I've added an extra sensor to my flukso, to monitor my water usage. The watermeter (a Sensus 620) has no digital connections, and has no built-in magnet for a reed-relais. But it has a turning red/metal wheel inside, that is detectable with an optical sensor. Such a sensor is for sale for  € 90,-, but that's too much for me, some browsing on the internet gave me this:

A TCRT5000 Infrared Reflective Photoelectric Switch Barrier Line Track sensor (bought at Ebay from China for about € 1,50), an home-made wooden sensor-support, a resistor of 100 ohm to obstruct the flow of current just a little, an old ISDN kable, some shrink sleeve and behold:

The wooden board has three holes, one big square one just over the wheel, two round (5 mm) ones that fit over the pegs on the watermeter, keeping the sensor always in the same place. At the first picture you can just see the wheel through the square hole. I attached the sensor with a screw to a little piece of wood, aimed an tested and then glued it all together. Later on I attached the cable with a tie-wrap going through the square hole, also compensating for the height difference between the glass and the grey rim.

The sensor has two leds, a red one to indicate power and a green one to indicate the digital pulses.Sensus 620 watermeter

Hooking up was easy, with some help on the forum. I now see data flowing, I still have some challenges left:

1) Lining up the sensor wth the little red/metal wheel. In syslog I see the pulses, but sometimes it fails ... ...

2) Getting the data to flukso.net and making some sense out of it. I see spiking graphs, but they still seem wrong somehow. A reboot and some time might help. Testing was easy, just draw a bucket of 10 liters of water and check the pulses. Later on I checked the pulses in syslog, the pulses with MQTT and the rotating dials.

3) A protective cover over the sensor, to protect it from dust and falling objectsTCRT5000 IR optische sensor.     

4) Gather the data locally . (MQTT, syslog, http, expect ..  I'm not sure yet.)

Changed later:
- A little piece of Scotch Magic tape taped to the little round knob over the red/metal wheel, to take away the glare. This way I didin't have to sandpaper anything.The tape was the most expensive of all, the sensor is less than € 1,50, the resistor € 0,10.
- made a cap over it all, just a lid of something.
- moved the connection from port 2 (analog or pulse) to port 4 (pulse only). It works flawless now, probably a faulty connected wire gave some fake pulses..

results now (Flukso website):