Science Buddies: "Ask an Expert"

I am doing the project here https://www.sciencebuddies.org/science- ... #procedure

I have built the circuit following the instructions and when I put it in my dataq DI-145 and connected it to the computer, I am not getting a signal. It should be 5v when I shine the flashlight on the senor, but I'm getting nothing. When I touch the positive 'pin 2' to the resistor connected to 'pin 3' as the output, I get an output of 4.7 volts continually.

here of pictures of the circuit and how I connected it to the A/D convertor. What did I do wrong?

http://i.imgur.com/xP5HmCY.jpg - I put 3 AA batteries in the connected battery holder as well.

http://i.imgur.com/sNCkZtC.jpg - this one is a little blurry. the resistor output is curved around from 'pin 3' to the + input on Ch1 on the A/D convertor, and the end of 'pin 1' is in the -(negative) input.

I'm hoping that I misunderstood the construction of the circuit and someone can tell me how to fix it. Otherwise, I'll have to do a different science project and will have wasted $40

Hi Logan -
From what I see in your 2nd picture, the resister is soldered to the correct pin on the IC but the other end is just floating. It needs to be connected to ground so that a voltage is developed across the resister. Let me know if it works once you have connected the floating end of the resister to ground.

All the best,
Gerry

After you said that and I went back and looked at the directions, I realized that's what I was supposed to do. I soldered the resistor from pin 3 to pin 1(ground). I went to hook it up and once again, there is no output (except the 5 volts when I touch 3 to 2, but this is unaffected by the light sensor.)

Any other reason it wouldn't work?

I'm on a very limited time schedule at this point, so a quick reply from anyone would be very appreciated

edit: if it means anything, when I remove 1 AA battery, I get no output when I touch 3 to 2, instead of what I expected - 3v, down from 4.5-5

Bump? = )