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Author Topic: 14 segment with register shift  (Read 835 times)
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I have 13 of 14 segment displays on board. I assume we need to add register shift to use 14 segment display. Can someone tell me what kind of register shift should we use and how many register shift do we need for 13 of 14 segment displays? Do we need to add transistor and resistors on it? What kind of transistors and the value on resistors to I need for it? Is there schematic for it?

Reid
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I have 13 of 14 segment displays on board. I assume we need to add register shift to use 14 segment display. Can someone tell me what kind of register shift should we use and how many register shift do we need for 13 of 14 segment displays? Do we need to add transistor and resistors on it? What kind of transistors and the value on resistors to I need for it? Is there schematic for it?

Reid

Knowing nothing about the segment displays or how they're connected I can only offer general advice.

If you multiplex the displays then you can set them up as common-anode or common-cathode. Then you connect your 14 segments to individual outputs on a 16 bit shift register. For your 13 digits, you either need a driver or you can use a transistor to switch each one on. You'll have to work out resistor/transistor values based on your specific hardware.
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For 14 LEDs you need two shift registers.

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Is there schematic for it?
I think there is an example in the shiftOut() reference on the Arduino site.

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Do we need to add transistor and resistors on it?
If you use the popular 74xx595 shift reg you will need transistors (+ base resistors + current-limiting resistors) to drive the LEDs.

A better way is to buffer the SR with a driver chip like the ULN2803 (?) but you still need current-limiting resistors.

The best way is to use a constant-current driver chip like the TLC5916 or TLC5927, these are shift regs with all the driving circuitry in them. Or use one of the many MAX multiplexed driver chips.

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Rob

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Rob Gray aka the GRAYnomad www.robgray.com

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