I need to use an ESP32 (Node MCU variant i believe) to do some stuff when a voltage is read on some of its pins. It is to be used with my Oilburner for house heating, to measure its runtime and i noticed that when the boiler is burning i can get a voltage from an exposed pin. Reading this voltage I measured it at 3v which means the ESP32 should be able to read it directly. I did however still place a voltage divider in between just because my impression was that it could be good idea nonetheless.
Referencing the following image:
My R1 resister is 1k ohm and my R2 resister is 3,3k ohm. Those were the resistors i had at the time and my intention was to do something about it later.
However.. What I'm experiencing is that when the oilburner is burning, and 3v comes on from it, my ESP32 reboots, and the only thing i can think of is if the source voltage is somehow not correct and maybe overloading the pin, so i remeasured the source. Even though it was still 3v i noticed that my multimeter at first showed 6v at the moment the burner turns on. IF my multimeter is showing correct values, its like its peaking right when the burner turns on, which could be the cause of the reboot. Because afterwards as the burner is still burning, and 3v is output, the ESP32 is running without issues.
First of all. Since i only have a multimeter, is there a way for me to measure peak voltage, so that i can calculate the correct voltage divider needed for this task?
So, You had 3V with the red meter probe on the boiler output pin, where was the black probe? Did you check the voltage with the meter set on ACV as well as DCV? Think I would use an opto coupler isolator.
JCA34F:
So, You had 3V with the red meter probe on the boiler output pin, where was the black probe? Did you check the voltage with the meter set on ACV as well as DCV? Think I would use an opto coupler.
There is a negative pin on the boiler too, where i had the negative probe from the multimeter on, when measured..
I just tried what you suggested. I measured using DCV first, and this gave me 3.05v. Then i tried using ACV and to my surprise this measured 6v .. I wasn't even aware that was possible!
djda9l:
My R1 resister is 1k ohm and my R2 resister is 3,3k ohm.
Wrong way round? Best to choose around 10k for R2, and scale R1 to match - minimizes current drain without losing accuracy, and provides good input protection.
BTW did you check for no AC component on the voltage you measured? Multimeters on DC setting will not indicate anything about any AC component, even if its way larger than the DC value.
