IR Repeater Problems

I purchased an IR Sensor Module from Radio Shack to use for this IR Repeater project I am working on and I almost have it working but for some reason the data pin on the IR Sensor always has a 1.97v through it. It is well grounded and has 5v going to the Vcc pin. Any ideas why this analog sensor would have constant power through the data pin. (I know its not daylight interference either).

Make sure you have identified the leads correctly. How are you measuring the voltage meter or oscilloscope, if it is a meter and there is a pulsed signal on it it will not read correctly.

Can you point us to a data sheet for the sensor, it is almost impossible to answer the question without.

I have been unable to locate a data sheet for this sensor but the package had some info including the pinout so I scanned it for you to see.

http://www.dirtdon.com/IRPackage.jpg

I thought it might be import for you to see the schematics of what im building so I am including those as well.

http://www.cedarnet.org/smartware/Hardware/IR_Repeater/IR_RepeaterBIG.gif

I have found out that the power Im reading with my multimeter from the data pin on the IR sensor is coming from either the transistor or the 4 pin on the 555ic. Any Ideas why power would be feeding back to the data input?

Ok that gives me much more to go on.

As a test disconnect the 10K from the sensor and connect it to +5 and then to 0V and see if this turns the LED on and OFF. If you look at the LED through the view finder of a digital camera you can see the IR diode.

Now assuming that works, measure the output of the sensor with your meter (still having the 10K disconnected from the sensor but connected to 0V so the IR LED is on ). Does this detect IR light from the LED? That is does the voltage output change from 5V to 0V?

When it is connected up normally you will need another source of IR to trigger it but you can do those tests with it's own LED.

Ok so first, let me thank you for taking the time to troubleshoot with me.

So I disconnected the sensor and connected it to both 5v and 0v and the led turned on and off perfectly.

With the sensor still disconnected I used my meter and took a reading with no IR light and it was at 0v and then took another reading with it's IR Led held in front of the sensor and got a reading of 2.5v.

As I thought about it... shouldn't the sensor run high and drop in signal as it detects IR light? I thought thats what the transistor compensated for so that the input to the 555 was High at 5v...

First of all well done in getting so far.

shouldn’t the sensor run high and drop in signal as it detects IR light?

Yes that is what the circuit you are building expects. It looks like you have a light sensor that gives the inverse of the signal the signal of the original sensor.

So it looks like you might have to either change the sensor or add an extra transistor stage to get it the right way up. The extra stage would simply be 10K into the base, emitted to ground, 10K to + and collector and the collector to the base of the original transistor (no need for the 10K base resistor current is limited by the collector resistor).

Well thank you again for your response and I apologize for my delay but I spent the weekend troubleshooting this project and I am happy to report that I finally have a working IR Repeater!!!!! I found that the problem was my crappy RC IR sensor. It gave me very inconsistent readings and only had a range of 4 ft :( . So ripped another one out of an old DVD player and wired it up. Now the range seems limitless lol. Also I was on the wrong frequency. I broke down and bought a multimeter that reads frequencies so that helped out a lot. I used the original Schematic I posted with this senor, and only had to change the resistor values between pins 6 and 7 to get the right frequency. I ended using a variable resistor preset to get me to just the right frequency. But I can't thank you enough for your input, help and wisdom!

Thanks again, Don.