Arduino powered electronic dividing head

[cfellows]

I've finally made a meaningful start on my Arduino powered dividing head the past few days.  Here's a little background for what I am doing.  First, the Arduino micro controller.  



Available online for under $30, has 32K memory, numerous analog and digital inputs and outputs, including serial and PWM.

Next, the Sainsmart LCD display and keyboard shield



This board is called a shield because it is pin compatible with and piggybacks right on top of the Arduino board.  It has a 2 line x 16 character display and 5 input keys plus a reset.  The keys are configured like the cursor keys on a PC having a left, right, up, and down as well as a select.  So, with this shield in place, the microcontroller can be used with only a power supply and doesn't have to be tethered to a computer.  The keys provide input and the LCD provides the display.

Here is the Sainsmart shield mounted on the Arduino...



The Sainsmart gets its power from the Arduino.

Another picture



The Arduino is programmed by hooking it up to your PC through a USB cable.  This also provides power to the Arduino board.  A free programming environment is available for the PC and allows you to develop programs in a language that looks almost exactly like C.  There are a host of standard libraries for interfacing to LCD's, keyboards, wireless, serial devices, and others.  You write the programs and compile them on the PC.  The compiler then automatically downloads the program to your Arduino.  Once the program is loaded on the Arduino, you can decouple it from the computer and run it off a separate power supply from 9 - 12 volts.  The program will stay in the Arduino memory even when the power is switched off.



So this is the basis for controlling my electronic dividing head.  The up and down arrow keys will be used to set the number of divisions I want, then the left and right arrow keys will be used to step forward or backward one division at a time.  The program I have written will calculate the number of stepper steps need for each division and keep track of the position I'm on.  The display shows the number of divisions and the current dividing head position.   I've got the software working for the user interface and calculations.  Now I need to develop the output side which will actually drive the stepper.  This should be pretty simple compared to the rest of it.

I have purchased a stepper driver board that is about the size of a postage stamp and will power a stepper of up to 2 amps, 35 volts.  I still have to select the stepper motor I want to use and build the mechanical part of the dividing head.  Still have a few challenges ahead of me.

Chuck

[nel2lar]

Chuck
Very interesting, I will be keeping up with your progress. Maybe something I would like to make.
Nelson Collar

[cfellows]

Thanks, Nelson.

Here's a video of the preliminary setup.  This doesn't include the dividing head, but does have the Arduino, the stepper motor driver and the stepper.  You can see how I'm able to control the divisions per rotation of the stepper.  I can change the program to work with any resolution by changing one variable.

http://www.youtube.com/watch?v=ZRcPKY3APM0&feature=youtu.be

Chuck

[raynerd]

Chuck, will you be releasing the source code for this as I`d love to take a look at it? I have about ten Arduino Duemilanove at work that I use with the kids and they are fantastic. So much support on the web and so many projects.
I`ve always been really interested in Kwackers rotary table and have made a few of these now but one based on the Arduino has always interested to me. I`ve also got Polulu drivers for my RepRap build so have all these parts in stock!

Excellent idea and hope you do decide to release the source!

Chris

[cfellows]

Here's a video of my dividing head in operation.  I took the slack out of the belt and put a makeshift heatsink on the stepper driver chip so now it works consistently and reliably.  The holding power of the stepper is enough for me to satisfactorily tighten the collet chuck with a crescent wrench.  I can get it to slip with the wrench but not easily.

http://www.youtube.com/watch?v=ODf9sJzXHzA&list=UUZB8pRNp9Plbd0-T9RmyR9g&index=1&feature=plcp

I've got an Arduino Nano on order that I plan to use in a finished version of this dividing head.  I'll also use a separate LCD display and input keys to put the whole thing into an attractive and more robust case.  I believe this is going to be a really nice little addition to my shop.  Next I might tackle my rotary table. 

Chuck

[revwarguy]

Hello Chuck,

I was really interested to see this, as I had been thinking of something along those lines.  Couple of questions:

1. Is the rest torque of the stepper enough to withstand milling forces, or do you think some kind of spindle lock or brake is needed once the rotation position is achieved?

2. In the youtube video where you machine the pentagonal cut or the gears, what did you use for the main collet/spindle that is in your vise?  Scratch built or ??

3.  Have you decided to share the arduino source?  I would love to play with it.  (I am an old C programmer and have programmed the arduino, so I won't bother you with any follow up questions about it!)

4. I am looking at this in order to make some larger XL timing belt gears in order to make a belt drive for a split ring telescope mount - imagine my surprise when I saw all your telescope work on your website!  Did you make the gears for this, or buy them?  (kind of a chicken or egg problem!)

5. Would you still stay with the polulo stepper driver, or do something else with microstepping, like EasyDriver (sparkfun), or go with something heavier in terms of power for more holding force?

Anyway, thanks for your work on this, and I would like to encourage you to update your very informative website!!  I know what I am asking here, as I maintain some of those myself.