Electronics > Projects, Designs, and Technical Stuff
DIY shutter speed meter made of logic chips
plazma:
I needed to verify the shutter speed of a CMOS camera. I ended up making a quick'n'dirty circuit of D-type flip flops.
There are 30 SMD leds in a row. One illuminated led is stepped every clock pulse. The led low side is controlled with an N-fet which is also connected to the clock signal. One led is on when the clock is high. This way the led duty cycle & brightness can be controlled by adjusting the clock duty cycle.
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If the clock is 1kHz the led is stepped every 1ms. With a 10ms integration time there are 10 leds illuminated in the picture.
David Hess:
Why didn't you use decoder/demultiplexers like the 74138 and binary counters? One 7493 and two 74138s (or one 74154) could drive 16 LEDs by themselves with very little wiring.
plazma:
There are many ways to do a stepping led circuit with logic chips. I had D-type flip flop chips in my garage from other projects. It was easy to cascade them as many as wanted. I used 30 leds since that's how many fits to the protoboard in one line.
First chip in the cascade is 74HCT74 since it got the set-direct pin (preset).
Caliaxy:
Cool! Obviously, you don’t own an analog oscilloscope :)
plazma:
--- Quote from: Caliaxy on February 06, 2020, 09:52:41 pm ---Cool! Obviously, you don’t own an analog oscilloscope :)
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Only DSOs in use. An analog scope would give much cooler pictures for the report :)
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