I recently got my hands on a medium duty pan/tilt head designed for an outdoor security camera, and I want to try and turn it into a hot head that I can mount on a jib arm. I know it works, though I haven't yet tested it myself.

I have the head ONLY, so there's no power or control cables with it. I'm trying to figure out how best to make a pan/tilt control unit that will give me variable speeds as opposed to a fixed "push button" control. I have yet to figure out if the control is logic based or if it's a simple "circuit on, circuit off" method.

The company that makes the head no longer exists, so I've had a lot of trouble finding documentation.
Here's what I know about the head:
Make/Model: Javelin Systems/ JPT35
Power: 24V AC, 8 volt amps
Power Connection: Amphenol 4 pin male recepticle
Control Connection: Amphenol 7 pin male recepticle
Weight: about 25lbs
Payload: 30kg? (I compared this head to others with similar specs and that's what most of them can hold)

Anyone have any ideas? Anyone done something like this before? I'll try to post some pictures of the head when I can.
Thanks!

If I remember correctly the changing of speeds is done by either
changing the voltage to the motor (linear motor?) or changing
the frequency of the pulses (step motor?). Make sure you do not
give it more voltage than it can take.

Hi Matt,

You're going to need a speed controller. Not cheap. Some controllers will control two motors. Others, just one. So if you get the kind that controls one motor, you'll need two: one for the pan motor and one for the tilt motor. Having said all that, I have no idea how you'd connect it into your remote head, or if it would even work. Also, security pan/tilts can be too noisy for dialogue scenes. Something to keep in mind before you spend the cash fixing this thing up!

Dan
www.DVcameraRigs.com

Rob wrote:

If I remember correctly the changing of speeds is done by either
changing the voltage to the motor (linear motor?) or changing
the frequency of the pulses (step motor?).

In many cases you can regulate DC voltage (and thus the speed of the motor) with pulse width modulation (PWM). For example, see this article on building a pulse-width modulator (http://www.solorb.com/elect/solarcirc/pwm1/).

According to the article, PWM is good because "the pulses reach peak supply voltage and will produce more torque.." but can generate RFI (which the article tells you how to fix).

Stepper motors work by sequentially pulsing different coils around the motor. (This circuit for controlling a stepper motor (http://www.aaroncake.net/circuits/stepper.htm) works with just two coil sets.) If a single step of the motor produces visible movement, it's not suitable for general camera control. You may have to do a lot of physical speed translation (gears or pulleys) and some damping of the jerks to make a stepper motor smooth enough for movie work.

Read this article about stepper motors (http://www.cs.uiowa.edu/~jones/step/) for more about stepper motors.

Michael

Wow, great info guys. Thanks!

I've opened up the head (that thing is ironclad!), and I can't tell whether the motors are stepper or linear. I'll have to do some more research on the make and model of the motors. There are two motors, so more $ in the speed controller dept? I'd like to DIY as much as I can, but if it ends up not working at all... Hey! It was free to begin with.

Also, the head is 24 volts *AC* not DC, in case that makes any difference.
I'll post any updates on this project in case anyone is interested.

Thanks again for the help!