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Registered Member #2140
Joined: Tue May 26 2009, 09:16PM
Location:
Posts: 53
So i got a counter today, and i wanted to make basically a stopwatch as a chrono graph. It works at 10kHz, so it is plenty accurate. I am trying to think of a way of basically activate an IGBT when a photogate is triggered, keep it on, and turn it off when the second photogate is activated.
When the photogate is activated, a voltage is given out, very briefly (while it is blocked). Is there a way i can go about this using only 555's (all i have now)?
Registered Member #2040
Joined: Fri Mar 20 2009, 10:13PM
Location: Fairfax VA
Posts: 180
You can set the 555 up as a monostable timer, connect the photo sensor signal to the trigger pin of the 555, and then connect the second photo sensor to the reset pin on the 555. As long as the timing cycle is longer than the time it takes your projectile to move from the first sensor to the second you are set, you can use an arbitrarily large value since you wont actually be letting the timer reset on it's own.
a D-type flip flop would do the job too, and will probably be easier. Just pull D high, then connect the first sensor to the clock, and the second sensor to reset.
Registered Member #2040
Joined: Fri Mar 20 2009, 10:13PM
Location: Fairfax VA
Posts: 180
Or a toggle flip-flop with a diode OR gate at the input (if required). Although the 555 has the advantage of "timing out" in case of a triggering error with the second photo sensor.
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555 "Stopwatch"
