Go Down

Topic: LED Driver TLC5940 / Library Compatible to TLC5940PWPR ? (Read 351 times) previous topic - next topic

Amazonasmann

Hello,

As a beginner I have a question regarding the electronic piece TLC5940. While looking for my first arduino project, I found a guide I am looking forward to do. The guide uses 2x TLC5940 (which I figured out is actually a  TLC5940NT). There is a library for TLC5940 which is also mentioned here: https://playground.arduino.cc/Learning/TLC5940/. However this TLC5940NT seems to be rather expensive on the usual websites like amazon etc...because it seems to be obsolete. On several electronics website I always find the TLC5940PWPR or TLC5940QRHBREP first which costs like 2€ a piece.

I am not too confident about my electronics knowledge but I assume they are suited for the task (connecting 25 LEDs and control them individually).

Now they all seem to share the same datasheet but I am wondering if the library I want to use also works for this piece of electronics?

What is the actual difference between those? The TLC5940NT being obsolete, will the existing library for TLC5940 still work?

TLC5940NT

TLC5940PWPR

Grumpy_Mike

#1
Aug 13, 2019, 05:15 pm Last Edit: Aug 13, 2019, 05:25 pm by Grumpy_Mike
The links don't take you to anything but the first page.

Generally speaking in electronics the letters tagged on the end of a part number refers to things like the package type and temperature specifications and such. The chip itself will work the same and so the library will.

Search for those extra letters in the data sheet.

It is a bit of an old chip and you would be better off using a WA2812b strip of LEDs these days. They are much simpler to drive.

The information you need is in the PACKAGING INFORMATION section starting at page Addendum-Page 1 at the end of the data sheet, Note that a HTSSOP package is a surface mount part and is tricky to solder if you are a beginner.

ReverseEMF

However this TLC5940NT seems to be rather expensive on the usual websites like amazon etc...because it seems to be obsolete. On several electronics website I always find the TLC5940PWPR or TLC5940QRHBREP first which costs like 2€ a piece.
As is often the case, in this Hobbyist Unfriendly world of electronics, the "NT" version of this IC is the "Through Hole" or "DIP" package.  And the DIP version was obsoleted, since the DIP package is not used in "the industry" so much anymore--since manufacturers prefer what is called "SMD" or "Surface Mount". 

Here's what a DIP [or PDIP] "through hole" package looks like:



And here's a HTSSOP [also known as simply the SSOP] surface mount package:

Note: There is a subtle difference between the two, above, packages, that might not be readily apparent.  The DIP package has pins that point down, whereas the SSOP package as pins that point out.

And here's a quite different kind of surface mount package [there are hundreds!] called a VQFN:



BTW: There is "Package" [also called "Case"], and then there is "Packaging", which is an entirely different thing.  The Package [or Case] is what the "chip" [the piece of silicon that provides the functionality] is housed in.  The packaging is how all the little packages are delivered -- which can be in a tube, or in something called "tape", etc.  It's kind of like the difference between eggs in a carton [the carton being the "package"], and the grocery bag [the packaging], which is used to carry one or more egg cartons to your car.  Or, even better: The yoke is like the chip, and the egg shell is like the Package, and the egg carton is like the Packaging.

And, this discussion is not complete without mentioning the intricacy of all those letters [and sometimes numbers] that follow the actual part number.  Every manufacturer has their own system.  The TLC line of ICs are offered by Texas Instruments, and, basically, in this case:

"NT" stands for their "PDIP" package.
"PWP" is their "HTSSOP" package.
"RHB" is their "VQFN" package.

And then, that can be followed by an "R" or a "T" which seems to have something to do with the number of ICs in a "Package" -- but there seems to be any discernible logic there!?!

Go figure!


...but I assume they are suited for the task (connecting 25 LEDs and control them individually).
Well, you would need two of these ICs [two TLC5940's] to individually control 25 LEDs -- unless by "LED" you mean an RGB "LED", which is, actually, 3 LEDs in one!  In the later case, you would need 5 of these ICs.  And, Grumpy_Mike has a point: Using something like a string of [what I think he meant] WS8212B "LED"s [another case of something commonly called an "LED" that is not just an LED, but is a combination of three LEDs -- one Red, one Green, and one Blue -- plus some micro-circuitry to convert serial commands into light intensities for each of the three LEDs].

BTW: There is also a library for driving WS8212Bs -- Adafruit offers one for the Arduino that they created for their "NeoPixel" LED strings -- and it works for any WS8212B based string [not just the NeoPixel line].  Check it out at: https://learn.adafruit.com/adafruit-neopixel-uberguide

What is the actual difference between those? The TLC5940NT being obsolete, will the existing library for TLC5940 still work?
Yup.  But, you will have to deal with Surface Mount parts.  Not impossible, but a bit more difficult.  One possibility is the Schmartboard -- which makes hand soldering surface mount chips a lot easier.
"It's a big galaxy, Mr. Scott"

Please DON'T PM me regarding what should be part of the Public Conversation -- Let it ALL hang out!!
Unless, of course, it's to notify me of a mistake.

Amazonasmann

Thanks for your advice and good explanation!
Regarding LED stripes (for example WS8212B): Let's say I would like to do a square, it will not be possible unless I cut it in pieces. How would I reconnect those individual pieces? Solder? jumper wires?

Grumpy_Mike

#4
Aug 13, 2019, 10:16 pm Last Edit: Aug 13, 2019, 10:33 pm by Grumpy_Mike
Quote
How would I reconnect those individual pieces?
Yes wire and solder is good.
However you can get several matrix displays based on these chips, ready built. Just google
ws2812 matrix
and you will see lots of examples.
This is one I have used:-
https://www.ebay.co.uk/itm/8x8-64-LED-Matrix-WS2812-LED-5050-RGB-Full-Color-Driver-Board-For-Arduino-F-T5H3/283114378205

This is a picture of a matrix I made using a slightly different sort of LED strip that has 4 connections and not 3 but the idea is the same.


The solid wires just go horizontally at the back of the board.

ReverseEMF

Regarding LED stripes (for example WS8212B): Let's say I would like to do a square, it will not be possible unless I cut it in pieces. How would I reconnect those individual pieces? Solder? jumper wires?
Typically these strips are designed to be cut [they even, usually, have a little "scissors" icon that shows where to cut].  This will leave a set of copper pads on each side of the cut.  And, yes, the best way is to solder wires to these pads.  Just reconnect it as it was before the cut.

And make sure to read the Adafruit NeoPixel Überguide -- especially the "Best Practices" section. 
"It's a big galaxy, Mr. Scott"

Please DON'T PM me regarding what should be part of the Public Conversation -- Let it ALL hang out!!
Unless, of course, it's to notify me of a mistake.

Go Up