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Digital clock - light variant

Mfhotkowski

Apr 28, 2014
1
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Apr 28, 2014
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Hi everyone, new here.

I'm working on an electronics final project for on of my physics courses. We've made a clock from a signal counter that counts from 00:00:00 to 23:59:59, with nothing but drivers, counters, seven-segments, and lots and lots of wires, it's quite a mess, but it works, and counts fairly accurately.

We want the seven-segments to brighten as the room the clock is in gets brighter, via a photodiode (pdb-c156). With the photo-diode being a current source, we tried using a transimpendence amplifier, but the change relative to light was very slight (this is before we put it into our clock circuitry).

Long story short, we need to use a current source photo-diode to make a +1.6 V powered load to a +1.9 V.

Also, not sure if I understand the adding of two DC voltage sources.

Thanks a lot for all the help!
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Joined
Nov 28, 2011
Messages
8,393
Hello and welcome to Electronics Point :)

Can you post the schematic that you tried, and the range of output voltages you were getting from it?
 

kpatz

Feb 24, 2014
329
Joined
Feb 24, 2014
Messages
329
Is there any circuitry in your clock to control the LED brightness now? Or is it just controlled by current-limiting resistors? Also, is the display multiplexed?

The simplest way to modulate the brightness with with PWM. If you can have the photodiode control the pulse width of a signal, you could modulate the display brightness that way.
 
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