Yesterday I received an order from eBay for a bulk lot of 35 TLC5940's that I bought for $15.00 w/ free 3 day shipping.
I plan on wiring the 32 TLC5940's to an Arduino MEGA to test them.
However when I looked at picture #1 from the Arduino playground, I saw that the TLC5940's use, what appears to be the SPI pins.
In addition, I saw that the datasheet for the TLC5940's has pins 25 & 26 named SCLK & SIN. ((See Picture #2))
Also I know that the SPI pins on both the Arduino Mega are on pins 50 - 53, which would mean that I can not use the same setup as in Picture #1, right?
So my question is how I should wire two pairs of 16 TLC5940's in a daisy chain configuration, and which pins on the Mega I should use for communication.
((Not planning on using the arduino's power to drive the 32 TLC5940. Which will be set to in an adjustable current limiting setup using a Potentiometer))(3mA min // 20mA max)
Also I want to use just one 10k Potentiometer with one 2k resistor in series to control all the TLC5940's IREF pins. Is this possible and will it work? If not is there any way to make it work using just one 2k resistor and one 10k Potentiometer?
TLC5940 Datasheet (In .pdf from www.Sparkfun.com)
Picture #1
breadboard-arduino-tlc5940_close by TECH GEEK ((sgermiller)), on Flickr
Picture #2
TLC5940 by TECH GEEK ((sgermiller)), on Flickr
You daisy-chain the chips according to Figure 12 and Figure 22 of the datasheet.
For maximum speed you would use the SPI pins for connecting to the Arduino. MOSI->SIN, SCK->SCLK, and some pin acting as SS to the XLAT. You would use a different SS for each chain of chips and pull one low at a time. When all the serial data has been sent, raise the SS/XLAT pin to latch the new data.
There is no indication that you can control the maximum drive current from a common signal. I think you have to use separate resistors for each chip. Since the maximum drive current is a characteristic of the LED it should not be hard to pick a fixed value that will work.
Uno 10 = Mega 53
Uno 11 = Mega 51
Uno 12 = Mega 50
Uno 13 = Mega 52
You need to have each chip isolated with its own resistor for the IREF. If you don't then you'll have paths where the chips could feed each other current and completely mess up the reference.
You got a helluva steal on those chips, btw.
Yeah, not a bad price,
compared to $1.60 for similar qty here LED Driver 16-channel 5940 PWM RGB Controller TLC5940 DIP28 TLC5940NT - dipmicro electronics
and $3.08 at Newark. $4.20 at Digikey.
Always wonder if those great deals are counterfeit or something tho.
CrossRoads:
Always wonder if those great deals are counterfeit or something tho.
I got them from a seller who didn't know what they were, she said in the description that her son who moved out left them behind because he didn't need them any more and never used them. The mom also said his interests changed form "building" to "computers". That probably means from hardware to software...
The free 3 day shipping was USPS Ground from 13 miles away.
The reason it was free was because she said "the costs for shipping are included in the price"
Also I tested each one and all work fine. In addition to the fact that they came in same packaging that Texas Instruments sent them in, and only one had even had its pins bent to fit a breadboard.
However, of the total 35 ICs that the original packing slip claimed were included, I only found 32.
That sounds like a great find then! 13 miles, you could have driven over & picked them up.
CrossRoads:
That sounds like a great find then! 13 miles, you could have driven over & picked them up.
Yes your right.
Plus I found the missing 3 ICs that I could not find (they were stuck at bottom)
Also since I now plan on using only a max of 17 total, I am now willing to trade the 18 I am not going to use to anyone who needs some TLC5940 IC's
I will make a new post for any one who may want to trade some stuff that I need for TLC5940(s)
There will be a list for needed items & how many TLC5940(s) you will get for the amount of needed items you trade.