How do I test if the SPG1 photogate is working without using a flash?
Connect a red LED from pin 7 of the 555 timer to the 9-volt row through a 470-Ω resistor. Note that the longer leg of the LED is positive. When the photogate is beam is unbroken, the LED should be lit. The LED goes out when something passes through the photogate. (This tip comes from Brian Rowe. Check out his splash photo here.) The newest versions of our kits (v10) incorporate this indicator LED. 8. I notice some variation in timing with an SPG trigger even without making any changes to the delay, sensitivity, or positions of the parts of my set up. How much variation in timing is to be expected? Martin Waugh did some testing of the 555 timer and found that with an average delay of 113.038 msec, the times varied from 112.821 to 113.687 (113.038 +0.65/-0.21) msec. That’s a little more than half a percent. By the way, check out Martin’s website, Liquid Sculpture. He takes phenomenal photos of splashes.
