I'm currently trying to build a device to measure the impulses sent from my electricity meter. I've built the sketches and it works fine, it can detect a flash of light, but on my meter, it doesn't detect anything. After reading the manual of the meter I'm starting to think it's an IR light source rather than just a red led as they describe.
Is there something that I can do to my photoresists to make it detect IR flashes? or is there another device like a photoresistor I can use in place of it?
Mine flashes in a visible red colour, but the flash is very brief.
A detector would need to have quite a fast response time to see mine. That would rule out a Light Dependent Resistor. A Phototransistor is faster and a Photodiode faster still.
@JohnLincoln from what I can read in the document of the "EFR SGM-C4 Meter" it says the light should blink for 80ms each time. I created the sketch to just output the light level continuously to grab this. It works flawlessly when I flash a torch light over it and responds instantaneously. I assume if it was just a flash for 90ms it would register. Sensor is a bog standard 5506, GL5506 LDR.
@TomGeorge I thought of this too, but most modern phones have an IR filter now. I tried everything, might have to dig out an old Nokia from the depths of the basement
No. Use a photodiode, or in a pinch an IR LED in photovoltiac mode.
IR LEDs are wavelength sensitive when used as photodiodes, and there are two popular wavelength ranges, ~850 and ~940 nm. Try one of each, keeping in mind that the optimum response is to light with wavelength 25-50 nm shorter than the LED emission peak.
The " OSRAM Fotodiode TO-39 1100 nm 55 ° BPX 61" for 12,60 Euros would work fine, but seems a bit expensive.
If the flash duration is 80 ms, you may be able to use the Arduino analog read function (use the internal 1.1V AREF) with the naked diode in photovoltaic mode. Note the "reversed polarity" compared to the diode symbol:
Otherwise, you may need an op amp transimpedance amplifier:
You may need to adjust the values to suit your photodiode, but I have had this working for about 3 months now with no issues. Almost any small signal npn transistor will do.
I've tried with a red LED as detector without success.
Fill in some details - what arduino module you are using, what outcome you want etc.
I'm logging monthly data to spiffs, reading with ftp, and displaying results on a web page.
I’ve “ obtained” one of these . Included here to show the meter usually has a magnet so this device will just hold in place and stop outside light .
There is a visible led ( on mine 1pulse = 1/100 KWh) and an IR pickup for programming the meter .
Sorry for the delay in getting back, Im still waiting the delivery of the photodiode, but in the meantime, I managed to find an old phone and find the ir output, which ill be honest confused me.
I was expecting the "3 - LED Impulskonstante" to flash the usage, but with my phone I can see the IR flash on the second LED on group 5. I also tried it with the photoresister and it actually picks up the flash.
I assume that's actually correct as the device @hammy suggested would connect on point 5.
So whats point 3 for?
Ive also updated the current setup to be a nodemcu board + 10k resister and photoresister (partly for the wifi connection) This then sends the data to influxdb which I can then graph via Grafana.
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