Seven Segment Display
Categories: [ Science ]
I recently discussed with a friend how to read with a computer the 3-digit numbers from a device using seven-segment displays. One solution we came up with was to put a phototransistor in front of each segment, read the seven on/off signals and recognize the digits. I then wondered if it's possible to use less than seven phototransistors per digit.
A minimum of four segments is obviously required, but after a bit of computer-aided experimentation, I found out that only 5 segments are enough: if you remove the lower and the lower-right segments, you can still identify all ten digits.
So with only 15 inputs instead of 21, you can read the 3 digits, using a 16 bit I/O expander (e.g., a MCP23017; this one even has internal 100 kΩ pull-up resistors, so it may be that nothing else than the phototransistors is needed).
[ Posted on March 5th, 2013 at 22:19 | no comment | permanent link ]
