Hi,
Brand new to arduino and have a couple of questions if someone would be willing to help. I need to make a motorized turntable. I need the turntable to do a couple of things and I would like to confirm that these can be acomplished with arduino.
-control speed of the motor
-change direction of the motor
-have the motor stop at evenly spaced intervals (be able to set the number of stops)
-have the arduino send a signal to a photo flash to fire when at each stop.
Also if these are all possible can anyone provide a basic overview of what will be required. Not detailed just an overview. Need a certain board, controller etc.
Probably the easiest way would be to use a stepper motor (probably geared down with a couple of toothed pulleys and a toothed belt so they don't slip). You would need a driver chip for the stepper motor and you would need an interface to the photo flash. There are two aspects of the flash interface - 1) the right connector to the flash and 2) making sure you handle the flash voltage correctly. Most (all?) of the newer flashes should be fine with the low voltage on the control terminals, but some of the older flashes (vivitar 285 if I remember correctly have something like 100 volts on them (there are two versions of that flash the 285 and the 285HV - the "HV" version is safe with the new cameras and their low voltage flash trigger circuits). The stepper motor would be controlled by the Arduino (there are stepper libraries) - you can tell it how many steps you want it to move then stop - that would give your turntable the rotation/stop feature you want. As for the flash trigger portion, I would use a opto-isolator, but you will have to do a bit of research on that - I have not built one of them, so I would also have to do the research. That should get you started. Start by finding a tutorial on "stepper motor basics" if you are not familiar with them.
There have been many Threads about photo turntables. Google should find them for you.
If you are using the turntable for still photography I doubt if there would be any need to gear down a stepepr motor. You can take as long as you like between steps.
If you are doing movie photography a stepper motor (even with gearing) might be too jerky and you might need a low geared DC motor with a rotary encoder to identify position.
Yeah, I was thinking of gearing it down simply to give better resolution. One thing that did come to mind just as I was falling asleep last night (when I do my best thinking I guess) was it also needs the provision to either automatically or manually set the "0" reference so he knows how to get to a particular spot in the rotation. I was thinking it was for still photography (changing views of an object using a macro lens for example), but, as you point out it may be video which has it's own set of issues including moving "smooth" during rotation.
Thank you for your help so far. This is for still photography however sometimes we shoot 24 frames per sec with the motordrive on Canon 5D markIII and just run the motor constant (client requirement).
There isn't much of an issue building the turntable it's mainly how to control it with Arduino. I'm thinking maybe use a dc motor from a treadmill and a motor breakout board with Arduino. I think I can fire the camera using a pocket wizard hooked to the Arduino.
All other suggestions are greatly appreciated and thank you again.
The problem with just driving it with a dc motor is fulfilling the last two of your requirements:
-have the motor stop at evenly spaced intervals (be able to set the number of stops) -have the arduino send a signal to a photo flash to fire when at each stop.
That would require some sort of position encoding so that it knows where it is - that was why I originally suggested a stepper motor since you can tell it you want to move 35 steps for example and that will be the same amount each time.
kaijorg:
Thank you for your help so far. This is for still photography however sometimes we shoot 24 frames per sec with the motordrive on Canon 5D markIII and just run the motor constant (client requirement).
You need to explain if there is a relationship between the 24 frames/sec and the movement of the turntable.
24 fps sounds like a movie.
"motordrive" makes me wonder if you are using an old-style film camera? How many frames are there on a film?