Control for camera rig no. 3

[Circuit] [Wiring]

This camera rig works automatically without a remote control system. During one complete turn the camera takes photos by mechanical push on a switch. A delay for the first photo is nescessary to have enough time to set the camera rig at the right height. The speed of turning the camera is extremly reduced to have enough time for the camera to shoot the photos.

Functional Description
The circuit diagram shows the circuits for delay timer for start, the timer to leave the stop position and the circuit to drive the motor with reduced speed. The wiring diagram shows the connector for the parts in the mechanic.

The delay timer starts with a negative edge for about 68 seconds. During this time the camera rig should reach stable the height. After the delay time a second timer (U1B in HEF4538) starts with a time of about 15 seconds. The output of this timer controls the driver for the motor. During the work of the second timer the mechanic have to leave the stop position. After that the switch controls the driver for the motor until the mechanic reaches the stop position again.

The motor is controlled by the timer circuit NE555 with pulse width modulation (PWM). The circuit drives the motor with pulse length of about 3.3ms. The time between the pulses is adjustable from 49ms to 374ms and controls the speed of the motor without reducing the force of the motor. The timer circuit provides a duty cycle from 0.06 (fast speed) to 0.008 (slow speed). The diodes D1 and D2 are a OR wiring to enable the motor control circuit. If the start timer works (MOT_EN=5V) or the mechanic is out of the stop position (SW_MOT1=5V) than the motor is turning.

In the wiring diagram you see how to connect the parts in the mechanic to the electronic circuit. With every push on the start switch S3 the sequence of delay time and start time is repeated. For the motor with a gear a modified servo for endless turning is useful. The stop switch S1 is normally closed. Reaching the stop position S1 switches the motor driver off. The voltage for the circuit should have 4V to 12V. So you can use small battery sizes for the power supply (9V block). The switch for shutter release of the camera (S2) is a seperate circuit with no contact to the electronic circuit.

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