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Topic: Connect my led strips (12v) to arduino  (Read 7387 times) previous topic - next topic

KeketteStyle

Hello guys ! @ReverseEMF, you're giving too much information than I can't understand :D. I repeat, I am a beginner.

Good news, my scoreboard project is growing :


I have build first 2 digits but I noticied something.. More leds segments are ON and less leds shine. How can I give same voltage/Intensity to each led segment ?

This is my circuit :


I am using 1 ULN2803 per digit and I connected together 2 shift registers. Someone can explain me how to make brighter my leds ?

thanks you guys. I wish you good holidays ! :)



Paul__B

You need to check your 12 V supply voltage for the different combinations of LEDs.

Check the common ground connection to Arduino, 74HC595s, ULN2803s and the 12 V supply.

I'm not on holidays any time soon.

DrDiettrich

I have build first 2 digits but I noticied something.. More leds segments are ON and less leds shine. How can I give same voltage/Intensity to each led segment ?
Sounds like you have too few resistors in your design. Each LED, or series of LEDs, needs its own current limiting resistor.

KeketteStyle

Ok Paul I will check I Come back :)

I have 0 resistors :o that s mean is bad ?? It can explain performance of my leds?

DrDiettrich

#34
Aug 04, 2018, 06:58 pm Last Edit: Aug 04, 2018, 06:59 pm by DrDiettrich
What's the current of a LED row, and the power of your 12V supply?

Wawa

OP is using LED strips, with resistors on the strip.
So no extra resistors needed.
Leo..

Paul__B

#36
Aug 05, 2018, 01:08 am Last Edit: Aug 05, 2018, 01:09 am by Paul__B Reason: That too.
What's the current of a LED row, and the power of your 12V supply?
See first post.

And answer #7.

KeketteStyle

6 LEDs per row.
Someone have a good Idea ? :)

DrDiettrich

I still think that the supply voltage is important. Check the voltage when only few segments are lit, and when more are lit. Fractions of a volt may make a difference, i.e. a switching transistor already may cause problems. I'd try to increase the supply voltage to 14V or 15V, if the strips support that.

ReverseEMF

#39
Aug 05, 2018, 05:41 pm Last Edit: Aug 05, 2018, 05:51 pm by ReverseEMF
If I read you correctly, you're saying that in some cases, when more than one LED strip is powered, all of the LEDs in those strips, dim down, as if the addition of one or more strips is loading something down...is that right?

And, assuming I got that right, here are a few possibilities:

  • Upon close examination of the photo you supplied [https://zupimages.net/up/18/31/klvm.jpg], I see what appears to be fat, foil ribbons running to the various LED strips.  In a few cases it looks like a couple of LED strips are "daisy-chained" together,  In other words, a foil ribbon goes to one LED strip, then from the other end of that LED strip extends another foil ribbon until it reaches yet another LED strip.

    If that's the case, and if these are power lines, then what could be happening is, the daisy chained path may be presenting a high enough series resistance as to inject a significant voltage drop, thus dimming the LEDs.  Because of the fairly sharp LED Forward Voltage curve [i.e. exponential relationship between forward voltage and current], it doesn't take much of a voltage drop to cause a significant dimming.  

    You really should run separate power lines to each LED strip, all running back to a common point, as near to the power source as possible [or if that's not practical, then you need a hefty "power buss" that those lines can run to].  A power buss is merely a conductor with sufficient bulk to minimize voltage loss at the highest in-circuit current levels [which is, usually, a combination {or adding} of all the simultaneous currents that will flow through the buss].
  • Another possibility is the overloading of the power source.  If ALL of the LEDs are dimming at once, then that points to the Power Source as the problem [or it could be a high resistance point in a common power line--see #3].  If the power source voltage is dipping because too much current is being drawn [or because the power source is failing], then that will cause the LEDs to dim.  Once again, it doesn't take much of a voltage dip to dim an LED.
  • Similar to #2, if there is a common power line, or common connection point from the power source, this might be the source of the dimming.  A way to test for this is to get a small[ish] gauge wire [i.e. a fat wire] and, when you see the dimming [of the LED(s)], jumper across all potential problem sources--i.e. provide a temporary "good connection".  If the LEDs brighten up, you're closing in on the culprit.  Process of elimination will guide you to the weak link.  If any of the LED current is traveling down any of the buss lines on that protoboard, then THAT very likely could be the source of the dimming.
  • The ULN2803s have internal current "clamp" to the tune of 500mA on each output, and an overall limit of 2.5A.  If more current than these limits is occurring, that would cause a dimming.  So, a current inventory might be in order.
  • Another possible source of dimming could be in your code [I don't see a listing anywhere].  If there is any sort of multiplexing or PWM involved, and if the pattern of this changes, such that the duty-cycle is different when the dimming occurs, then that's your problem.  This could occur if, say, a code loop executes faster when only one LED strip is lit, but runs slower when two, or more, are lit.  Something like that.  This is unlikely, but I mentioned it for completeness ;)
"It's a big galaxy, Mr. Scott"

Please DON'T Private Message to me, what should be part of the Public Conversation -- especially if it's to correct a mistake, or contradict a statement!  Let it ALL hang out!!

KeketteStyle

Thnaks a lot Reverse :) My power supply was dying.. I changed it and now it works perfectly !
I'll send some pictures when I finish my board.
See you :)

KeketteStyle

Hola, I have some problems :(

I was running my scoreboard, after 1 hours, my arduino mega fried.. (saw sparks on ship in middle board). My arduino mega was very hot ! Why it fried ?
On my scoreboard I have :
- power supply 12v 2A (to connect my Leds)
- 7x2 segments (=2 digits). Each digit = 6 Leds. Each segment runs on 12v
- Each digit are connected to ULN2803 then to shift register
- I have resistors only on my segment leds



Maybe I should use 9v ? Arduino uno is better than arduino mega ? I forgot some resistors ? Tell me please :)

See you guys !

ReverseEMF

Based on your limited "schematic" [more like a block diagram], things seem to be arranged correctly, so:

  • Something happened related to something obscured by lack of information.
  • Something just, plain-and-simple, failed on the Mega (it should be able to handle 12V just fine, and it doesn't look like [again, based on sketchy information] anything is drawing excessive current from the Mega)
  • Maybe water splashed on the Mega -- that would do it -- especially salt water!
"It's a big galaxy, Mr. Scott"

Please DON'T Private Message to me, what should be part of the Public Conversation -- especially if it's to correct a mistake, or contradict a statement!  Let it ALL hang out!!

DrDiettrich

Sparks on ship or strip?

Replace the sparkling item and continue.

KeketteStyle

Sparks on my arduino mega :(
here :

No water, It was running close of me then I saw that.

It works well for 1 hour and then... boom

Maybe I should reduce voltage ? (my arduino is burning, that's normal ?)


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