Submitted by psychoanalyst_god on Sat, 07/10/2010 - 18:29
Posted in
Hello All,
I am very new to the world of DIY motion control. I am reading a lot everyday to make up for my lack of training and knowledge in this field (I am a Chemical Engineer/Materials Scientist) and its been a very exciting few days.
My question relates to macro photography and a custom setup I am trying to build for that. I have a lot of macro gear including a Nikon PB-4 bellows unit, and lenses that can take me all the way from 1:2 to 5:1, leading to obvious depth of field problems, for which I am considering stacking my shots. I shoot with a Nikon D200 btw..
This is something that I can do it by hand, but I thought it would be more fun if I can build my own little setup.
One of the goals is to control the PB-4 with a stepper motor using Arduino. My initial thought is to couple the stepper motor with the bellows movement knobs on the sides and use that to rotate and control the linear motion of the bellows.
I was looking for recommendations for motors I can use, because I have no idea what the torque requirements would be. I don't except to use heavy lenses with the bellows.
Also....can the Arduino board power the motor, or do I need to get a separate power supply? I intend to use the setup in the field, so the Arduino itself would be battery powered.
I would appreciate any information. I apologize before hand, if the questions are very elementary, but I am somewhat of a noob in this field.
Thanks and regards.
Hi, I'd say use an
Hi,
I'd say use an easydriver with a stepper like the ones you get from sparkfun, get a toothed belt and two toothed gears (1:6 ratio or better), an arduino and the OM engine and you are all set. The Sparkfun motor I have draws max. 500 mA, so any decent battery (like a car battery) should be able to power it for hours...
If you set the easydriver to 1/16th microstep and the gear ratio at about 1:6 (thats what I have on my dolly), it should work pretty good, even for macro.
Matthias
Matthias, That really helps.
Matthias,
That really helps. I think I can get the 12V stepper from a friend.
One confusion.....would I need a separate stepper board (I am guessing the easydriver is a stepper board?) AND an arduino?
So, in effect the Arduino drives the stepper board?
Whats the best place to buy the gears and belts?
Regards.
Yes, you do need both, an
Yes, you do need both, an arduino and the stepper driver. The arduino supplies step and direction signals to the driver.
I got my gears and belts from RS Components in Germany, but I bet there are other sources in the US. Maybe we should prepare a list of suppliers in a dedicated forum thread ?
If you're in the US, a good
If you're in the US, a good supplier for gears and belts is Stock Drive Products / Sterling Instruments. It's where I buy the vast majority of my stuff -- the URL is http://sdp-si.com/eStore
But yes, the Arduino connects to the stepper driver, and the Arduino runs the firmware that lets you control the stepper and camera.
One of the things I recommend generally though, is to get a stepper with a badge rating of no more than 1/2 the voltage that you're going to run at (6V badge rating for 12V supply), so that you can effectively take advantage of the chopping capabilities of most stepper drivers. It's not essential, but it will result in higher torque at higher speeds.
!c
As far as mounting goes, you
As far as mounting goes, you need to pick the stepper motor you want, and then I'm betting you can pull off that knob on the PB4, then measure the diameter of the shaft it's attached to.
Then, drop by somewhere like dumpstercnc.com and pick the right coupler to couple the shaft of the motor to the shaft of the PB4. Then, make a simple plate to mount the motor to the bellows in some fashion, and use the coupler to attach the motor shaft to the bellows shaft, and that should be the bulk of your mechanical work.
As for torque, that's not as simple for us to help you with remotely. You'd need to know the torque to operate the bellows knob - not the weight of the camera + bellows. You can measure torque similar to what's done here: http://www.scienceprog.com/easy-way-to-measure-motor-torque/ -- in this way, you could determine the minimum torque required to rotate the knob, and then multiply by 2 or 3 for safety.
Edit: forgot to mention about gearing -- you could use a pulley reduction and skip the coupler by finding a pulley that will mount to the adjustment shaft of the bellows.
!c
Matt and Shutrerdrone, you
Matt and Shutrerdrone,
you have been most helpful.
I am going to start working on this, this weekend. I first need to arm myself with an Arduino and the Stepper+Easydriver.
To confirm: I would need 2 power supplies? One for the Arduino and one for the Motor?
Regards.
If you run the motor from
If you run the motor from 9-12V, you can use the same power supply. Just make sure the power supply is capable of supplying enough current for both.
!c