Hi,
Consider that in one case I have a wide angle lens and someone is walking close to the camera. A 90 degree pan might take 5 seconds.
Consider in another case I have a 150mm(35mm equiv) telephoto and want to slowly pan the horizon. That same 90 degree movement might take 1 minute. It needs to be very slow. Slower than the current geared motor can provide.
Slower is easy... Gear reduction and/or PWM control.
The range is not really all that large 5..60s is just 1:12 - very easy with PWM control, so just select the reduction to fit the max. speed and let PWM handle the 100% down to 8.3% range.
The solution is to use a slower motor, but then the upper range is now too slow. The motor I have now is satisfactory for the high speed work. It is not satisfactory for the slower pans. I could use two motors, but that is of course, not ideal.
If you wanted a purely mechanical solution (like 2 motors) you could just as well make it with an arrangement of small pulleys in the fashion done on a drill press with 2 or more sets of pulleys (or a fine pitch timing belt with suitable toothed wheels.
My experience with professional broadcast camera zoom lenses tells me the range I want and the control I want should be possible.
My experience with BC cams (which don't need the pro in front, as all BC equipment is pro by the very nature
) tells me that if you want that quality, you need a huge wallet. Thinking you can make a kitchen sink equivalent is very-very optimistic, unless you are a savvy engineer, knows the subject in your sleep and have a very well equipped workshop.
So, how are your skills in mech. engineering and how well equipped are you with power tools (like lathes, mills and routers)?
Indeed, but I thought that is what I was getting with the Pololu motor controller. Do you have any recommendations?
I take pride in constructing most of what I need, to get covered on the parameters I need, rather than buy ready made, so I cannot recommend you to buy product X over product Y, as I have no experience with neither of them.
I can however tell you how to make such stuff, if you are into electrical (and mechanical) engineering and have a well equipped workshop.
How did you set up your tests?
They need to be with a full load, so use some bricks or whatever (to spare your cam), and run some tests where you add two well planed circular plates of say 100mm (4") in diameter and assemble them with a high viscocity silicone grease as a brake - BC tripod heads use this method to help steadying the pan (and tilt) when used by a (human) cam operator.
Have you downloaded the data sheet for the controller?
And did you exhaust the possibilities in the controller set-up software?
It seems to have plenty of options... On the "motor" tab, you can set tyhe max. acceleration (and that might be just the ticket) and on the PID tab, you can play around with the parameters for P, I and D (Proportional, Integral and Differential gain) parameters.
Note the initial values and don't change more than one parameter in any one go (even if you are well versed in control engineering).
Try this first and if that won't do it, a combination of mechanical and electronic solutions can be tried.
You might wanna gear the motor down to the max. speed before playing with the controller software, as that will make it stronger (and the "grease plates" will cure lots of vibration/unevenness, so won't be a bad idea either).
You are controlling it with R/C protocol pulses, right?
