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Author Topic: TLC5940 Overheating (Daisy Chain) ( Electronic Beer Pong Table)  (Read 5031 times)
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So then I need to have 10 Tlc's to support 60 led's running at 20mA's, correct?
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The objective is to manage (juggle) your outputs to achieve the desired result/s: to get your colours and stay within the device limits - that will entail transmitting a lot of data to the device, often. 
[As I see it, you cannot simply write everything to be ON full-bore, as you have been, and move on.]
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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.]

Tie your reference on page 2 of the spec sheet with the figure directly above it on page 1.  The absolute maximum IO of 130mA reference is for each of the outputs (0-15) and NOT all outputs combined.  It wouldn't be much of a lighting and display solution for TI if they could only drive 16 LEDS at 7.5mA each, now would it?
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Anyone want to jump in and verify that each output has a max of 130 mA? (Of course with the right supply power)


Also:

After adding capacitors to the railings, I've been able to run my table for 30 minutes so far without any hiccups. Hopefully this will be a long lasting solution!
« Last Edit: November 04, 2011, 12:00:38 am by saeveritt » Logged

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Anyone want to jump in and verify that each output has a max of 130 mA? (Of course with the right supply power)
Absolute max of 130mA....recommended max of 120mA.

Along with the total power dissipation being below 1572mW calculated using:
PD=(VCC X ICC) + (VOUT X IMAX X (DCn/63) X dPWM X N)
You wouldn't even get close to the thermal max if it were limited to just 130mA total output.
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Anyone want to jump in and verify that each output has a max of 130 mA? (Of course with the right supply power)
Absolute max of 130mA....recommended max of 120mA.

Along with the total power dissipation being below 1572mW calculated using:
PD=(VCC X ICC) + (VOUT X IMAX X (DCn/63) X dPWM X N)
You wouldn't even get close to the thermal max if it were limited to just 130mA total output.


I agree.

Does anyone have knowledge of Photodiodes? I plan on using 1 emitter and 1 receiver under each cup to determine whether the light(controlled by tlc) is active or inactive. Could I wire all of the emitters together and have all of the receivers individually relay information to my mega?

Just purchased 50 of these: http://www.fairchildsemi.com/ds/QS%2FQSD2030F.pdf

(10 extra for backup)
« Last Edit: November 04, 2011, 12:14:14 am by saeveritt » Logged

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Does anyone have knowledge of Photodiodes? I plan on using 1 emitter and 1 receiver under each cup to determine whether the light(controlled by tlc) is active or inactive. Could I wire all of the emitters together and have all of the receivers individually relay information to my mega?

Just purchased 50 of these: http://www.fairchildsemi.com/ds/QS%2FQSD2030F.pdf

(10 extra for backup)

Yes, I played with the idea of having a beam across the top and bottom of the staircase for triggering when someone went onto the stairs.  I quickly dismissed the idea for a couple of reasons.  1.  The emitter needs to be pulsed at 38kHz.  This presented a problem to use with the TLC5940 library since the library uses both interrupts.  2.  They draw a large amount of current (rated at 80mA for the ones you bought) and I wanted it to be more energy efficient when idle.

See this for some sample code and a tutorial: http://www.ladyada.net/learn/sensors/ir.html

Perhaps just a light sensor would work for you?  Not sure what exactly you are trying to detect.....light from an LED or presence of a cup.  If it's light from an LED, I can't think of why you wouldn't know if a LED is on or not since your program turns them on and off.  I'm sure I'm missing something though.
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Does anyone have knowledge of Photodiodes? I plan on using 1 emitter and 1 receiver under each cup to determine whether the light(controlled by tlc) is active or inactive. Could I wire all of the emitters together and have all of the receivers individually relay information to my mega?

Just purchased 50 of these: http://www.fairchildsemi.com/ds/QS%2FQSD2030F.pdf

(10 extra for backup)

Yes, I played with the idea of having a beam across the top and bottom of the staircase for triggering when someone went onto the stairs.  I quickly dismissed the idea for a couple of reasons.  1.  The emitter needs to be pulsed at 38kHz.  This presented a problem to use with the TLC5940 library since the library uses both interrupts.  2.  They draw a large amount of current (rated at 80mA for the ones you bought) and I wanted it to be more energy efficient when idle.

See this for some sample code and a tutorial: http://www.ladyada.net/learn/sensors/ir.html

Perhaps just a light sensor would work for you?  Not sure what exactly you are trying to detect.....light from an LED or presence of a cup.  If it's light from an LED, I can't think of why you wouldn't know if a LED is on or not since your program turns them on and off.  I'm sure I'm missing something though.

Thanks! I'll take a look at the code.

What if you notice on my table, I have 10 circles per side. I am adding a layer of glass on top of the table and need to turn the light's off and on according to if the cup is above the ligh (on a circle) or not.

Here is a terrible drawing.


http://www.youtube.com/watch?feature=player_detailpage&v=vzWEgOt3xsM


Edit: Adding the extra Capacitors did the trick! No flickering, no overheating. I love it! I've been running the fade scope example for 2 hours now and it's still running perfectly. Thanks!
« Last Edit: November 04, 2011, 06:27:02 am by saeveritt » Logged

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Quote
The 130mA Absolute Max is for the device in toto,
Sorry wrong.
Page 3 has recommended operating conditions and it says 120mA for OUT0 to OUT15 when powered by greater than 3.6V.

You need to look at the layout, is it all on solderless board? If so try running a few extra wires power and ground to the chips at the far end. The decoupling should be a 0.1uF ceramic capacitor preferably surface mount but with the leads as short as possible. With hight values like 1uF to 100uF every couple of ICs.

Dang too late!
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  • (Vcc * Icc) + (VOUT X IMAX X (DCn/63) X dPWM X N)   
    (Vcc * Icc) + 2V * 0.12A * ? * 0.9 * 16    (2V * 0.12, Fig.5)
    (Vcc * Icc) + 0.24 * ? * 0.9 * 16             (0.9 assuming high duty)
    (Vcc * Icc) + 0.216 * ? * 16
    (Vcc * Icc) + 3.45 * 1                          (DCn/63) = ? = 1 
    (Vcc * Icc) + 3.45
    Vcc * Icc = ?? + 3.45
So, even w/out (Vcc * Icc) included, 3.45 > 2.45 (dissip. ratings pg.3, at an idealised 25deg_C, and it's worse with heat).

Look, I'm not out to be a d**k, OK, but there's a smoking heap of fried ICs.  For that effect there is a cause, there are no accidents - "Absolute max, Unit" is what they say it is. 
I'm not burning up ICs and some capacitors aren't going to make this go away.

Best of luck.
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  • (Vcc * Icc) + (VOUT X IMAX X (DCn/63) X dPWM X N)   
    (Vcc * Icc) + 2V * 0.12A * ? * 0.9 * 16    (2V * 0.12, Fig.5)
    (Vcc * Icc) + 0.24 * ? * 0.9 * 16             (0.9 assuming high duty)
    (Vcc * Icc) + 0.216 * ? * 16
    (Vcc * Icc) + 3.45 * 1                          (DCn/63) = ? = 1 
    (Vcc * Icc) + 3.45
    Vcc * Icc = ?? + 3.45
So, even w/out (Vcc * Icc) included, 3.45 > 2.45 (dissip. ratings pg.3, at an idealised 25deg_C, and it's worse with heat).

Look, I'm not out to be a d**k, OK, but there's a smoking heap of fried ICs.  For that effect there is a cause, there are no accidents - "Absolute max, Unit" is what they say it is. 
I'm not burning up ICs and some capacitors aren't going to make this go away.

Best of luck.

Do you understand the numbers you plugged in the equation was driving 16 leds with 120mA each?  The discussion was for 20mA each. 

It is understood that all 16 channels cannot be driven at their max.  That is why they include the power dissipation equation.  But at 20mA, the power dissipation is just fine.  Try it.  Let me know what you come up with.  BTW....since dot correction was not stated as being used, DCn=0.  That would make everything past the '+' equal to zero. 
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"It is understood that all 16 channels cannot be driven at their max. "
Untrue.
Someone stated that it's 120mA per output, allowable.  It's not.

The power dissipation is one thing and the max current for the device is another.  1a) Don't exceed the max power dissipation, 1b) don't allow the combined output currents to exceed 120mA.  Anyone can argue till he's blue in the face, or Red-Green-Blue in the face, I don't care.

"BTW....since dot correction was not stated as being used, DCn=0."
No way!  Does nixing pixel correction imply 0, does the datasheet state that?  If that was so, as you noted, then you could do whatever you wanted because everything there gets multiplied by "0/63=0" and everything would then be "0", a free play, and that would make zero sense.

You guys have all the answers, see it your way, have fun: I am not the guy with the burned up ICs.
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"It is understood that all 16 channels cannot be driven at their max. "
Untrue.
Someone stated that it's 120mA per output, allowable.  It's not.



Quote
The 130mA Absolute Max is for the device in toto,
Sorry wrong.
Page 3 has recommended operating conditions and it says 120mA for OUT0 to OUT15 when powered by greater than 3.6V.

You need to look at the layout, is it all on solderless board? If so try running a few extra wires power and ground to the chips at the far end. The decoupling should be a 0.1uF ceramic capacitor preferably surface mount but with the leads as short as possible. With hight values like 1uF to 100uF every couple of ICs.

Dang too late!

Better late then never! I went ahead and added some more 100uf and 1uf capacitors between the IC's.

Do you have any knowledge of using photodiodes to emit using the TLC5490?
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I can read and have read that, the point was that another was implying that that 120mA was per gate X 16.  There's a per sink max, and a total max, and a device power max.  When you exceed any one or a combination then you're in hot water.
As I see it, 20mA X 16 is 320mA and 320mA > 120mA total (Max., Unit)

If everyone else is so right, then why are there these destroyed devices, why is there anything "getting super hot!"?

When are you guys going to solve the problem? 
If you'll just get on with it, I'll be more than happy to sit here and watch.

[Not using dot correction gets you DCn/63=1, not DCn/63=0.]
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As I see it, 20mA X 16 is 320mA and 320mA > 120mA total (Max., Unit)


Maybe it's just a misinterpretation, but I read it as a maximum of 120mA per Channel Drive, not per IC.
I've had the table running for 6 hours now and everything seems to be going smoothly. I've been testing it with the Fade Scope example and the max at any given time for that would seem to be 200mA, which is over the 120mA you are suggesting.




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