Measuring Gas with Hall Effect Sensor

borpin · 2019-02-24T21:22:38.605Z

monitoring pulses using a Hall effect sensor on a gas meter

Please, tell me more. I have tried this on several occasions without success.

cjenkins · 2019-02-24T21:45:21.947Z

I used an emonTH v2 with one of these:
https://uk.rs-online.com/web/p/hall-effect-sensor-ics/8855388/

I have a 100 kohm resistor between GND and pulse input and a 10 nF cap between GND and vdd. I extended the sensor on about 1ft of flying lead and used a multimeter across the resistor to find the ideal location for the sensor (currently held in place with tape) where the voltage across the resistor drops from ~2.4 V to 0 V for about a quarter turn of the dial. When my boiler is running at full (heating/hot water) I get about 5 turns of the meter per minute which works out at about 30 kW power. So when I run the gas hob I get about one turn every 2 or 3 minutes, so the power consumption looks like a 6 kW sawtooth when in reality it should be ~2-3 kW constant load. Not perfect, but a big step forward on twice monthly meter readings.

Let me know if you need any more details.

borpin · 2019-02-24T21:51:05.160Z

EmonPi and Smart Meter Readings

Let me know if you need any more details.

Please!!! What sort of meter do you have?

EmonPi and Smart Meter Readings

I used an emonTH v2 with one of these: https://uk.rs-online.com/web/p/hall-effect-sensor-ics/8855388/

I’ve got a strip of them sitting here!

EmonPi and Smart Meter Readings

I have a 100 kohm resistor between GND and pulse input and a 10 nF

That is where I start to get lost. Capable of following a wiring diagram, but what the bits actually are doing is a mystery to me.

I’d really want to use a Pi or a D1 Mini I have lying about.

Photos?

(I’ll split this to a new topic).

Vster · 2019-02-25T12:05:18.627Z

I’m interested in this too, but for reading my water meter.
Just checked eBay - wow. £3.49 each, or 10 for £4.20 from RS. Shame I only want 1!

As for the circuit, is it something like this?

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borpin · 2019-02-25T12:51:34.378Z

Vster:

As for the circuit, is it something like this?

Does that take account of Pi inputs being 3v3 and not 5v tolerant? (yes I’ve blown a Pi input up…)

Vster · 2019-02-25T12:54:25.693Z

Hi Brian,
I’ve not built it, that was @cjenkins.
But looking at the spec sheet -

To support portable and battery powered equipment the
design has been optimized to operate over the supply range
of 2.5V to 5.5V and consumes only 24uW with a supply of 3V.

I’d say it would be fine.

Robert.Wall · 2019-02-25T12:56:06.799Z

You could buy 10 and sell 9 here at £3.48 each?

The circuit looks wrong to me. Have a look at the data sheet: RS Components International
This shows the resistor as a pull-up and the capacitor across the supply for decoupling.
And the data sheet:
under Recommended Operating Conditions
Operating conditions: 2.5 V min - 5.5 V max.

borpin · 2019-02-25T12:58:03.382Z

Vster:

I’ve not built it, that was @cjenkins.

Hi Lee, yes, sorry I got that. I also note he built it on an EmonTH so probably 3V3 input. It is one area I’d love to make work so I can see how much gas is needed/used for various situations.

Vster · 2019-02-25T13:16:10.000Z

Robert, you are as usual correct.
I was following @cjenkins description, where he’s (incorrectly!?) using a pull down rather than a pull up.

removed diagram to avoid confusion

Also, AH180’s going cheap, any one interested!?

Robert.Wall · 2019-02-25T13:19:44.456Z

Except you’ve now got your wires crossed!

[Edit]
If you look further down the data sheet, the reason for the capacitor across the supply becomes clear. It appears to turn on and sample the magnetic field for 100 (± 25) μs every 100 (± 25) ms, so the capacitor is there to ‘smooth out the edges’ and supply at least part of that current pulse.

Vster · 2019-02-25T14:33:19.679Z

Robert,
And that’s why you shouldn’t doodle during conference calls…

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