Hey everyone, I'm very much so a newbie at electronics, but figured I'd try and tackle a problem for my scout group: making a pinewood car timer.
I found this schematic online that uses optical transmitters:
I have hooked everything up as seen in the schematic to the best of my abil ity... I have hooked up the parallel port grounds (Pins 18-25) also to the negative row at the bottom of my breadboard, so all the grounds are on the same line (I couldn't figure out how else to do that).
Here's my problem: Using parmon to monitor the parallel port, when I hit a ny of the sensors (say the start gate for example), it changes the status o n all the pins that are hooked up.
Example: Pins 10,11,12,13, and 15 all read "1". I trigger the start gate switch (ho oked up to pin 15). Now ALL of my pins (10,11,12,13, and 15) all toggle ov er to "0". Similar thing happens if I hit just ONE photoelectric diode wit h a flashlight, ALL trip to 0, not just the one pin that that diode is hook ed to.
I've written my matlab code to poll everything and run the race, but since I can't differentiate which sensor is getting twigged, I can't determine wh ich sensor came across first...
Any help/suggestions would be fantastic.
Thanks in advance, Andrew