Re: [CAD_CAM_EDM_DRO] Motorising a rotary table

On 06/25/2013 06:08 PM, michael_s@... wrote:

> Doing the mechanical is not a problem for me and even the wiring if I know what to do. Please can anyone help me with information of what I need to buy and how to wire things up. The handwheel to table ratio is 40:1 and I need to be able to control the table rotation from zero to 5 rpm.
>
> I envisage controlling the motor either from a switch or a foot pedal. It would be handy if the motor could cause the table to rotate once and then stop but this isn't vital.

Let's start with some silliness: 40:1 gear ratio and 5 RPM means the
motor needs to only do 200 RPM. That is stepper territory unless you
need real precision. First, take off the handwheel and see what the
shaft looks like, this may be a show stopper if no coupling will work.
Now use a torque meter to see just how much torque is needed. If no
torque meter, a lever arm and a spring scale will work. If the torque
needs are low enough, a size 17 motor may be enough, and the controller
for that can be an Arduino and a low end (like Pololu) motor controller,
a very simple, cheap setup.

I will assume you can make a plate to mount the motor and one to attach
to the rotary table. Spacers will set the distance between to match the
coupler.

If you want neat, a 1602 style display (16 characters by 2 lines, a
really common, cheap unit), will let you show the current position and
the menu items (e.g. 1 turn, 36 degrees, etc.) See
http://www.ebay.com/itm/LCD-1602-16-2-display-Keypad-Shield-for-Arduino-Duemilanove-/190836358425?pt=LH_DefaultDomain_0&hash=item2c6ebbbd19
for a shield with the display and all the keys you will need, you could,
of course, go with a numeric keypad, but that is overkill. Add a wall
wart and you will be all set. Cost? Display and keys: under $7 (see
above), a motor shield for under $7.00 (see
http://www.ebay.com/itm/1-New-Motor-Drive-Shield-Expansion-Board-L293D-for-Arduino-Mega-UNO-Duemilanove-/251099630342?pt=LH_DefaultDomain_0&hash=item3a76b44b06),
an Arduino for under $15.00 (see
http://www.ebay.com/itm/Funduino-Duemilanove-Board-2009-ATmega328p-pu-compatible-Arduino-usb-cable-/200935749557?pt=LH_DefaultDomain_0&hash=item2ec8b437b5),
and a wall wart for $10 (see
http://www.ebay.com/itm/AC-Power-Adapter-12V-DC-Supply-2a-amp-regulated-Wall-Wart-Charger-5-5-mm-2-1-mm-/171056467593?pt=Laptop_Adapters_Chargers&hash=item27d3c28e89),
put it in a box and wire it. You will need to write the Arduino code
(which is simple) and it will need a home switch (also simple) if you
want to do repeatable stuff. I would guess well under $50 for the
driver and a $15 stepping motor (see
http://www.ebay.com/itm/1-PC-NEMA-17-CNC-Step-Stepping-Stepper-Motor-34mm-0-4A-40-0oz-in-Bipolar-/121051250999?pt=LH_DefaultDomain_0&hash=item1c2f378137)
plus coupler, etc. should keep it well under $100.00

Is that cheap enough?

Dave 8{)

--

"A word to the wise ain't necessary - it's the stupid ones that need the
advice."

Bill Cosby