Hello all, I'm looking to make a rig/rail for my Canon 7d so I can move it in very fine incriments for high magnification macro photography (currently just one axis but eventually 3)
Once I have the code for driving the coils is it as simple as increasing the current ability of the arduino output by using a series of transistors, I have a bunch of IRF730 Mosfets that I was planing on using.
Sorry if this post seams a bit vague, please aask me if you need more info to answer my questions.
Hi milutiche,
I'll pop a comment while we wait for proper input.
If I get your setup right, then there is a mismatch between the mosfets and the steppers you need (a quick look at the specs: the mosfets handles up to 400 V and a handful of Amps).
The movement of the camera .. that's an external one, right? I mean, it moves the whole camera and not say turn the lenses? I think of the latter as a possible proper action to take to accomplish the job of 'fine-tuning a macro photography". Anyway, both cases takes much less power-input than the mosfets handles.
To handle the movement you may choose to turn the angular turn-around of the motor-shaft into a linear back & forth movement. A stepperangle of 200 steps pr turn is not out of the ordinary .. if the stepper drives a 'screw'-like axis, this setup is a 'gearing' of 1:200. That reduces the need for powering the stepper (on the expense of reducing a rapid linear movement) - and is in itself a very fine movement (1mm/200 a step if say the axis has a rise of 1 mm pr turn.)
Building a driver for a stepper is good sport, but they've dropped in price .. as a good sport newbie myself, I /did/ choose to buy ;o/
[edit: atleast consider starting out from a dual H-bridge]
I'm just starting up, playing with the servo that came with my kit, but I've already run into a common problem with Arduino's and motors, namely you generally can't have the motor use the same power line as the Arduino, since the motor will draw more amps and maybe run at a higher voltage than the Arduino can handle. Thus you need to plan for having a split power system, where the Arduino gets one supply, the motor(s) get another, and you connect the grounds together. There are several motor shields that sit on top of the UNO (or compatible) that make this a simpler task.
Hi Carsten53T, thanks for your reply, when doing macro I set focus to its closest point and move the camera to actually gain focus, this way it is at maximum magnification and the size of the subject remains constant so I can then stack several photos that have a shallow depth of field.
I see that the Mosfets I have are rated to 400v, does this mean that they wont switch and flow current at lower voltages? if not can you give some examples of transistors that would better suit my operation? ie Max voltage of 17v
Hi MichaelMeissner, thanks for the links, I'll have a better look when I finish work today, thats 2 votes for buying a motorshield..... one of the reasons I want to build my own drivers is so that I can leave the drivers attached to the motor circuits and use one Arduino for several projects. . . this is all a bit new to me so i'll probably learn the hard/expensive way
Hi Carsten53T, thanks for your reply, when doing macro I set focus to its closest point and move the camera to actually gain focus, this way it is at maximum magnification and the size of the subject remains constant so I can then stack several photos that have a shallow depth of field.
wow. My venu of diy-photo is another path: a bicycle-transportable 4m jib (photo for Meissner) :
I see that the Mosfets I have are rated to 400v, does this mean that they wont switch and flow current at lower voltages? if not can you give some examples of transistors that would better suit my operation? ie Max voltage of 17v
milutiche, pc's are just about 1's and 0's. It's the same about transistors .. give it a spark and it will reward you. It's not until you get down to the nitty gritty that it gets complicated. Someone else will have to help you. [at the uni book-store I shyed away from a 3-pounder named TRANSISTORS]
I've mentioned a dual h-bridge. It's a $5 component that does what you'r heading toward.
It's a component used in many drivers ($35). Even from the outset of a dual H-bridge, there's quite a way home for a newbie to a workable driver.
I would prepare myself to buy and then go 'test' your stuff to satisfy your worst curiousity .. and see what happens. But save the motor. How many cords sticks out of it 3, 4 or more? Do you know how steppers work?
I am in the process of working through the mechanics of a pan/tilt system for my D7000 for one button panos. I will be using 2 big drivers for it. I am considering the backpack in case I want to use the system with a truck (3 steppers total) like you are building allowing for some extremely complex time lapse movements.
Based on your model number (23KM-K339-G1V) I found this datasheet listing similar models. It does not include your specific model but it does tell us that the peak amperage is probably 2A.
Before a driver for your stepper can be recommended we need to know if it's unipolar or bipolar. How many wires does the stepper have coming out of it?
FWIW, I noticed this thread over in the programming section. It looks like that poster is a little further along in that he has some servos going to move the DSLR. You might consider pinging him for any pointers: http://arduino.cc/forum/index.php/topic,109784.0.html.
Hi people, My stepper motor is unipolar, I currently have a very basic working model of what I want to do using
1: a circuit board from a car speedo/odo (using the odo output to drive in bipolar configuration)
2: a square wave generator I threw together using a 555 timer, a 100k dual gang pot and a 330uf cap
3: a double poll, double throw switch to change direction.
I will try to draw up a schematic when I can find some spare time
Basically, what I really need to know is this, If I can configure the arduino to output trigers in the sequence I want to power the coils of the stepper motor, can I use the transistors I have listed to increase the current capability of the outputs? (centre tap of coils to regulated supply voltage and transistors switching the ground)
Again sorry if im not making much sense, my wife is due to give birth and i've got a heap on my mind
Flipping the direction of the current is easy to grasp, but difficult to impliment properly in the circuit. You not just has to switch transistor for each direction, but also involve a lot of rectifyer-diodes .. if for nothing else, then to prevent back-emf. How you'll connect that .. and controle it with logic circuits is worth $5 bucks not to get involved in imo. .. It would be good sport though, but someone else but me will have to deliver a quick-fix for an 'easy' setup.
milutiche,
I'm uncertain on understanding the diagram.
1 the coils and the way they are tied are not symmetric.
2 looking at a diagram of unipolar stepper I'm reminded of the coil-resistance + one resistor you add should add up to the voltage you intend to use and the max 2amp for the motor. Look at "Selecting a current limiting resistor" down the page in http://www.stepperworld.com/Tutorials/pgUnipolarTutorial.htm
3 I don't get the +5v .. that's the working-voltage of the board. Is it the intended voltage you want to use as power-source? In any way, you should be able to check how your IRF's works on a one to one (resistor + 5v + led and a pin high/low). The problem could be, that the IRF needs a relatively high/powerful input on the gate (compared to the meager output of a digital pin).
4 I think that it's the digital pins that's are to be protected from emf .. is it the pins that are marked Q
5 don't take the words from a newbie
Hello again,
1: sorry for the lack of symmetry, I copied the diagram from the internet and modified it using MS paint
2 & 3: I'm not sure of the required voltage for the stepper motor as I dont have a data sheet, so i'm not sure how to select a current limiting resistor, 5v was just an example
milutiche,
You should be able to assess/measure the resistance of each coil.
You never told us about the stepper .. does it 'look' like the ones at the link provided , and how many wires does it have?
As for transistors: I cannot read one that I use to controle a relay (BC 9-JC ..) .. googleing that gives transistors rated around 60v. I use 12V on it and controle it with a digital pin (it responds properly on 5V too).
And for the diodes .. My driver uses two for each end of a coil .. giving 8 in total - one of them may be an extra precaution.
When I started I had hacked a good handfull of transistors. I soon realized, that there were no consistant choise of gate/source/drain, so I made a small setup on my breadboard to test which pin is what .. and if I could controle them with a digital pin. Only some came out successful. Found the specs later recall vaguely that it probably were the high-voltage transistors that didn't work in my setup. I did also assamble some .. but the setup lost too much power (bwt the outcome looked like a christmas-tree)
I had use 4 pins on the arduino to drive a 12v stepper motor with a l293
with a l293 you need to use the stepper library, with a easy driver you just send fron arduino steps and dir. for another proyect, a sun tracker, i had use two hbride multiplexing 4 pins from arduino and 2 others pin to control the enable of eatch hbridge, as you see there are multiples options
