Hi there.
I have a project to complete, in which I need to have an increasing resistance (using a potentiometer), which will then light up 4 LEDs after each other. For example, if the pot starts at 100 ohms, the first LED is on. The pot increases to 500 ohms (exact values are not important), the first LED switches off and the second LED switches on.

I've attached my circuit diagram for how I thought to solve this, but it doesn't seem to work. I'm guessing the tolerances of the resistors are at least part of the issue, but I may be wrong. Any advice on how I may solve problem, or what different approach I should be taking?

 

So you have described a circuit which must perform 3 functions: sensing, switching, & extinguishing.

SENSING is related to the position (resistance) of a potentiometer indicating that a voltage or current threshold has been crossed.

SWITCHING must turn ON an LED when a threshold has been crossed.

EXTINGUISHING must turn OFF LEDs lower in the chain.

Which of these functions are inherently analog, and which are digital? What components can you select from to implement each of the functions?

 

Have you considered using "Window-Comparitors" rather than using Gates ?
.
.
.

 

What subject is it for?

i.e. Are you expected to use op amps, logic gates, or just transistors?

 

Are you allowed to use a micro-controller?

 

An LM3914 IC lights up LEDs one after the other depending in the voltage input.

 

An LM3914 IC lights up LEDs one after the other depending in the voltage input.

The TS was asking for homework help, I think that they were asking how to design a simple circuit. I'm not sure what devices that they were allowed to use, as they seemed to be using mixed with no op amps

That being said, reading through that datasheet will show the TS a very good way to do what they want if they can use op amps!

 

The LM3914 uses comparators, not opamps, but a circuit using opamps will work.