# Low power, seven segment display

I want to display a 4 digit number on a small device that fits in a hand. I have a CR2032 3V battery at around 230mA, my microprocessor is a 8051 (in a BLE112) usually uses about 0.9µA and I want the device to last as long as possible.

I've looked at the typical seven segment displays, which typically uses a few mA which is too much.

A alternative is the Sharp LS013B7DH01 which is used in Pebble and uses 5 µA, but seems a bit complex for my microprocessor (and expensive)?

There should be some simple low power 7 segment display which has a average power consumption measured in µA (not mA), but I simply can't find it or think of some other solution.

What alternatives do I have?

• How often does the value change? – Ignacio Vazquez-Abrams Oct 11 '13 at 9:20
• When in use, a few times per minute – Hink Oct 11 '13 at 9:37

LCD display without back-light is the only possible solution on these conditions.

Something like this:

Here is some example data sheet: Link to PDF

• Nice, how much energy would it use? – Hink Oct 11 '13 at 9:36
• @Hink - probably several uA. – johnfound Oct 11 '13 at 9:37
• How would I drive it with a 3V (DC) coincell battery in a power efficient way? I found out that I need some separate driver chip which can alternate the current. Preferably I would like to just input numbers via SPI, I2C etc. – Hink Oct 22 '13 at 16:22
• @Hink - but you can generate AC with the outputs of the uC. But IMO, how to do so is a little bit offtopic in this answer. Maybe you have to ask another question about how to control LCD display. – johnfound Oct 22 '13 at 17:12
• Note that you need a minimum of 1 + (7 * 4) = 29 outputs to drive a static 7-segment 4-digit display (no decimal points or colon) as in the linked datasheet. One output drives the backplane (common) plus you need one for each segment. – Spehro Pefhany Oct 23 '14 at 20:49

E-paper displays "stick" at the last value displayed, and only use power to change: http://www.eink.com/

They're a bit of a hassle to drive, and expensive.

Sarkfun used to sell a small E-paper display. https://www.sparkfun.com/products/retired/10150

Perhaps you can locate a different widget vendor for the same.

• – lithiumhead Oct 16 '13 at 7:11