LED bar Voltage visualiser

Hi
I was interested in making a LED bar with 24 LEDs that would show a voltage output in 0.5 volts increments to a maximum of 12 Volts. I only want this to work with passive components... no microcontrollers...

any ideas? Circuit diagrams?

Thanks

A microcontroller isn't necessary.
Barring that... a bargraph driver IC or other semiconductors will be necessary.

I am not sure whether you consider a zener diode "active" or not, but you could use 24 of those to turn on each LED at a certain threshold. Each one will need a separate resistor value to keep the intensities the same. This won't work at less then about 1.5 V, though. No passive device will since you need to exceed the LED's forward voltage.

Cascaded LM3914's... the longstanding solution for this kind of display. Still for sale at Mouser.com.

pwillard:
Cascaded LM3914's... the longstanding solution for this kind of display. Still for sale at Mouser.com.

ditto..

I think they can handle up to 10 leds each IC?

I would try ebay first..usually cheaper!

I was thinking more in terms of resistor network... or something very passive...

any ideas?

You could simply string a bunch of voltage dividers, but it won't "snap" on and the low voltage LED's will be much brighter at 12 V than the higher voltage ones.

And, again, it will be impossible to light LED's when the source voltage is less than about 1.5 V.

FardinB:
I was thinking more in terms of resistor network... or something very passive...

any ideas?

Yes, you can use resistors for voltage divider part. But, there is no way you're going to be able to turn on an LED at voltages under the LED Forward Voltage (usually 2-3v depending on spec, brightness, color, etc) without some sort of transistor or op-amp.

I'd suggest googling "Passive VU Meter Schematic" (maybe throw a "DIY" in there too) and the like. Click on the 'image results' in google and scroll through to get an idea what others have done.

Can I ask why you want to be so "passive" about it? What's your reason for not wanting to use semiconductors? (No judgement, just curious.)

FardinB:
Hi
I was interested in making a LED bar with 24 LEDs that would show a voltage output in 0.5 volts increments to a maximum of 12 Volts. I only want this to work with passive components... no microcontrollers...

any ideas? Circuit diagrams?

Thanks

24 Transistors with different resistors on the base of each, to represent the voltage level?.. that's 1 way, and plenty more...