LM3914 input selector idea


2012-11-18 7:47 pm
Greetings my audio friends, this is my first post here, so excuse me if I post on wrong place.

I was working on my voltage indicator and at the same time, I was building my 6-input selector switch for my preamp (push button type). And one idea cross my mind, while I was working. Why not use LM3914 as a signal source for input selection?

LM3914 is used as voltage indicator, with range 2.1 - 12V, in DOT mode. Voltages from LEDs are used for switching PNP transistors, for relay driving. And there you go - No clicking knobs, just potentiometer, which regulates from 2.1 to 12v. (there are few more components like two trim pots for adjusting range etc.) Depending on input voltage, you are selecting input. Interesting thing is that when you use BAR mode on LM3914, you can select multiple inputs, all of them if you need. Also you can use a digital switch IC, CD4066 maybe, for perfectly silent input selector (maybe adding a buzzer is a good idea)

And you can make up to 10 input channels. And you can adjust circuit for your own application, maybe as a step regulator for something, etc...

Btw, changing purpose for electronic circuits is my great pasion, here is schematic, simulated in Circuit Wizard. Waiting for comments. Enjoy!


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Paid Member
2007-09-15 8:14 am
Interesting idea :) One comment... the series 100 ohms across the 12 volt rail are very wasteful of power (and I suspect to low a value anyway). Maybe look at a couple of quad opamps used as comparators to drive the bi-colur LED's.

But yes... an unusual idea.


2012-11-18 7:47 pm

Thanks guys for comments, ideas and suggestions. Will play with this, maybe solving gofars issue with this thing. DUG`s idea is interesting, I will make a prototype. I am glad that you liked idea, since this is my first post here.

My main goal was to achieve digi-like, rotary encoder switching, but without, encoders, microcontrolers, etc. A simple knob would be a nice touch on front panel of amp or preamp, and to make others think that is digital ;)

Thanks again!


2010-12-09 11:53 am
The idea was also employed to "increase" the number of logic inputs for controllers wich incorporate an ADC. Have seen it used on some frequency counters with PIC. Prescaling, intermediate frequency offset, etc. was selected via a preset input voltage.