Detect state of valve

Hi forum
I’d like to monitor my central heating which is of older design (therefore: no suitable interface for directly grab data). My idea is to simply detect the status of an electronic valve which is only open, if the heating is on.
Using a sensor-debug-app on my android i can see magnetic change if it’s on. But using a 49E-hall sensor did not result in any usable data.

Any suggestions on how to get useful data?

Thank you very much in advance
Chris

The sensor in your phone is way more sensitive than the 49E sensor.
If the valve is a solenoid type powered by alternating current then you'll need to place the 49E sensor right on top of the solenoid coil and take measurements at about 500 times per second.

Why not strap a temperature sensor to the boiler outlet pipe , if it’s hit the boiler us running

If the solenoid is AC powered, a current transformer could be used to noninvasively detect current flowing in one wire to the solenoid.

mikb55:
The sensor in your phone is way more sensitive than the 49E sensor.
If the valve is a solenoid type powered by alternating current then you'll need to place the 49E sensor right on top of the solenoid coil and take measurements at about 500 times per second.

Is there something - with a reasonable pricetag - which is close to what my phone can measure?
I will have to dig deeper into the topic in order to answer your other questions. But my amateur-look at the phone-graph tells me it is ac-powered... I'll try to figure out

hammy:
Why not strap a temperature sensor to the boiler outlet pipe , if it's hit the boiler us running

I might have not been clear about this. I already do this to measure not only the true runtime of the boiler but also the temperature. But measuring the valve would help me calculate the amount of oil used by the boilers (it's actually two, but thats not important.

Thanks for your inputs, i'll continue my research on the devices used and the sensors needed :slight_smile:

What is the valve's voltage? AC or DC?

Shooting blind:

Use the signal which turns on the valve to instead drive a DPDT relay with characteristics *similar * to those of the valve. One set of relay contacts drives the valve, the other provides a switch closure indicating valve operation.

If you're doing this project to measure fuel consumption and you don't need real-time annunciation of the state of the valve, you might consider using an SD card module and logging the state of the valve over time. You can do like jremington said and take a line from the voltage-in to the valve and transform it down to 5vdc into an I/O pin on an Arduino. Power goes to turn on the valve, and the arduino gets a 5vdc HIGH input signal. This can be logged into a text file on the SD card with a time stamp. Then when the power is turned off to the valve, that can be logged with it's own time stamp. You'll have the time between your valve opening and closing for as many days as you feel like logging, and now all you need is to know your flow rate of your fuel oil. Keep in mind that with many fuel oil boilers, the amount of fuel going through the valve is not equal to the amount going through the nozzle and being consumed by the boiler. If there's a bypass nozzle, some fuel oil is recycled back to the reservoir tank if your boiler is a low-fire start / high-fire run boiler or similar setup.