Anolog Comparision - Resistor ladder circuit

[jey11]

Hi,
I need to build a function box for testing switches(Resiter ladder).
One input 2V or 6V or 8V .
The output should green led for 2V input.
The output should red led for 4V input.
The output should yellow led for 8V input.
All off for no input is selected.
How can I do this? Please help me out.

Jey

 

[Prototyp_V1.0]

HI. You just use three independent comparators to do that.

 

[jey11]

I tried It didn't work as it suposed to be.

for ex:
For 2V.. I compare with Vref= 1.5 if it is true turn on green led.
For 4V.. I compare with Vref= 3.5 if it is true turn on Red led and green led
For 8V.. I compare with Vref= 7.5 if it is true turn on all leds.

look like I am missing some logic here..

Only one common input is available...

 

[Prototyp_V1.0]

Hi. Use some simple logic gates between the comparator outputs to make only one output be active at a time.

 

[jey11]

Thanks for your help

 

[KJ6EAD]

This would be a good place to use an LM3914, although you don't need all 10 outputs. **broken link removed**
http://www.transkommunikation.ch/dateien/schaltungen/diverse_schaltungen/miscellaneous_circuits/Using%20the%20LM3914-6%20LED%20Bargraph%20Drivers.pdf

 

[jey11]

attached is the actual switch.

Thanks