T0NY

seven segment display adjustment
« on: October 20, 2012, 06:34:52 PM »
Hi everyone, I have a digital thermostat that will only read between 30 - 45C. I want it to read between 20 - 35. The thermostat itself has had all the I.C. names scrubbed off and I cant get into the firmware to adjust the span. My thought was that if I disconnect the feeds to the first seven segment display and route them through some kind of logic circuit I could change the reading from a 3 to a 2 and from a 4 to a 3. I then can adjust the probe off-set to compensate for the change in reading. Does this sound do-able?


audiomixer

Re: seven segment display adjustment
« Reply #1 on: October 20, 2012, 07:15:02 PM »
thermometer, not thermostat i suppose....

your scheme sounds rather complicated.... adjusting 2 to 3 is one digit, 3 to 4 some others, other readings would be completly off. you would still need to inculde a check of what digit is to be displayed (maybe segment E can be used for that...) well acutally that would be an option:
check segment E
on: light up segments E, C, F, D according to truthtable A
off: light up segments E, C, F, D according to truthtable B

where is the probe, what probe is it? maybe is easier to trick it there... or build a simple arduino based one.

- michael

T0NY

Re: seven segment display adjustment
« Reply #2 on: October 21, 2012, 12:19:26 PM »
thermometer, not thermostat i suppose....

your scheme sounds rather complicated.... adjusting 2 to 3 is one digit, 3 to 4 some others, other readings would be completly off. you would still need to inculde a check of what digit is to be displayed (maybe segment E can be used for that...) well acutally that would be an option:
check segment E
on: light up segments E, C, F, D according to truthtable A
off: light up segments E, C, F, D according to truthtable B

where is the probe, what probe is it? maybe is easier to trick it there... or build a simple arduino based one.

- michael

No its a thermostat, it controls the temperature in an incubator. I know its easier to install a new thermostat however this unit has humidity control and turning control all built into the same panel so i'd like to keep it if possible.

Segment E & C are my biggest hang ups as they need to be swapped over for the two different digits 2 & 3. My first thoughts were to use segment F as a signal to some kind of solid state switch or relay but I cant find one with NO/NC contacts that operates at lower enough power.

A different probe would make no difference as the stat only starts its reading at 30 so I have to physically alter the first segment.


 

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