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...to connect several 7 segments displays, using as few ports as possible.

I was reading  this guide http://nzlamb.wordpress.com/2010/04/19/multiplexing-7-segment-led-displays-with-arduino/ but looks a bit complicated for my ultra-limited knowledge.

Is there any easier way to get it done?
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Look into shift registers.
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Depending on the seven segment configuration you need the I2C backpacks Adafruit sells might be up your alley. https://www.adafruit.com/products/878
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I'd usually go for the MAX7219. Even my wanky ebay clones seem to work alright smiley
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Depending on the seven segment configuration you need the I2C backpacks Adafruit sells might be up your alley. https://www.adafruit.com/products/878

I guess one of those would really help me but can't find them on local stores, already tried in the past.
Importing is not an option either due government restrictions.  smiley-mad
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I've only marked them down for future purchase, but you might look into TM1638 or TM1640 strips.  Here is a library for the chips: http://code.google.com/p/tm1638-library/

Quoting from the library documentation:
  • The TM1638 module is a module with 8x 7-segment display (8 digits), 8x 2 color (red and green) LED and 8x buttons and is controlled using serial commands.  The TM1638 module is designed to be chainable. It uses only one pin for clock, one pin for data and an additional pin (strobe) for each module you chain up to 6... that's a total of 8 pins for controlling 48 (8x6) 7-segment digits, 48 buttons and 96 LEDs (48 red and 48 green).
  • The TM1640 module is a module with 16x 7-segment display (8 digits) and is controlled using serial commands.

Here is an ebay listing for a TM1638 board with 8 Leds, 8 7 segment digits, and 8 keys from a Chinese ebay vendor: http://www.ebay.com/itm/8-Bit-LED-8-Bit-Digital-Tube-8-Bit-Key-TM1638-module-for-AVR-Arduino-ARM-STM32-/251116139165?pt=LH_DefaultDomain_0&hash=item3a77b0329d
« Last Edit: February 25, 2013, 05:41:42 pm by MichaelMeissner » Logged

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I guess one of those would really help me but can't find them on local stores, already tried in the past.
Importing is not an option either due government restrictions.  smiley-mad

Perhaps it you said where you where someone might know a local source of parts.

Alternatively, it might be good to move to a country with a less restrictive government.
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I've only marked them down for future purchase, but you might look into TM1638 or TM1640 strips.  Here is a library for the chips: http://code.google.com/p/tm1638-library/

Quoting from the library documentation:
  • The TM1638 module is a module with 8x 7-segment display (8 digits), 8x 2 color (red and green) LED and 8x buttons and is controlled using serial commands.  The TM1638 module is designed to be chainable. It uses only one pin for clock, one pin for data and an additional pin (strobe) for each module you chain up to 6... that's a total of 8 pins for controlling 48 (8x6) 7-segment digits, 48 buttons and 96 LEDs (48 red and 48 green).
  • The TM1640 module is a module with 16x 7-segment display (8 digits) and is controlled using serial commands.

Here is an ebay listing for a TM1638 board with 8 Leds, 8 7 segment digits, and 8 keys from a Chinese ebay vendor: http://www.ebay.com/itm/8-Bit-LED-8-Bit-Digital-Tube-8-Bit-Key-TM1638-module-for-AVR-Arduino-ARM-STM32-/251116139165?pt=LH_DefaultDomain_0&hash=item3a77b0329d


But i'm facing the same problem, I don't think I can find those here.


Perhaps it you said where you where someone might know a local source of parts.

Argentina.

Alternatively, it might be good to move to a country with a less restrictive government.

LOL! Not an option for me ATM, but thanks for the advice.
« Last Edit: March 08, 2013, 06:00:14 pm by Rookie2 » Logged

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Can you get individual chips?
TPIC6B595 or 74HC595 with ULN2803 as current buffer, can control both with just 3 pins.
Sink current from common anode 7-segments.
Use PNP to control the common anodes.

Can control common cathode too, need NPNs to sink current, and use shift register to pull current away from the anodes  you don't want on while pullup resistor provides source current.

Or MAX7219 from taydaelectronics to control common cathode.

Maybe from here:
http://www.farnell.com/distributors/agentina_ele.htm
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Yes I think I can get the PICs here, it's just it's the hard way, but it seems I don't have another option right now.
Just let me ask you something..do I need 1 chip for display like in this tutorial? http://www.sqlskills.com/blogs/paulselec/post/arduino-cascading-shift-registers-to-drive-7-segment-displays.aspx
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You could do it with No shift registers, just 7 IO pins to drive the anodes and 4 NPN transistor to sink current from the cathodes.
Or 7 pins to sink the cathodes and 4 PNP transistor to source current to the anodes.
Or 2 shift registers that are daisy chained - one controls the segments, the other controls transistors that sink/source current.
Can you get any shift registers? A part that you can program like a shift register? What kind of availability do you have?
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Can you get any shift registers? A part that you can program like a shift register? What kind of availability do you have?

Yes I can find them here, I will have to check once I have the model I will use, that's what I'm trying to figure right now.
The displays are common anode 7-segments.

Thank you.
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Okay, look for PNP transistors too then if you want to multiplex.
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I've been reading and trying to learn the basics, but it seems to be still too far as for I can get this working by myself.

Would it be too much if I ask for a diagram?
Currently I have the displays (common anode) and I can buy the rest of the components needed.

Thanks in advance.
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Take your pic.

With PNP, can  use shift register to sink the 8 cathodes, TPIC6B595 would be best.
Could use a 2nd TPIC6B595 to sink the current from the PNP gates to turn them on as well, use pullup resistor to pull them high to turn them off.


* 4x7segment_display_4NPN.jpg (62.91 KB, 960x720 - viewed 25 times.)

* 4x7segment_display_PNP.jpg (93.01 KB, 960x720 - viewed 30 times.)
« Last Edit: March 18, 2013, 04:54:20 pm by CrossRoads » Logged

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