I am using the circuit proposed on this thread
I am using the Op Amp MAX4424 because it's what I had, the circuit is working almost fine, the only problem is that the sensitivity is very high, even touching the MPU with my hand it triggers the interrupt.
My question is how can I set up a lower sensitivity using that circuit? perhaps reducing the 20M resistor to a lower value?
Adjust the value of the 20M feedback resistor?
Edit, You might want to increase/decrease the value of the 10K resistor to GND.
The idle voltage output is setting too close to the trigger point.
The INT pins are HIGH and triggered LOW, correct?
ok, so changing the 10K resistors with a lower value will decrease the sensitivity, right? The INT pin are triggering LOW correctly, but as I told before it's extremly sensible.
Not both, just the 10K to GND. Change it to a higher value, like 20K. That will move the idle voltage up. It will need a stronger input to trigger the interrupt.
Then you have a wiring error somewhere.
What is the voltage V+?
Do you have the circuit ground connected to arduino GND??
Change R130 to a higher value. See how that does.
What is MPU_B?
Where is the ground connection?
What arduino are you using?
MPU_A and MPU_B are the two magnetic pickup wires.
There is no ground connection to the Arduino!!
What Arduino are you using?
OK. Change R130 and see how that does.
With R129 and R130 both at 10K, the idle output switch point will be V+/2, or 1.65v. That is right at the trigger point. Any input will trigger the interrupt.
You can change the resistors all you want without a Ground connection it will never work
do you mean the one of the wires (MPU_A, MPU_B) has to to grounded?
I am using a esp8266.
No the the symbol with GND below it needs to connect to the ESP GND
GND is is connected to ESP GND.
But looking at your comment I tighted MPU_A to GND and now it's all working perfectly. no false interrupts anymore and all is working as expected.
Not knowing anything about your magnetic sensor, I can't say that is the correct thing to do but if it works the way you want, OK.
I picked up a generic car magnetic sensor that's offen used on the fly wheels.
Does the MPU can damage (eventualy ~70V) the Op Amp or the signal it's 100% clamped and safe at the Op Amp input?
If the op amp is powered by 5v and the op amp input is clamped, you're good.
Only on the negative side. You still have 70V positive that will damage the opamp
Have fun
