If you put a large resistor (>100K) between the pin you want to use for sensing and Vcc (battery voltage) then link one of the wires of the sensor to gnd and the other wire to the sense pin the circuit can then check for a change.

So if the window is shut then the sense pin will be Vcc if it’s open then it will be 0V

I hope that helps

Couple of things to think about with capacitors.

With electrolytic caps there ESR ( Equivalent Series Resistance) is quite high if you need a lower ESR try going for a polymer electrolytic.

Ceramic capacitors, as previously said don’t go for a capacitor that is rated at the same voltage, in my experience at least 1.5 to 3 times the max voltage your working with. So if your working with 5V I would go with a 16V part.

The reason for this is the DC BIAS of ceramic capacitors, if you need 1uF of capacitance and use a 6.3V cap the DC BIAS of the capacitor could only 20% to 30% of the stated capacitance. Therefore you would need 3 or 4 capacitors at 6.3V to get the correct capacitance where as with a 16V part you may only need 2 capacitors in parallel to achieve the correct capacitance.

Most good capacitor manufactures will have these online in the specifications area of there website.

Also be careful depending on the power supply your using they may need electrolytic as the ESR of ceramics is very low and this can cause the power supply to become unstable as the control loop of the power supply can’t cope.

These are lessons learned over the years as I alway say you learn more from making a mistake than being told what to do and getting it correct 100% of the time.

Hi All,

This is my first post on this site!!

Yes this is a really good project but for the UK controlling a light inside of a wall switch you would need to do the following.

Re-wire the ceiling rose as in the UK there is a live feed from the rose that is switched by the switch and then returns to the rose to the "switched live" See http://www.diydoctor.org.uk/project_images/lights_and_switches/ceilingroseb2.jpg

Put an extra cable up to the ceiling rose with the return cable from the board that goes to the switched live and add an extra terminal in the ceiling rose to link the neutral to the other side of the lamp fitting.

If the back box is metal, it would need to be changed to a plastic box , I wouldn't myself want to mount the board in an earthed metal box!!

As other contributors have noted there isn't any fusing on the live and neutral feeds if the SSR were to fail short because of a short circuit in the lamp or ceiling rose then there could be a large current going through board that could potentially cause a fire, safety is always the first thought with any mains electrical circuit.

I could see this board being used in a plastic box inline to a table lamp etc. but it would need a lot of work to re-wire your house if you intended to use it behind a wall switch.