At the very start of this day, i visited the new office of Boemlauw and Dennus. When arriving at the office i noticed a nice system, people tend to use to open the door fromout their office. It was a basic Door Intercom.
After talking to Dennus for about 5 minutes, we got the idea to modify the existing Door phone, so we could remotely toggle the "Door Open" contact, which basicly is an "Bus Operated" N/O Contact. After having a nice tour through the new office i came to the point where i was thinking how to make the doorphone do what is was not meant for... at least.. not as it was sometime in the past designed for.
We pulled the phone of the wall and opened it up, Made a simpel scheme to bridge the N/O contact and put a relay on top of it...
Here you will find the scheme of the Door Intercom system [Golmar T910 Series]
After making up an shopping list, we went to visit DIL in rotterdam, and bought an 5V DC Relay, a housing to fit in all the gear a BC547 Transistor, a diode and some push buttons, DC jacks and a power supply.
After some very hard soldering work ( UTP just is not a good cable to solder these things with but hey... it was a crazy idea... so we had to use the things we had.
The finished product had an DC input, and a DC output with which we could power up an Arduino. and a trigger wire, which we could use to remotely switch the transistor.
After carefully modifying the Door Phone, we put everything together like nothing happened. But now with a hiddem switch/relay box in the closet right next to it.
Next time we will try to control the opening of the door with an Arduino via Ethernet.. and even via IR with a standard Apple remote ( since there where like 3 of them at the office )