# Old magazine series 99 IC projects

#### ratstar

Aug 20, 2018
485
In the 1979 one, I see a gizmo for a bar graph, and someone needed one for his water tank not long ago. =)

It works with a strange technique of dropping voltage through diodes, but I dont see how it works entirely. Its actually an ADC! but you need one bar per bit, not one bit per power of 2 of the result, goes to show if all you need is 8 bit resolution ADCs sample as fast as you want, as long as you put the full 256 lines down.

#### bertus

Moderator
Nov 8, 2019
3,034
Hello,

Did you read the text of the led bar graph?

When turning up the voltage, led 6 will be on first, then about 0.7 volts higher led 5 will turn on etc.

Bertus

#### ratstar

Aug 20, 2018
485
I see, I was thinking it was a current dependant input! i see now. cool.
You can exchange the diodes for voltage dividers, if your short on semiconductors.

So does that mean you just put a current divider instead of a voltage divider you get the current version!?

#### Nanren888

Nov 8, 2015
622
It works with a strange technique of dropping voltage through diodes, but I dont see how it works entirely. Its actually an ADC! but you need one bar per bit, not one bit per power of 2 of the result, goes to show if all you need is 8 bit resolution ADCs sample as fast as you want, as long as you put the full 256 lines down.
Diodes used to set voltage thresholds is not an uncommon technique.
Here it would give a soft turn on, for each LED, I guess.
.
256?, OK with 256 LEDs, maybe 32,768 diodes, about 150 volts and 256 resistors, ratings for that voltage & quiite a lot of current.

#### ratstar

Aug 20, 2018
485
256?, OK with 256 LEDs, maybe 32,768 diodes, about 150 volts and 256 resistors, ratings for that voltage & quiite a lot of current.

Pure Parallel does increase power requirements - but it would potentially give you sub pico-second sampling, if you handled all the other problems, which I'm not aware of yet.

Moderator
Nov 17, 2011
13,337

#### TCSC47

Mar 7, 2016
117
Love these 99 cct books and others like them. When I was an apprentice and we were being taught valves (It was the 60s!) I got hold of a Practical Wireless, cct pocket booklet. I spent a lot of my time knocking up the transistor ccts and learning from them. Didn't get very good marks from my supervisors, but I found I knew a lot more about transistors than any of my apprentice colleagues.

#### ratstar

Aug 20, 2018
485
Didn't get very good marks from my supervisors
Maybe they were jealous.

#### TCSC47

Mar 7, 2016
117
Maybe they were jealous.
No, I just didn't realise that I was supposed to do as I was asked to! You get wallys like me everywhere! Lol! Took me a while to figure this out. Mind you it enabled me to walk straight into a job after my apprenticeship.

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