Using a voltage comparator to raise an interrupt

Other Hardware General Electronics
1

Hi everybody.
I'm trying to use the LM2903 voltage comparator to produce an interrupt on my Arduino Nano when a given voltage become higher than a reference.

Before trying to generate interupt, I've taken a look on how the LM2903 work. So I've made a circuit that read the 2 inputs and the associated output of the LM2903. It work correctly :

  • 0 as output when when Input < Reference
  • a value when Input > Reference

The problem I've is the following one :
When I decide to connect to an interupt pin on the nano, I'm not able to detect a RISING or FALLING edge on my signal.

Any ideas ??

I've attached the information on the first circuit.
The circuit for the interupt is nearly the same : I've just connect to pin 2 or 3 of the Nano.

LMx03_01_sch_eagle.png
LMx03_01_sch_eagle.png2090×1057 21.5 KB

Using LM2903.pdf (255 KB)

2

Have you tested your software with a simple switch circuit connected to the same pins?

3

I guess you have to pull the trigger high (say 10K) because the LM2903 is open collector output.

4

An analog comparator with an interrupt is built into the AVR-based Arduinos.

5

The LM2903 comparator has an open drain. Have you supplied the necessary pullup resistor?