This week's how-to is brought to us by special contributor Chris Turek, who would like to thank Rob Augusta for his help and electrical expertise.
My inspiration for this project: I walked up to my building and started pulling out my keys when the guy next to me pointed his cell phone at the front door and it buzzed us in. I was in shock. When I asked him how he did it he laughed and said he was actually just hanging up the phone with his girlfriend and she buzzed the door. I immediately realized what I had to do. I had to figure out a way for my cell phone to buzz open my front door.
My objective: To trigger the door buzzer in my apartment from a phone or more precisely, my cellphone. I began scouring the Internet. My first thought was an X10 device but nothing seemed right. With all the X-10 devices the phone had to pick up, you had to put in a security code and then a code to operate the device. Also, most X10 devices worked on existing phone lines so they did not answer the phone for 30 seconds. This made X10 impractical. I came across the ELK 930 and I knew I found what I needed. The ELK 930 detects the rise in voltage on a telephone line when a phone is called. Since the 930 is not a relay I needed a relay so I could trigger my door buzzer. So Elk came through for me again with the ELK 960, which is a timed relay.
Check out the PDF diagram for the overview of how it all
Here is a list of everything that is needed:
1) For the phone line I used a VOIP phone line by using a Linksys - Sipura SPA-1001 and an account with Teliax. This is about $50 up front and $6 a month service fee.
2) To detect the ringing of the telephone I used an ELK 930 purchased at www.bassburglaralarms.com for $30.
3) To activate my door buzzer I used an ELK 960. Purchased at www.bassburglaralarms.com for $18.
4) 1N4004 Diode. If you know what this does stop reading and do it yourself because I still have no idea. Purchased at Radio Shack for $.50.
5) A 12 volt DC power supply ó I used an older blackberry charger and cut the end off. Any 12-24 volt DC power supply will work.
6) A volt meter (not required but good to have).
7) Standard 2 wire phone cord. Purchased at Radio shack for $5.
Step 1) Cut one end off the phone cord and strip the two wires. Now connect the 2 wires to the T and R on the 930. I am 98% sure it doesnít matter which one goes where. I have the red on the R (ring) and the green on the T (tip).
Step 2) Run a wire from the negative on the 930 to the negative on the power supply. I spliced this wire onto the wire that was already attached to the power supply. If you do use an existing power supply and cut the end off like I did, make sure to use a volt meter to figure out which side is positive and which is negative.
Step 3) This step is probably the trickiest. You need to run a line from the negative on the 960 to the negative on the power supply but you need to put the diode inline. The diode has to be hooked up in the correct direction. The silver band on the diode should be on the side of the diode closest to the power supply. I hooked up one end of the diode to the two wires I spliced together in step 2 and connected the other end of the diode directly into the 960 (see picture). This probably isnít the best way but it worked for me.
Step 4) Hook the power supply positive output to the 960 positive terminal.
Step 5) Connect the out terminal of the 930 to the Trigger (TGR) terminal of the 960.
Step 6) Make sure all the jumpers on the 960 are set correctly. JP4 must be set to A and JP5 must be set to - (negative). JP2 must be set to 1 shot or the relay will continually trigger itself (I learned this one the hard way). JP3 should be set to begin. JP1 should be on SEC which means the dial ranges from 1 - 60 seconds. My dial seemed to be very sensitive. A very small movement could be 5 seconds.
Step 7) Go over your connection one last time then plug in the power supply. The relay should trip as soon as you plug it in and stayed tripped for whatever the timer is set to. If you unplug the power supply leave it unplugged for at least 5 seconds or the 960 doesnít trip the relay when plugged back in. Iím not sure if this matters though.
Step 8) Plug the other end of the phone cord you cut in step 1 into your phone jack. At this point you should have
everything connected and working except the connection to the door buzzer. I suggest testing now before hooking it up
to your door. If the relay is triggered you did everything right so far. If not, this is where you need the volt
If everything worked all you need to do is hook it up to your door opener. Mine was very simple. I opened it and it was obvious that all that happens when I pushed the door buzzer button was it closed a circuit. If you donít know what that means you probably didnít get this far. If you are not sure how to hook this up to your door buzzer I recommend you ask someone with some electrical background. I have a very limited electrical background and I figured it out without much trouble. If you have a newer model this might not be the case. I have no idea if the newer ones work the same but I would guess they do. If you have a problem hooking up the ELK devices I suggest calling ELK ó their tech people were great. Good luck. I would also suggest holding onto the 2 plastic containers the ELK 930 and 960 came in. I used one of them to hold this setup so it was nice and neat and my girlfriend wouldnít complain about wires everywhere.