Temperature measurement

Reading time 2 minutes

A temperature measurement can be useful for different reasons: whether it is the cold or hot water temperature, the generator temperature or that in the doghouse in the rear garage, there is always a need for control somewhere that can be implemented via SmartHome.

Almost 99% of all components work with two AA batteries, which need to be replaced at regular intervals, including the Homematic temperature difference sensor HM-WDS30-OT2-SM-2. Apart from environmental considerations, the battery is usually empty at the most inopportune time. We know the phenomenon of the flashlight, which, when you need it, emits just a glow at best. Murphy sends his regards...

Consequently, the question is whether you can simply use the 12V on-board voltage in the motorhome. With a DCDC converter This can be implemented quickly from 12 V to 3.3 V.

implementation

Take a soldering iron, solder, wire strippers and a Phillips screwdriver. Open the transparent housing cover of the temperature difference sensor by loosening the four Phillips screws, loosen the four nylon screws that hold the cover plate and also loosen the nylon hexagon spacers by hand. Finally, the screw connection of the cable bushing is loosened and the sealing rubber is pulled out of the PVC clamps in order to keep the cables freely movable.

Now the circuit board can be lifted out of the housing. On the back, the plus pole is located on the battery holder at the bottom left when the LED and button are also positioned on the left. Above this is the negative pole on the upper battery holder.

The DCDC converter has four connection cables: red and black for the 12 V input side, yellow and black for the 3.3 V output side. The black cables are each negative.

Consequently, the yellow cable is soldered to the lower positive soldering lug and the black cable to the upper negative soldering lug. The red and associated black cables are led out through the cable gland.

The sealing rubber is also pushed over the two cables into the clamping device and tightened with the screw connection.

The circuit board is placed back into the housing and secured with the four nylon screws. The DCDC converter finds its place in the battery holders, where the two plastic tabs are bent inwards. Since they are soft PVC, they only bend over but do not break off.

If the sensor has already been trained on the control center, the transparent housing cover can now be placed back on the housing and screwed on.