This project is aimed at converting a pair of old Broadcast Camera, remote controlled Pan and Tilt turrets into useful modular mounts. The turrets will be able to take a selection of equipment, though mountings for a DSLR camera are the main goal, as well as control.
The turrets were originally used for broadcast TV cameras. They are relatively large, but neat in design. The shell is fiberglass and most/all of the joints appear to still be water resistant. It was originally designed for use on helicopters or boat and so needed to be weatherproof and robust.
The tilt is fitted with a harmonic motor, with DC drive and an analog voltage output showing speed. It also has a potentiometer for measuring absolute position. The tilt motor seems to operate well at 6V, though it could likely go higher. It also has a pair of limit switches.
The Pan is also fitted with a harmonic drive motor, with tacho output. This seems happy and fast at 12V and a couple of amps. A quadrature digital position encoder fitted to the base and a couple of limit switches are in place here as well.
The plan is to place most of the electronics in the base of the turret. An arduino will be used initially, with thought given to adding a Raspberry Pi later.
There is a route to run cables out the bottom of the unit, though it is a pain to do. The current plan is to run 1x Serial Data, 2x Cat 6, 2xUSB, 1x Regulated 12V and 1x Unregulated power (13-36V DC for batterys etc). This gives plenty of options for getting data in and out.
Pin wise for the Arduino, everything other than the motors seems happy at 5V, allowing for direct connection. It might be worth buffering some of them in the final design. The motors will be driven off of 12V via a motor shield, the tilt will be limited down to 50% duty in software.
|Function||Pin||Direction||Wire Colour||Max Volts||Signal Type|
|Pan Motor +ve||???||Output||Red||±12V (PWM)||Drive +ve for clockwise, -ve for anticlockwise rotation.|
|Pan Motor -ve||???||Output||Black||OV||Motor Ground Reference.|
|Pan Tacho +ve||???||Input||Red/White||±5V||Speed and direction in analog form, will need some rescaling.|
|Pan Tacho -ve||???||Input||Black/White||OV||Tacho Ground Reference.|
|Pan Encoder +ve||???||Output||Red||5V||Power for encoder circuit.|
|Pan Encoder -ve||???||Output||Black||OV||Ground reference for encoder.|
|Pan Encoder reference||???||Input||Green?||5V||Reference pulse from encoder.|
|Pan Encoder Output A||???||Input||Blue?||5V||Pulsed output from encoder.|
|Pan Encoder Output B||???||Input||Yellow?||5V||Pulsed output from encoder.|
|Pan +ve Limit Switch||???||Make/Break?||???||5V||Positive limit switch (will need some circuitry)|
|Pan -ve Limit Switch||???||Make/Break?||???||5V||Negative limit switch (will need some circuitry)|
|Tilt Motor +ve||???||Output||Red||±12V (PWM)||Drive +ve for clockwise, -ve for anticlockwise rotation.|
|Tilt Motor -ve||???||Output||Black||OV||Motor Ground Reference.|
|Tilt Potentiometer +ve||???||Output||???||5V||Potentiometer Power|
|Tilt Potentiometer -ve||???||Output||???||0V||Potentiometer Gound|
|Tilt Potentiometer signal||???||Input||???||5V||Potentiometer Output|
|Tilt +ve Limit Switch||???||Make/Break?||???||5V||Positive limit switch (will need some circuitry)|
|Tilt -ve Limit Switch||???||Make/Break?||???||5V||Negative limit switch (will need some circuitry)|
From previous experience with Pan&Tilt cameras, the best control system is a packet based system. It should work with both 2 way and 1 way communication. The primary method should be incremental not absolute position, with absolute available. It should also have speed control as an alternative. It should periodically report it's current state, with faster reporting when updating. It should also have the ability to carry extra data to pass on to the camera, or whatever is mounted in the case. A calibrate function would also be useful.
|Header||Checksum||Inverse Checksum||Packet Type||DATA||Footer|
Moves to limit switches to confirm true position.
|Pan Speed||Tilt Speed||Zoom Position||Focus Position||Iris Position|
|Pan Position||Tilt Position||Zoom Position||Focus Position||Iris Position|
Other Data packets
Type 0x03 Data passed directly on to next link
|Data Byte Count||Data 1||Data 2||...||Data N|
|Pan Position||Tilt Position||Pan Speed||Tilt Speed||Zoom Position||Focus Position||Iris Position|