Using a garage door Safe T Beam to trigger a prop

[dflowers]

OK,

here is my first question. I would like to know how I could use the Safe T Beam garage door safety beam to trigger a prop. It seems as though it would be fairly easy, but so far I have been unable to put  my mind around how they work. I know they both receive power and then transmit an infrared beam. Thats all I know, any ideas? Has anyone actually done this? Anyone know of an easier way to create an infrared "trip line." I know you can use devices like a motion sensor, but this looks like it would be great for a trigger for a walking path etc.

Thanks,

Dorian

[menehune]

I don't think it would be very practical or easy.  Do you have two wire or three wire sensors?  My garage door has two wire units and both units require power from the garage door drive unit.
I have not tested the units yet to see how the sensor sends back the "blocked" signal to the motor.

It may be easier to build a lightbeam unit of your own.  With a focused light source you could use a cds cell as a detector.

[JonnyMac]

Do you have the specs/tech data for the device you want to use?  We assisted many customers with various sensors, but we need the details to do it.

I have used a Parallax Ping))) sensor as an invisible beam break.  It's limited to about 10 feet and you need target to bounce the beam off of, but it works quite well -- and it plugs right in to one of our prop controllers.

[dflowers]

I have tried finding the specs online, but I have not been able to. Maybe I will buy a set and see if there is and spec info in the package. Thanks for the quick reply.

Dorian

[JonnyMac]

You need to determine the kind of output: it could be dry contact (like a relay) or it could be solid-state (like a transistor).  If it only has two outputs terminals then you need to know if it's normally-open or normally-closed (relay type) or open-collector or open-emitter (transistor type). 

The deity is always in the details....  ;)

[dflowers]

Ok, I know this is old, but now that halloween is over, this is what I have determined. There is a sending and a receiving box on either side of the garage door. Each box has a white wire and a red wire going to the two terminals on either box. When the beam is not broken, the voltage reads 11.28 VDC and when it is broken, the voltage reads 12.50 VDC. The voltages are the same if the garage door is opening or stationary. The wires leading from the boxes on either side of the door meet back at the garage door motor. There, the two red wires are attached to the same terminal and the two white wires are attached to the same terminal marked "common." So, what I am gathering from this is that some how the controller board in the garage door opener is sensing the raise in voltage caused by the beam being broken. Is there a way to duplicate this and use it for triggering a Prop-1 or Prop-2 controller? I am not sure how one would go about measuring the voltage change so that a Prop-2 could be triggered.

I also checked the voltage at the garage door opener and it is providing 11.28 VDC with the door stationary or moving, but if the beam is broken, it reads 12.50 VDC. So from this, the only thing I can figure is that the safety beam is being fed 11.28 VDC, but so how, when the beam is broken, the voltage spikes to 12.50 VDC and the system then senses this spike and raises the door.


Any ideas or further test that I should try in order to figure this out?

Thanks,

Dorian

[JonnyMac]

What would be best is to get the docs from the manufacturer.  The voltage change you're seeing could be due to a load change through thin wire.

[dflowers]

I just got off the phone with the manufacturer as well as a local distributer/installer and evidentally, they are very protective over this information. Even after telling them I wanted to use just the beam receiver and transmitter to trigger a halloween prop, they said it could not be done because the system was tied into the controller board for the opener. They said i was better off looking into something else. Now I feel even more challenged to figure this out. I will let you know if I figure anything else out with these.

[JonnyMac]

Give me as much information as you can (make, model, etc.) and I'll do what I can to help.  There may be some current sensing involved -- something typical in alarm systems as this prevents the bad-guys from simply putting a bypass across a sensor.

[menehune]

I wondered about that myself.  I have a garage door with one of those units.  I assumed it was a DC voltage from the motor and the sensor returned a AC waveform.  Never put a scope on the lines to check though...

[dflowers]

Jon,

Thanks for your help, I am still trying to do some research on my end also. I have not been able to find an actual model number on the beam transmitter and receiver themselves, however, the door opener is an Overhead Legacy Model 696 CD/B.

[dflowers]

Jon,

Would it be of any use if I disconnected the beam transmitter and receiver from the garage opener and connect them to a seperate power source and then see what happens if I break the beam? Just a thought, the voltage drop may be happening when the beam is intact and then returning to 12 VDC when it is broken. Just a thought.

[JonnyMac]

Can you take and post pictures of the thing? 

[dflowers]

Yes, I will try to get them up tonight or tomorrow.

[drewificus]

I have a pair of these (Model: GSTB-R  PN: 37334R) And it is clear that the sensor is a 2-40mA type device.  You can get a nice .5V - 3V signal across a 330ohm resistor using a supply voltage of 9VDC or 6VAC when you place it in series with the sensor.