Hello,
I found about 20 of these 2.75" tall clock type 7 segment displays in a very old box - early 90's era. I performed some basic testing to determine pin outs and built into a circuit. Unfortunately the display is very dull. Please lecture me here about not doing my homework properly, lol. So I actually did more testing. Here is the set up and results. My digital meter is broken, so this was off an analog meter. Vs was from various bateries.
So from what I can tell, each segment needs about 5.6 volts. Each segment contains 3 red leds. So back to my circuit driven with a MM74HC4543, which works well, except, well it's dull.
So, I tried removing the current limiting resistors. At 5.4 VCC it is minimally acceptable in brightness. Ok, so it's acceptable in a dark room. My question is what would happen if I put 8 Volts or so to the display supply, but keep rest of circuit at 5 Volts?
The 4543 is sinking when a segment is on (phase pin high). I just don't know about input gates on chips and what 8 volts when chip is at 5 volts will do? Also could 8 volts somehow corrupt or leak to the 5v and fry everything else?
Thanks for your help and time.
Rich
PS: http://pdf.datasheetcatalog.com/datasheet/nationalsemiconductor/DS005128.PDF
I found about 20 of these 2.75" tall clock type 7 segment displays in a very old box - early 90's era. I performed some basic testing to determine pin outs and built into a circuit. Unfortunately the display is very dull. Please lecture me here about not doing my homework properly, lol. So I actually did more testing. Here is the set up and results. My digital meter is broken, so this was off an analog meter. Vs was from various bateries.
So from what I can tell, each segment needs about 5.6 volts. Each segment contains 3 red leds. So back to my circuit driven with a MM74HC4543, which works well, except, well it's dull.
So, I tried removing the current limiting resistors. At 5.4 VCC it is minimally acceptable in brightness. Ok, so it's acceptable in a dark room. My question is what would happen if I put 8 Volts or so to the display supply, but keep rest of circuit at 5 Volts?
The 4543 is sinking when a segment is on (phase pin high). I just don't know about input gates on chips and what 8 volts when chip is at 5 volts will do? Also could 8 volts somehow corrupt or leak to the 5v and fry everything else?
Thanks for your help and time.
Rich
PS: http://pdf.datasheetcatalog.com/datasheet/nationalsemiconductor/DS005128.PDF
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