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Topic: Big 7 segment modules (Read 3286 times) previous topic - next topic

bld

I ordered a bunch of 2.3" 7 segment modules, but I have never tried to play around with any of those before, not even small ones.

I looked at this page, and found that maybe this is the one to use for them http://www.arduino.cc/playground/Main/MAX72XXHardware but anyone more into this that can give me some advise on this while I am waiting for them to arrive.

My plan is to only use 4 of them at first, or maybe 6, to make a big wall clock.
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Grumpy_Mike

That link said your display had:-
Forward Voltage: 7.5V

MAX72XX data sheet says
Maximum voltage 6V.

It is not going to work.

bld

Maybe a 4511B would be better then,  if I read the data sheet right, it should be able to handle more voltage, and also the needed current.
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Grumpy_Mike

It depends on what sort of 4511B is it a CD4511B or a 74HC4511B or a 74LS4511B

You might have to voltage convert the signals from the arduino up to the Vcc of the device if you run it at a higher voltage.

bld

Looks like it would need a lot of pins to use that too...

What about a MAX72XX with a ULN2003A on? so the ULN2003A would drive the display instead?
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Grumpy_Mike

Yes it could work but I haven't played around enough with the chip to draw you a schematic. You would have to invert the signals as the ULN2003A will pull down when fed with a high.

bld


Yes it could work but I haven't played around enough with the chip to draw you a schematic. You would have to invert the signals as the ULN2003A will pull down when fed with a high.

Ah yeah... hmm, I wonder if there is an opposite ULN2003A that will do it without changing anything. Or an entire other thing to use instead.

But by searching MAX72XX, it looks like it is the easiest by far to do what I want to do.
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runaway_pancake

#7
Nov 02, 2011, 03:45 am Last Edit: Nov 02, 2011, 03:56 am by runaway_pancake Reason: 1
As those are C.A. displays... the 7-segment data could be shifted out into 74hc595s (daisy-chained), each '595 output to a ULN2803 input, each segment cathode connected to a '2803 output.

added pic
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

CrossRoads

Also check this Application note

APPLICATION NOTE 1196
Using the MAX7219/7221 to Drive Higher Voltage or Current
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Chagrin

A TLC5916 is a DIP-package shift register that will provide eight current-sinking outputs, perfect for each digit, and $1.65 qty 1 at Mouser. Each digit would be tied onto a bus with 3 or 4 data lines, 5V, GND, and one additional positive voltage line to drive your LEDs (up to 20V). You only need one decoupling cap and one resistor (to set the current) to complete the circuit for each digit.

Attached is the code you would use to drive four digits. I stripped it down a bit from what I was using for a similar project so it's a little funky with how it handles the digit string to be displayed.


bld


A TLC5916 is a DIP-package shift register that will provide eight current-sinking outputs, perfect for each digit, and $1.65 qty 1 at Mouser. Each digit would be tied onto a bus with 3 or 4 data lines, 5V, GND, and one additional positive voltage line to drive your LEDs (up to 20V). You only need one decoupling cap and one resistor (to set the current) to complete the circuit for each digit.

Attached is the code you would use to drive four digits. I stripped it down a bit from what I was using for a similar project so it's a little funky with how it handles the digit string to be displayed.

Also a good idea, I wonder if I also could put a MOSFET on it, so I could use pwm to control brightness, would be handy to have it a bit less bright when the room is dark. Or make it do something fancy.
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Chagrin



A TLC5916 is a DIP-package shift register that will provide eight current-sinking outputs, perfect for each digit, and $1.65 qty 1 at Mouser. Each digit would be tied onto a bus with 3 or 4 data lines, 5V, GND, and one additional positive voltage line to drive your LEDs (up to 20V). You only need one decoupling cap and one resistor (to set the current) to complete the circuit for each digit.

Attached is the code you would use to drive four digits. I stripped it down a bit from what I was using for a similar project so it's a little funky with how it handles the digit string to be displayed.

Also a good idea, I wonder if I also could put a MOSFET on it, so I could use pwm to control brightness, would be handy to have it a bit less bright when the room is dark. Or make it do something fancy.

If you read the datasheet you'll find there's a way to adjust the output level of the chip from the maximum set by the resistor.

bld

Yes, I can set it with a resistor, but I was thinking more about making it fade up and down, controlled by the arduino.
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