Bargraph Display help?

[Joesnow]

Hi
I'm making a circuit for a project... for the output ive got 20 LEDs controlled by two LM3914 chips... the output form my amp is from 0-2.5V, this progressively lights the LEDs untill all 20 are lit giving me 20 steps between 0-2.5V

What I'm after is if anyone knows a circuit or different chip that will allow me to have the two banks of 10 LEDs seperated into tens and units so that i could have 100 steps?

e.g.

Consider two banks of 10 LEDs with a scale 0-100 (0=ON and o=OFF)

0000000ooo oooooooooo (what ive got now) output = 35

000ooooooo 00000ooooo (what im after) Output = 35

The output of both is 35 but im just after more accuracy? I cant find a circuit diagram anywhere or a chip that will do this?

On the other sugested applications bit of the LM3914 it says that it can:

• 10-step (or multiples) programmer
• Multi-step or “staging” controller

Is this what im after? and does anyone have a circuit diagram for it?

any help would be much appreciated as im a mechanical engineering student with little knowledge of electronics

 

[audioguru]

Are you measuring the loudness of "the output from your amp"?
Then you should use one or two LM3915 logarithmic audio bargraph ICs.

The LM3914 is a linear voltmeter IC. It has steps that are very far apart at the bottom and the steps are very close together at the top.

The LM3915 has equal spaces between all its steps and its total range is greater. Each step is double or half the power, which is a small difference in loudness.

 

[Joesnow]

Hi sorry I’m making a device to measure torque on a rotating shaft. So I’ve got two strain gauges connected to a wheatstone bridge, the voltage difference is going through a differential chopper stabilized op amp and the output from this is connected to the input of the Bargraph circuit. So I was after a way of reading the torque from 0-100Nm from the rotating shaft and these lights would be seen as bands of light.
I’ve got the gauges, the wheatstone bridge and the amp all working and they are giving me voltages from 0-2.5V and I’ve got the 20segment bargraph working from a variable power supply and that’s working from 0-2.5V but I haven’t connected the two together yet so I don’t know weather the bargraph display I’ve got is linear?
I though the LM3914 lit LEDs up in linear steps?

Does this mean I need the LM3915? And will that fit pin for pin with the LM3914?

Also do you know if it’s possible to with the LM3914/5 chips and how I would set this up for 100 steps with still 20 LEDs?
Or would I need a different chip? And what would I need?

Thanks

 

[hjames]

LM3914's and the like are setup to do a single bar display with relatively low accuracy. You need something with an 8 bit ADC, and a binary to decimal converter. Plus, it would make more sense to go with a 2 digit LED display instead of decade counter style. The easiest way is to use one of the entry level PIC based development tools - or other microcontroller. (This could be done without a uC, but it would take a pile of legacy parts, and would definitely not be easy).

Or just buy an off-the-shelf panel indicator for $20...
**broken link removed**