07 June 2016

A clock with Arduino and four HP 5082-7300 displays - 3

Last part in this series about building a clock with four HP 5082-7300 displays controlled with an Arduino.
After using the HP 5082-7300 desk clock for a whole day and night I came up with few improvements.
First of all, during the day nobody will look at it; why keeping it running, then? The are many ways to control it via software, like switching off the display according to the time of the day, to the room brightness, to a physical presence and you can certainly come up with other ideas. Instead of developing a software solution I will add a switch to control DC power to the whole circuit.
Meanwhile I wrote and applied some firmware updates. The first refinement is meant to reduce heat production, which occurs during the day when nobody looks at the clock: cut in half the display brightness at the higher luminosity levels. It does have an effect since the top of the box is not warm anymore. Then, since every digit has the decimal point, the new firmware moves around the dot endlessly instead of just blinking the central one. Third and last change was to read the LDR value once a second instead of once every PWM loop: this makes the loop a bit faster (ca. 0.1 ms) thus reduces flicker.
A further improvement could be to add some hysteresis and averaging to the intensity control, not counting adding further digits.

The firmware is available on github. Homework: are there other functions I have not described in these three posts?

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