Pages: [1] 2 3 ... 5   Go Down
Author Topic: 6x TLC5940 32 rgb leds  (Read 10182 times)
0 Members and 1 Guest are viewing this topic.
Denver, CO
Offline Offline
Jr. Member
**
Karma: 0
Posts: 54
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset


I have a working setup of 32 rgb leds, two chips per color. I was wondering if it would be easier to somehow rewrite the library to have 3 S-inputs (one for each color). Or would I have to connect them all together in series and have 0 -31 for red 32 -63 for green and channels 64-92 for blue.

I want to expand it to  192rgb leds but that will require 36 chips but it looks like the code is limited to 16 chips. Is there anyway to expand this?

Thanks in advance!
Logged

Massachusetts, USA
Offline Offline
Tesla Member
***
Karma: 212
Posts: 8967
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Which "the code" are you talking about?

How often do you need to update each LED?
Logged

Send Bitcoin tips to: 1L3CTDoTgrXNA5WyF77uWqt4gUdye9mezN
Send Litecoin tips to : LVtpaq6JgJAZwvnVq3ftVeHafWkcpmuR1e

Manchester (England England)
Offline Offline
Brattain Member
*****
Karma: 637
Posts: 34581
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
I want to expand it to  192rgb leds but that will require 36 chips
The problem here is that cascading so many chips you run into fan out problems, that is the number of inputs any one output can drive. This means you will have to have buffers driving the common lines split up into groups of 10 or so.
One way to get round this is to use multiplexing but the LEDs are dimmer unless they can take more current. This is my project for using 64 RGB LEDs using only three TLC5940s.
http://www.thebox.myzen.co.uk/Hardware/Hexome.html
Logged

Denver, CO
Offline Offline
Jr. Member
**
Karma: 0
Posts: 54
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

http://youtu.be/3a3ulbgmOKo

Is my setup and I I have a rainbow pattern working but after a few minutes it starts flickering as shown here.

http://youtu.be/84lL1j7yphE

I know I should make a function to simplify the code but I"m not that advanced yet.

Thanks Grumpy Mike thats a great idea to control many leds with fewer chips but the information would have to be the same. I guess it would be a trade off.



Logged

Denver, CO
Offline Offline
Jr. Member
**
Karma: 0
Posts: 54
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

I slept on it and I think the erratic behavior is because I need a higher current voltage regulator.
Logged

Manchester (England England)
Offline Offline
Brattain Member
*****
Karma: 637
Posts: 34581
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
but the information would have to be the same.
I don't understand this, the information on the LEDs can be anything you like. The trade off is that they are dimmer because they are multiplexed but you can compensate by using more current through the LED.

Quote
I think the erratic behavior is because I need a higher current voltage regulator.
It could be, are they getting hot? Have you got enough decoupling capacitors on the chips, it was hard to see on the video. I would also add a 100uF across the supply as well, close to one of the chips.
Logged

Denver, CO
Offline Offline
Jr. Member
**
Karma: 0
Posts: 54
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

The chips themselves were cool to touch but the heatsink on the lm7805 was hot as heck. With the rainbow code it is turning on at least 64 leds on at a time @ 20ma each it pulls more than the 1amp 5v can handle so I have ordered a bunch of LT1083 that can handle the higher amperage.

I will need to build a bunch of power supplies or I was thinking on building 1 power supply with many 5v rails. > Is there such a ~12vac transformer rated at 50amps or something like that?

As for the multiplexing of chips I'm not sure if I fully understand. For simplicity say for bank 1 of leds you want all red so you send the code and enable the anode of bank 1. If you wanted bank 2 of leds all red as well you would just enable the anode line for it and it all works well (maybe a little dimmer). Now lets say you want bank 1 all red and bank 2 all green at the same time. How can they be addressed differently if they are all tied to the same 5940 chips (at the same time)?
Logged

Manchester (England England)
Offline Offline
Brattain Member
*****
Karma: 637
Posts: 34581
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
the lm7805 was hot as heck. ........ so I have ordered a bunch of LT1083 that can handle the higher amperage.
It will do you no good, the heat it generates will be exactly the same. The only way to make it cooler is to lower the input voltage or put it on a heat sink. See:-
http://www.thebox.myzen.co.uk/Tutorial/Power.html
and
http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.html

Quote
Is there such a ~12vac transformer rated at 50amps or something like that?
Yes but there is no way you are up to building a power supply of that size. I would find it a challange.

Quote
As for the multiplexing of chips I'm not sure if I fully understand.
You enable a bank and send the data for that bank. Then do it for the next and the next and so on. The code does this and knows nothing about what LEDs are on or off, it just ships the data to the chips. Your working code then only has to bother with setting or clearing bits in the data. So the same chip is outputting different data for each bank that is enabled.


Logged

Denver, CO
Offline Offline
Jr. Member
**
Karma: 0
Posts: 54
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

So now I want to use higher power leds for my project such as a 3w rgb led:
http://www.superbrightleds.com/moreinfo/component-leds/vollong-3w-rgb-high-power-led/899/

This shows how to do it and I figured I'd use a bunch of 2n2222 transistors. It shows the output of the tlc4940 to the emitter and I would have to calculate the base resistor tied to vcc. 
http://www.ti.com/lit/an/slva280/slva280.pdf  (#3 alternate solution)

I ordered a 40amp 5v power supply which should suffice. Should I assume Beta is 100 for a 2n2222 transistor? If so it looks like I should have a 1ohm resistor for the base for a 400ma red and 1.1ohm for 350ma green/blue. Is that right? Is that ideal or should I bump up the Vcc to 12v or higher? Also in the diagram the show the anode connected to VLED(VGB) will that be the same as Vcc?

I'm now using this project to power side emitting fiber optic and the 3w led works noticeably better. I bought that one 3w led but i'm open for suggestions if there are better ones out there.


Logged

Manchester (England England)
Offline Offline
Brattain Member
*****
Karma: 637
Posts: 34581
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

All sorts of wrong with that.
1) You can't run a 3W LED with just a series resistor, you need a constant current source.
2) A 2n2222 can't handle the current.
3) That data sheet doesn't show you how to drive high power LEDs.
4) If you have decoupling problems with a low power LED these get multiplied with high power LEDs.
Logged

Denver, CO
Offline Offline
Jr. Member
**
Karma: 0
Posts: 54
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

I happy to say after getting a more powerful power supply the problems I had went away.
Logged

Denver, CO
Offline Offline
Jr. Member
**
Karma: 0
Posts: 54
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

So I have followed This post > http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1271193991 for each output and it works great except I have both V1 and V2 tied together as they are both 5V and I do not need an indicator led1.

I keep frying the tlc5940 chips. I have noticed it happens when I unplug/plug it in otherwise when it works it keeps working for a long time. I'm thinking I getting a surge in current somewhere. Should I have a separate 5v supply for just the chips or should I put an inductor/cap on the +5v supply?

I have a 40amp 5v power supply
Logged

Manchester (England England)
Offline Offline
Brattain Member
*****
Karma: 637
Posts: 34581
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
these peaks are coming out of the shaping amplifier
I hope you are not plugging in a chip with the power on, that will kill most things.
When they go does it get hot?
Is there more than one supply? You should not let an unpowerd chip be connected to a powerd input / output line.
Logged

Denver, CO
Offline Offline
Jr. Member
**
Karma: 0
Posts: 54
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Yeah I noted the order of what I plugged things in and when they fried this morning after I posted. Yeah it gets freaking hot, good thing they are only a few bucks.
Yeah it has a separate 12v supply for the arduino with the grounds connected. I think the finished product will have one plug powering the arduino and have the arduino turn on a relay for the 5v supply to avoid this problem. Awesome thanks for clarifying!

Here is what I have so far > http://www.youtube.com/watch?feature=endscreen&NR=1&v=NjePJYSYDgM and http://www.youtube.com/watch?NR=1&feature=endscreen&v=Yc1n5oc-0ME

3 more board to prototype out and I'll be half way done.
Logged

Manchester (England England)
Offline Offline
Brattain Member
*****
Karma: 637
Posts: 34581
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Nice videos, it looks to be comming along well.
If the TLC chip is getting hot I should look at the power calculations in the data sheet. it looks a bit daunting at firse but it breaks down into simple parts. You should not be dissapating much here so try and minimise the current. It is probbly the heat that is killing the device more than the power switching.
Logged

Pages: [1] 2 3 ... 5   Go Up
Jump to: