measuring time intervals

[stameni]

I want to make a time-counter, which measures times between two events (event is just an interrupting of a light beam). I’ve been thinking to use double source of light and the appropriate detectors, once for initiating measuring and the other one for stopping. I thought the easiest way was to use laser diode within the visual spectrum (for more precisely pointing its light to the detector). Detector would have a response time of approx. 500-700 microseconds, AND output within the TTL limits, so that it just could be connected directly to a microcontroller.

If this was possible at all, I’d like to know which parts to use, how to drive laser diode and detector. Did someone do that before?

Thanks,
Ivan

 

[MacGyverS2000]

If you're already connecting this to a microcontroller, which is the lion's share of the work, what else do you really need to know?

If this is a one-off, I'd pick up a cheapy Radio Shack laser pointer for a couple of bucks... those things last for a few hours easily between battery changes. All except the slowest of sensors (like maybe CdS cells) is going to be fast enough for 0.5ms response time... most fiber optic IR detectors work in the multi-kHz range without even thinking twice.

Google will come back with all kinds of light detector circuits...


Dan
Owner

http://www.Hi-TecDesigns.com

 

[IRstuff]

While going that route might be amusing, it does not appear that you have sufficient background to do it right. A photo interrupt switch is designed for this purpose. All you need to do is to mechanically arrange an opaque flag to interrupt the beam. The light source and detector are already designed for the correct signals, etc.:

http://www.americanlinear.com/html/vendor_links.html

as a example.



TTFN

 

[cbarn24050]

You don't need a laser, in fact the job is much harder with one, just a led with a lens at one end and a photo diode and lens at the other. Excite the led with AC, 1KHz for example, an op amp with suitable filter components on the photo diode (look up active filters) and your in business. Easy to get 50 feet, with care 200 feet is possible.

 

[stameni]

IRstuff:

What is the best photo interrupt switch manufacturer / model you can suggest?

Unfortunately, googling for "photo interrupt switch" returns only one hit.

You're right I have not enough knowledge; I'm rather a (uProc) programmer without much practical knowledge concerning the rest of the hardware.

Thank you all,
Ivan

 

[IRstuff]

try these for additional search ideas:

http://www.components.omron.com/Products-PM-NonAmpTrans.shtm

http://proximity-sensors.globalspec.com/Industrial-Directory/opto_interrupter_switch

http://www.allelectronics.com/cgi-bin/category.cgi?category=435&item=OSU-50&type=store

http://proximity-sensors.globalspec...ximity_presence_sensing/photoelectric_sensors

TTFN