Wiring an LED Bargraph to act as a meter

[KypDurron]

Quick question...I was wondering if there was a way to take an LED Bargraph and connect it to a knob, so that depending on the turn of the knob, a different amount of LEDs on the Bargraph would light up? If it helps, you can think of it as a volume control meter display though that is not what it will be used for. I am having trouble figuring out how to get voltage to the different pins for the different LEDs at the same time based on some type of turning knob. If anyone has any thoughts or knows of any other components that would be better to achieve this goal that would be greatly appreciated. Thanks!

 

[ScottyUK]

Investigate the LM3914, LM3915 and LM3916 driver ICs. They take care of the display interfacing.



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If we learn from our mistakes,
I'm getting a great education!

 

[KypDurron]

Any advice on where to get these? It does not seem like I can find them at any standard store. Thanks!

 

[ScottyUK]

LM3914 available from RS Components in the UK.

Also have a look at M5450B7 from ST Microelectronics, available from the same source.



----------------------------------

If we learn from our mistakes,
I'm getting a great education!

 

[mrkenneth]

You can also probably get a sample from National, depending on your location. The different varients are for the voltage levels (LM3914 is linear, LM3915 is log, and LM3916 is "extended".)

 

[jims99]

I agree that LM3914 is the best way to go. One can always duplicate the circuit by using a few quad comparators (e.g. LM339) with a string of series voltage-divider resistors. Reference: the LM3914 data sheet:

http://www.national.com/ds/LM/LM3914.pdf

and go to page 6.

jim

 

[hrc]

MANY years ago, and I may still have a few, used a bar graph unit with the National chip on it, essently just an analog voltage bar graph. Not sure if they still exist, it was around 15-20 years ago when I had them,

 

[KypDurron]

I tried the LM3914 and it worked like a charm..gave me exactly what I was looking for...thanks to all!