Two IR detectors into one input

[holabr]

I have a Comcast digital adapter that came with a remote sensor that plugs into it (3 conductor 1/8" plug tip is +5 vdc, ring is signal, and collar is ground). I would like to be able to control the adapter from two locations. I tried to use a stereo Y splitter to connect 2 sensors into the single jack on the back of the unit, however when both sensors are plugged in, neither works. If I unplug one, the other works fine and visa versa. Any ideas how I can get both to work? I'm on a very limited budget, so buying other expensive equipment is not an option. Is there a simple circuit that would take the input from either sensor and pass it on to the adapter?

 

[nandhu015]

a simple OR gate will solve your problem

 

[holabr]

Can you expand a little with maybe a schematic? I'm a relative newbie.

 

[ard]

Hi, I'm kind of surprised that they dont work in parallel, as your typical 3pin IR modules usually have a weak pulled-up output and I've seen modules being used in parallel though not for the reason you intend to. The circuit I'd seen parallel'ed multiple modules, each meant for a different carrier so that the receiver could get a signal from a range of carriers.

Anyway, in your case, I think Nandu's suggestion can be implemented by simply using 2 signal diodes (1N4148 or any); connect the cathode of each to each of the IR module outputs; connect the anodes together, and pull them high thru' a 10K resistor; this becomes your OR'ed composite output.

Havent actually tried this, but should work.

Regards,

Anand Dhuru

 

[montech]

Ahhh steering diodes:wink:

 

[holabr]

I finally got the parts together and made the OR'ed composite circuit suggested above. Unfortunately it still doesn't work. When I plug the IR modules into the composite modified Y connector, the first one plugged in works and the second one doesn't no matter what combination I try. It's almost like there isn't enough power to power both modules. Any thoughts? Can I add an external power sorce somehow?

 

[CMOS]

a simple OR gate will solve your problem

Or gate will not work with remote sensors because the output of sensor is always pulled high when no signal is present. So when one sensor is receiving data, other sensor's output is still high which will keep the output of OR gate high.
He needs an AND gate for his application. Though this will work only if one sensor is receiving data at a time.
Better solution is to use IR repeater available ready to use for cheap or you can build one yourself like this one DIY IR Remote Control Repeater

 

[holabr]

Only one sensor at a time WILL be receiving data. How do I build a simple AND gate?

 

[CMOS]

Only one sensor at a time WILL be receiving data. How do I build a simple AND gate?

See attached schematic.

 

[holabr]

Since I don't have a 74hc08 on hand, I did a seach to see how to build one with descrete components. I found these two drawings which appear to be opposite of the circuit I built. My circuit looks like the AND gate drawing. Should it have been the OR gate as shown in the other drawing?

 

[CMOS]

The AND gate should work. Again note that there should be absolutely no interference from other sensor while one is receiving data and the cable length should not be very long.

 

[FvM]

Did you notice, that IR detectors usually have open collector outputs? Connecting both sensors in parallel should be the simple ans straightforward solution.

 

[CMOS]

Did you notice, that IR detectors usually have open collector outputs? Connecting both sensors in parallel should be the simple ans straightforward solution.

Not all of them are open collector. I have been using TSOP1738 and it has internal 80k pullup.

 

[holabr]

The first thing I tried was to plug the two IR detectors into a Y splitter then into the Comcast box. That did not work. Neither detector was detected when both were plugged in.

I then built the "OR'ed" circuit ard suggested in his post (which actually is the same as the "AND" circuit that CMOS suggested) and it only work for the first detector plugged in. Very strange. I'm confused.