SHOWALL FUN PRANKS HIGH VOLTAGE LAZARUS-64 PHOTOGRAPHY SPY GADGETS VIDEO GAME
Figure 2 - This is the schematic for the repeating camera timer project
Figure 2 - This is the schematic for the repeating camera timer project

Looking at the The Schematic shown in Figure 2, you can see that it also includes the two relays and driver transistors from a previous project called the "Camera Trigger Hack". The new components include the 555 timer oscillator and the 4017 digital decade counter, which will allow up to 10 digital devices to be actuated one after the other. The operation of this circuit is very simple as it is just a variable rate pulse timer driving the clock input on the decade counter. To give the camera some time to focus before shooting, the focus relay is set off by count 0 and the shoot relay is set off by count 5. The counter always counts from 0 to 9 and then repeats, so this spacing offers the most time between functions.

Transistors Q1 and Q2 are relay drivers, which are actuated by the digital signal coming from the currently active pin on the 4017 decade counter. Potentiometer VR1 allows the pulse rate to be controlled to a large extent, but the capacitor C1 is responsible for setting the overall range of time, which could be as fast as several pulses per second to only a few pulses per hour. A value of 1 uF for C1 will allow VR1 to set the rate from several shots per second and a value of 1000 uF for C1 will slow down the pulse rate to 10 minutes or longer. You will have to experiment with larger capacitor values if you want to really slow down your frame rate. A value of 10 uF is probably a good start.

Resistor R5 and the LED are optional, as it is just a "heartbeat" that will show you the rate of pulses coming from the timer. It is nice to have the LED installed during the testing phase as it gives some indication of the circuit operation. During my build, I also added LEDs to the control lines, so I had three LEDs in total.



Figure 3 - Breadboarding the circuit to test various capacitor values
Figure 3 - Breadboarding the circuit to test various capacitor values

The first capacitor I tested in the circuit shown breadboarded in Figure 3 was only 1 uF, so it gave a fairly quick pulse rate, allowing adjustment from about one photo per second to speeds that were too fast to control the camera. This rate was too fast to be much use, but made it easy to take videos of the circuit in action. My intention was to use this system to perform time lapse photography, so I ended up installing a large 470 uF capacitor after I was finished testing. You will have to experiment with various values for capacitor C1 to find the range you are looking for.

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