I need a circuit in which a green LED will turn on only when the voltage is in between 1V - 3V. The voltage may change within the range of 0V - 5V. Can anyone help me with this task?

 

yes i can with micro ADC or comparator

 

How would the circuit scheme look like if you used a comparator?

 

have you used microcontroller

 

Yes, but I don't know how to ensure that there is a minimum of 1V and a max of 3V in the system. I don't know how to make sure that the LED works only in that area.
There is a random amount of voltage always flowing between 0V and 5V

 

How would the circuit scheme look like if you used a comparator?

DO YOU KNOW VOLTAGE DIVIER?

 

Yes, but I don't know how to ensure that there is a minimum of 1V and a max of 3V in the system. I don't know how to make sure that the LED works only in that area.
There is a random amount of voltage always flowing between 0V and 5V

 

Yes that is a comparator but you need a window comparator

The voltages at the top and bottom of R3 define the window. In the example above, the LED is on when the In is above the voltage at the bottom of R3 but below the voltage at the top of R3.


For your case run the thing from the 5 volt power supply.

Is that enough for you to get started?

 

what is window comparator

 

It is a circuit with the same function as the circuit in post #8. Its output is low when the input voltage is between a lower and an upper limit. Or, you could design it high when the input is in the "window".

https://en.wikipedia.org/wiki/Window_detector

 

Yes that is a comparator but you need a window comparator

The voltages at the top and bottom of R3 define the window. In the example above, the LED is on when the In is above the voltage at the bottom of R3 but below the voltage at the top of R3.


For your case run the thing from the 5 volt power supply.

Is that enough for you to get started?

Are you sure about this?

If Vin is within the window, then IC1 is trying to drive its output to +15 V while IC2 is trying to drive it's output to -15 V. So what is Vout?

EDIT: Papabravo reminded me that the LM339 is open collector, so Vout is well defined for this case.

 

It is not clear what the supply rails are for the LM339, but it might interest some to know that the output is open collector. Vout will be at +15V when the LM339's output transistor is off. One might infer that the supply rails are ±15V, but that might not be the case. Further, the part has certain other restrictions on the input voltages for proper operation. The parameter of interest is called Input Common Mode voltage Range. IIRC if either input is within 1.5V or 2.0V of the supply rails the output could be inverted. This is a real gotcha of a thing to discover in production.

 

It is not clear what the supply rails are for the LM339, but it might interest some to know that the output is open collector.

Ah! And I knew this, too. But simply forgot. Apologies to Dick.

 

Here is the thread, almost 10 years old, in which I was "schooled" in this matter.
It was the best lesson I ever learned from this forum.

http://forum.allaboutcircuits.com/threads/device-behavior.2270/#post-15152

In case anyone was wondering, we dodged a rather large bullet and things turned out OK.
Thank you Ron H, thank you masked man!