I did some quick searching and multiplexing with the TLC5940 is possible. so you could do with 3 TLC's. However 10 TLC's would be easier I guess but more expensive. When you have 10 TLC's you don't have to multiplex, every led has got its own driver. You could use the library I posted before. I've just tested it with multiple TLC's and it works fine. Every leds gets it's own position in the array. When you multiplex every driver is shared with 8 other leds. This means that 7/8th or the time a led is turned off.With the TLC5940 you can set the PW(M) and/or the DC. So you've got two methods to adjust the brightness. I don't know how the PWM of the TLC will work with the PWM you generate when multiplexing. maybe you could just leave the TLC's PWM on 100% and only adjust the DC. I've never actually used multiplexing so I'm only a novice there.As far I can tell from the photo he's only able to set a led on or off and not dim. If you need a simple latch register check out the 74HC595, cheap and the code is on Arduino Playground.
Immediately I discovered that I could NOT use Sparkfun's RGB led with the 5940. Short explanation: The Sparkfun component has one lead as the Cathode (negative) connection, and the three other leads are Anodes (positive) for each of the colors. The 5940 chip is a "cathode sink" design (I think I'm saying that right) which means that the ports for the LEDs on the chip deliver negative polarity. To uniquely control each color I would need a "common anode" LED, or three separate R G and B leds. Argh.
The 5940 chip is a "cathode sink" design (I think I'm saying that right) which means that the ports for the LEDs on the chip deliver negative polarity.
QuoteThe 5940 chip is a "cathode sink" design (I think I'm saying that right) which means that the ports for the LEDs on the chip deliver negative polarity. If you mean it has 1 lead as the anode and 3 separate cathodes, the term is "common anode"."Cathode sink" doesn't really mean anything.
Google "cascading tlc5940" and "cascade tlc5940"Eberhard
I had a suggestion of a guy to drive the 64 RGB leds:using only one MAX7221 + 3 transistorand cycle one channel color at a time with transistor.someone could help me to draw/design that on the paper???see u
QuoteI had a suggestion of a guy to drive the 64 RGB leds:using only one MAX7221 + 3 transistorand cycle one channel color at a time with transistor.someone could help me to draw/design that on the paper???see uany ideas ??
the more advanced option is 3 max7221 chips each driving each color channel, however since there is a common cathode for all 3 chips that you have to cycle through the chips anyways, turning them off so there led sinks go high (this is only on the 7221, the 7219 you can't do this) so i dont think it would really be more benefit than the single max + transistors.
Julienb,you might look at 3 chips that I have found. One is the allegro A6280 3-Channel Constant-Current LED Driver with Programmable PWM Control http://www.allegromicro.com/en/Products/Part_Numbers/6280/index.aspThe other is Silicon Touch Technology DM413 http://www.siti.com.tw/product/spec/LED/DM413.pdf also their DM412. http://www.e-neon.ru/user_img/catalog_datasheets/dm412-a.003.pdfI am doing a project that uses the DM412 and have found it relatively easy to interface. Each RGB LED is driven by a DM412. You shift out 48bits for every LED you have in your line and either toggle the strobe line or send a special software strobe by holding the clock high and sending 8 pulses on the data line.I see that Digikey and Newark sell the Allegro chip but only in the qfn package. Sparkfun soldering tutorials have encouraged me that surface mount is possible but I have yet to tackle that.The DM412 I am using is in a commercial LED product that I am hacking. The company engineers told me that is what is in it. I'm not sure they want me broadcasting this info. Besides they charge $10 a node for their waterproof string of LED's.I first tried the BlinkM but it was not bright enough for my outdoor application and the i2c bus is prone to noise problems over the 100 feet I want to string the lights. A cool thing about all these chips is that they cascade the data and clock from chip to chip keeping the logic levels clean and perky.
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