Photo Sensitive Clock Signal - Electronic Circuits Projects Diagrams Free

omega3387 · 12th September 2007, 07:10 PM

Well I will try to give you as much information as possible. Am am trying to build a circuit that will produce a clock signal for a counter. However this clock signal should be triggered by a change in light for a photo transistor or photo resistor. I have VTT7122 photo transistor and VT906 photo conductive cells available.

Per say:

A cup is resting on top of the photo transistor. When I lift the cup or object it will create a clock signal that will increment a counter by one. The table will be have plenty of ambient light to ensure that the photo transistor work properly.

Sorry I did not specify earlier, but i would like to make it using only IC's if possible. IF this is not possible what micros are good to work with that you have had good experience with.

Any help is greatly appreciated.

ecerfoglio · 12th September 2007, 07:44 PM

Your bigger problem will be to ensure that there will be only one count each time the cup is lifted.

Use a schmidt (spelling?) trigger between the phototransistor and the counter. Perhaps one gate from a CD 4093.

Also some low pass filtering (a small capacitor between the phototransistor's output and ground) will help.

Roff · 12th September 2007, 07:55 PM

If you use a microcontroller for your counter, software filtering could eliminate the multiple transition problem.

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12th September 2007, 07:10 PM	(permalink)
omega3387	Photo Sensitive Clock Signal Well I will try to give you as much information as possible. Am am trying to build a circuit that will produce a clock signal for a counter. However this clock signal should be triggered by a change in light for a photo transistor or photo resistor. I have VTT7122 photo transistor and VT906 photo conductive cells available. Per say: A cup is resting on top of the photo transistor. When I lift the cup or object it will create a clock signal that will increment a counter by one. The table will be have plenty of ambient light to ensure that the photo transistor work properly. Sorry I did not specify earlier, but i would like to make it using only IC's if possible. IF this is not possible what micros are good to work with that you have had good experience with. Any help is greatly appreciated. Last edited by omega3387; 13th September 2007 at 02:27 PM.

12th September 2007, 07:44 PM	(permalink)
ecerfoglio	Your bigger problem will be to ensure that there will be only one count each time the cup is lifted. Use a schmidt (spelling?) trigger between the phototransistor and the counter. Perhaps one gate from a CD 4093. Also some low pass filtering (a small capacitor between the phototransistor's output and ground) will help. __________________ E Cerfoglio Buenos Aires Argentina

12th September 2007, 07:55 PM	(permalink)
Roff	If you use a microcontroller for your counter, software filtering could eliminate the multiple transition problem. __________________ Ron (aka Rube)