Just learning

Discussion in 'The Projects Forum' started by gandalf0531, Aug 29, 2008.

  1. gandalf0531

    Thread Starter New Member

    Aug 26, 2008
    I am just learning about electronics, and want to build a digital meter using an LM3914 IC and a bargraph to measure dc voltages from .01 to 1. I found several schematics and this one seems to be the simplest. Do you think it will work?

    Also, I have read the data sheet for the LM3914, and I still don't understand if I can change the signal in range to measure different voltages. Can I do this??

    Thanks for any help!!
    Last edited: Aug 29, 2008
  2. iONic

    AAC Fanatic!

    Nov 16, 2007
    The Signal Pin (Pin5) will take a max of +/-35V, so you would be restricted in that sense. But by using a SPDT switch and changing the resistor values of R1 and R2 by a factor of 10 you could switch to a scale of 1 - 10V. y using a multi position rotary switch you can have several scales. you can also cascade the LM3914's to increase the scale range or resolution... 0 - 2V in .1V increments or 1 - 20V in 1V increments, or even 1 - 10V in .5V increments... You can cascade them for up to 100 elements. The data sheet shows you how to cascade. But you would realize that by doing all thus you will wind up with a crude meter for same from of a decent digital meter measuring anything from AC to DC to Capacitance, Resistance...

    So for the sake of learning I would stick to a 1 or 2 3914's and a DPDT switch.
    Last edited: Aug 31, 2008