At school in physics we use optical gates and an electronic counter for e.g. measuring how long time an object uses to pass a given point etc. The optical gates are connected to electronic counters which measure time from the first time the beam is broken to the second time the beam is broken. Now, I would like to build one of these myself. I am assuming that I can just use a stopwatch for measuring the time (when you press the momentary switch once, the timing starts, and when you press it again, the timing stops). So what I need is an optical gate that can "depress" a switch. Am I right assuming that I can use an LED and one of those phototransistors that are found inn ball mice? How far away from the transistor could I place the LED? I would like at least five cm. And which color LED should I use? So what I need is a schematic for a device that depresses a button (connects two points) when a light beam is broken.
Um, I don't think you find photo transistors in ball mice. If I were you I would try and get your hands on any kind of equipment that you can find and experiment with it. Even though I haven't done any electronics for years I would try with a bright LED and an LDR of some kind. That might work in a darkened room anyway. You could try to get rid of outside light by putting the light sensor and led in black tubes so light can only enter/exit in one direction. Oh, also the stop watches we had at school had little sockets at the back which would allow you stop/start the stopwatch by connecting the terminals. You could integrate something like that directly into your light gate.
Ok, so maybe they're not photo transistors, but they are IR transistors. So I could make something like that I talked about, using one of these transistors and an IR LED right? I remember ZapWizard talked about the IR transistors from a mouse being able to connect to an other transistor... ZapWiz, you could probably help me out here
Hi mate, Im trying to make something similar but aint got it working yet. I can kind of go though what I have so far if you want, and you may be able to get it working, Im on MSN at Rascal1001@Hotmail.com
