# Photo-gate Circuit HELP

Discussion in 'The Projects Forum' started by JoshAZ, May 26, 2010.

1. ### JoshAZ Thread Starter New Member

May 26, 2010
3
0
I am looking to make a photo gate circuit that allows an object to move a certain distance along a driving system, then stop by disengaging the driving force or turning it off.

Possibly Using a "ruler" system to judge the distance the object has traveled.

Example: Say I want an object to travel 3 feet then stop.
The idea would state that a photo-gate would measure the stance by a ruler through the gate and stop when it reaches that distance.
RULER (shown below)
0.........1'.........2'.........3'..........4'
█ █ █ █ █ █ █ █ █ █ █ █ █ █ █ █ █ █ █ █

Any Ideas on how this could be done?

I found a similar circuit online at the address below, but it seems to only have an on off switch for light/no light. This seems the simplest way of doing it because it would require no programming, but it I would rather the object slow down and speed up based on distance then this circuit is no good for my application.

http://www.hiviz.com/tools/triggers/triggers3.htm

Any insight and discussion is welcomed. My circuit knowledge is minimal (I have had 2 classes at the university level)

Thanks.

Last edited: May 26, 2010

Apr 20, 2004
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3. ### JoshAZ Thread Starter New Member

May 26, 2010
3
0
This is a good idea that I have not thought of, so thanks; However, I am trying to stay away from having to write a program for the circuit, do you think that would be possible with this kind of setup?

4. ### SgtWookie Expert

Jul 17, 2007
22,182
1,728
Sure; use a counter to count the tics on the scale.

Decrease the motor current as you see fit, depending upon the value left in the counter.

However, you could solve this so much more easily using a microcontroller that it isn't funny.

Learn microcontrollers, or be left out in the cold. Yes, there is a steep learning curve the first month or two. It gets a lot easier afterwards, and then you start to wonder how you ever got along without them.

5. ### JoshAZ Thread Starter New Member

May 26, 2010
3
0
Thanks a lot for the input. Do you know a site that has the basics of Micro-controllers? Until I can get a book on it and start to narrow that curve?