Driving three large 7.5v common anode 7-segment displays with Arduino

7segmentdisplayarduino

I'd like to drive three common anode 7.5v 10ma 7-segment displays using my arduino uno and a few 74HC595N shift registers. The problem is the uno only outputs 5v 40ma on the digital pins.

I am considering inverting the 5v-out to -5v using an ICL7660. The -5v could then be placed at the anodes for a 10v total drop.

I have a few questions before trying this out-

Would the ICL7660 sink enough current to drive all three 7-segments? Are there other drawbacks? Is there a better solution?

Resources:
The 7-Segment Display
ICL7660 Arduino tutorial

Best Answer

No, the 7660 is of no use. It can only supply enough current for a couple of segments, let alone displays.

The easiest (not necessarily the cheapest) way to get enough voltage for this display is to use a DC-DC converter, such as a TDK CC3-0512SF-E:

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This one will output 12V at up to 250mA, so for a 3-digit display 10mA/segment is okay.

You will also need one resistor per segment of about 470 ohms, three ULN2003A darlington arrays.

If you have 9-12V available somewhere else, you won't need the DC-DC converter, but you will still need the resistors and the ULN2003As.

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