 23)
Mega pin 9 (OC2B) -> GSCLK (Tlc pin 18)


LED Datasheet: https://docs.google.com/open?id=1vwge5JS-4A-AJEv53ObcY4Knkq1JKmPyuO3D0Z3LMx2U6tL-tSeY2NN-7sdY
« Last Edit: November 03, 2011, 01:09:49 am by saeveritt » Logged

Dubuque, Iowa, USA
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Where is the "5V and 2A" for the LEDs supplied from?
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Nice start for your project.  I see where your priorities are though.   smiley-lol

When I was working on my RGB LED Stairs Illumination project with 6 TLC5940s to drive 30RGB LEDs, I initially had some overheating issues as well (fried two TLC5940s) but was able to overcome them after doing a tear down of my breadboard and setting it back up along with adding some additional jumpers across the power rails.  I'm powering mine with a L7805CV (5v 1.5A) regulator with heatsinks added and a 7.5V 3A wall wart.  When I started with a 12V wall wart, the VR would overheat.  My power with the illumination routines I run peaks at about 1.4A which is too close to the max for my comfort and the VR is only barely getting warm but I'm still going to change it.  I have an external 5V 3A power supply that I've tested on my bread board setup running all 30 RGB LEDs at full brightness (~1.8A) for an hour and it worked wonderfully.  The TLC5940s barely got warm while each was supplying 300mA to the LEDs.

1.9A is too close to the 2A capability of supply power.  Your arduino needs power as well as the TLC5940s to run.  You may be dropping voltage down too much with a struggling VR.  Is it getting hot?  If so, do you have heat sinks on it?  Have you measured the measured the max current of the entire circuit?  Are the fans drawing power from the 5V 2A power as well?  What is the rating of the 12V source you mentioned?
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Texas
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Thanks for the quick replies!


1.9A is too close to the 2A capability of supply power.  Your arduino needs power as well as the TLC5940s to run.  You may be dropping voltage down too much with a struggling VR.  Is it getting hot?  If so, do you have heat sinks on it?  Have you measured the measured the max current of the entire circuit?  Are the fans drawing power from the 5V 2A power as well?  What is the rating of the 12V source you mentioned?

5v 2A is powering just the 20 RGB led's across the anodes. (60 Led's running at 20mA each)

My arduino is powered by 12v into the Vin. The rating of the 12v source is  5A and 60W. (Also powering my fans)
the second 5v power supply is from the arduino's 5v. This is for the Tlc5940's.

Where is the "5V and 2A" for the LEDs supplied from?

From a wall wart, it's completely separated from the other power supply.
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5v 2A is powering just the 20 RGB led's across the anodes. (60 Led's running at 20mA each)

My arduino is powered by 12v into the Vin. The rating of the 12v source is  5A and 60W. (Also powering my fans)
the second 5v power supply is from the arduino's 5v. This is for the Tlc5940's.

Now I have a better picture of what you were trying to explain.  smiley

From the looks of things, I can see nothing wrong with the schematic.  When I fried the two TLC5940s, it was also the first in line now that I'm thinking about it.  I think mine was a loose/bad connection.  Any flickering of the LEDs?
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Texas
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Now I have a better picture of what you were trying to explain.  smiley

From the looks of things, I can see nothing wrong with the schematic.  When I fried the two TLC5940s, it was also the first in line now that I'm thinking about it.  I think mine was a loose/bad connection.  Any flickering of the LEDs?

Yes! The flickering is mainly coming from the 3rd and 4th Tlc's. I've tried switching to 3.3v for the chips, but that causes even more flickering!

I tried it out today, low and behold another chip has fried!
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The expression is Lo and Behold!.

http://en.wiktionary.org/wiki/lo_and_behold
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Yes! The flickering is mainly coming from the 3rd and 4th Tlc's. I've tried switching to 3.3v for the chips, but that causes even more flickering!

I tried it out today, low and behold another chip has fried!

I would guess either bad connection or voltage issues.  I had voltage issues on some of the rails.  Try running additional jumpers to power the rails, moving where the power is coming into the bread board to a different rail or adding additional/larger capacitors on the rails.  This helped a lot with my issue.  And once I went to my circuit board, everything was solid.
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You can't have all 16 outputs on, 20mA each; the Absolute Max output current for the unit is 130mA (PDF, pg. 2)
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You can't have all 16 outputs on, 20mA each; the Absolute Max output current for the unit is 130mA (PDF, pg. 2)

I've been reading this as the Max for a single OutX!


I would guess either bad connection or voltage issues.  I had voltage issues on some of the rails.  Try running additional jumpers to power the rails, moving where the power is coming into the bread board to a different rail or adding additional/larger capacitors on the rails.  This helped a lot with my issue.  And once I went to my circuit board, everything was solid.

Doing that as we speak, what size capacitors would you recommend?

The expression is Lo and Behold!.

http://en.wiktionary.org/wiki/lo_and_behold


Well, I learn something new everyday. Thank you!
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You can't have all 16 outputs on, 20mA each; the Absolute Max output current for the unit is 130mA (PDF, pg. 2)

I've been reading this as the Max for a single OutX!


I would guess either bad connection or voltage issues.  I had voltage issues on some of the rails.  Try running additional jumpers to power the rails, moving where the power is coming into the bread board to a different rail or adding additional/larger capacitors on the rails.  This helped a lot with my issue.  And once I went to my circuit board, everything was solid.

Doing that as we speak, what size capacitors would you recommend?

I agree....that current limit is the absolute max for a single sink.  I'm about to use some TLC5940s to drive some 3w LEDs and plan on tying 8 outputs together to sink 350mA per IC.
PD=(VCC X ICC) + (VOUT X IMAX X (DCn/63) X dPWM X N)

PD= (5 * 0.03) + (3.8 * .044 * 8 ) = 1.49W <-- within power dissipation limits of the IC.

As far as capacitors, I really don't know if there is a great way to select the right one or not.  Perhaps someone more knowledgeable in these things can pipe in.  I used a couple of 1000uF and a couple of 100nF.  The 100nF was a given and the 1000uF was experimentation.
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You can't have all 16 outputs on, 20mA each; the Absolute Max output current for the unit is 130mA (PDF, pg. 2)

I've been reading this as the Max for a single OutX!


I would guess either bad connection or voltage issues.  I had voltage issues on some of the rails.  Try running additional jumpers to power the rails, moving where the power is coming into the bread board to a different rail or adding additional/larger capacitors on the rails.  This helped a lot with my issue.  And once I went to my circuit board, everything was solid.

Doing that as we speak, what size capacitors would you recommend?

I agree....that current limit is the absolute max for a single sink.  I'm about to use some TLC5940s to drive some 3w LEDs and plan on tying 8 outputs together to sink 350mA per IC.
PD=(VCC X ICC) + (VOUT X IMAX X (DCn/63) X dPWM X N)

PD= (5 * 0.03) + (3.8 * .044 * 8 ) = 1.49W <-- within power dissipation limits of the IC.

As far as capacitors, I really don't know if there is a great way to select the right one or not.  Perhaps someone more knowledgeable in these things can pipe in.  I used a couple of 1000uF and a couple of 100nF.  The 100nF was a given and the 1000uF was experimentation.

Could you maybe make a crude paint drawing of how you jumped from the rails and added capacitors? Any particular areas?
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Could you maybe make a crude paint drawing of how you jumped from the rails and added capacitors? Any particular areas?

Here's a pic of my bread board setup.....I haven't torn it down yet.  It looks a mess but it works great! smiley

Click for a larger image.  Does this help?
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Texas
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Here's a pic of my bread board setup.....I haven't torn it down yet.  It looks a mess but it works great! smiley

Click for a larger image.  Does this help?



I love running into helpful people like yourself! Thank you! I'm going over everything right now, I'll let you know how it goes.
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The 130mA Absolute Max is for the device in toto, just like the other items called out on page 2 there, it's not "per sink". 
The sum (total) of your outputs, at any time, ought to be less than that absolute max figure, if you go beyond that then stuff starts frying.

[I'm helpful, I'm telling it like it is.]
« Last Edit: November 03, 2011, 10:12:34 pm by runaway_pancake » Logged

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