stopwatch

vla7

I am building a lap timer for a radio control car track. It will basically consist of an IR emitter and receiver. Every time the car passes where the emitter and receiver line up it will block the signal therefore changing the state of the receiver. Is there a way to have the basic stamp keep track in seconds how long it takes the receiver to go from a 1 to 0 to a 1 again (therefore the car having completed one lap). I'm not concerned about precision more than I am concerned with consistency. In fact I could live with it being a few seconds off so long that it is consistent.

Thank You, any help would be greatly appreciated.

vla7

Qwaszx72

counter var word
counter = 0
do
pause 950
counter = counter + 1
loop until in0 = 1

debug "It took ", dec counter, " seconds for the Boe-Bot to complete one lap."

Mike Green

The problem with Qwaszx72's suggestion is that the Stamp will miss the car going through the sensor because the Stamp is waiting in the PAUSE for most of a second. That's the right idea though. Say that the car will block the sensor for at least 1/20th of a second. (There are ways to stretch that out if needed using a resistor and capacitor.)

seconds var word
ticks var byte
start:
seconds = 0
do
for ticks = 1 to 20   ' this loop should take about a second
if in0 = 0 then goto lap   ' check for car passing lap
pause 50  ' wait for 50ms
next
seconds = seconds + 1   ' we've finished one second
loop

lap:
debug "It took ",dec seconds," for the last lap",cr
goto start