Electronics

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Revision as of 09:39, 22 March 2014 by Willadams (Talk | contribs) (Pololu A4988 Stepper Drivers)

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As noted on the Electronics Overview page, there are a number of components necessary to move the axes of a machine.

Microcontroller

A CNC machine needs to be able to take instructions to move to specific coordinates, and convert them into moment-by-moment, movement-by-movement signals for the Stepper Motors by sending electronic signals through the Stepper Drivers.

The typical choice for the ShapeOko is an Arduino, an inexpensive microcontroller board which provides a very good price for the needed precision.

E4.JPG

Stepper Shield

In addition to the microcontroller, the machine needs a system to take in the voltage necessary to move the motors and send it to the Stepper Motors.

Since, the gShield (formerly known as GrblShield) has become the standard choice --- this change was made to reduce the cost of the system and match its specifications with the machine's capabilities.

gShield (Arduino Shield for GRBL from Synthetos.com)

Please see the Advanced Electronics page for details on [Advanced_Electronics#Alternative_Stepper_Drivers|Alternative Stepper Drivers].

Stepper Drivers

It is necessary to take the signals from the Microcontroller and use it to apply the voltages from the power supply to the Stepper Motors --- the Stepper Drivers accomplish this. They may be soldered directly to the Stepper Shield, or installed into sockets, enabling replacement in the event of one being blown.

Assembling the electronics

Assemble the stepper driver shield If you purchased the Stepper Driver Shield as a kit, you'll need to solder the parts yourself.

Tip A great way to get the pins aligned properly is to actually plug the un-soldered header pins into the Arduino, and then set the driver shield on top. The pins will be aligned and allow you to easily solder them in place.

A complete video guide to assembling the buildlog shield is available http://j.mp/Lal92X

The stepper shield allows you to configure the drivers to use microstepping by adding jumpers to the pins along the center of the shield. We want to use microstepping on the x-axis and y-axis, but not the z-axis. Connect all three pairs of jumpers for X and Y to indicate 16 microsteps. Leave the pins "un-jumpered" for Z and A.

Stepper Shield from buildlog.net

Solder headers to the drivers You'll need to solder the headers to the drivers, too.

Tip You can use the same trick to solder the headers to the drivers and you did to solder the headers to the driver shield. Plug the headers into the driver shield and set the driver on top. The pins will be aligned and allow you to easily solder them in place.

Pololu A4988 stepper driver


Keeping things separated The shield sits extremely close to the Arduino. If it looks like components on the shield are going to touch the Arduino, you'll need to do something to keep them separated. Either insert some insulating material between them, or insert a set of headers between the Arduino and shield.

Driver shield sitting a little too close to the ArduinoDriver shield separated by an extra set of headers Driver shield separated by an extra set of headers

Alternative

Another option to help seperate the stepper shield from the arduino is to buy the Googly Eye Shield from evilmadscience.com!

Googly Eye Shield from Evil Mad Science

Power Supply

Any power supply that can produce 4.2A - 6A at 18-30v.

Note: We have successfully used 18V and 24v power supplies between 4A and 6A. Other power supplies may work. If you are unsure about anything related to powering the machine: STOP AND FIND A QUALIFIED PERSON TO ASSIST YOU!

I used an old power cord and connected the Load, Neutral, and Ground to the black, white, and green wires.

The COM connection on the power supply should be connected to the - on the driver shield. The +V connects to the + on the driver shield.

Power supply and arduino.JPG

Stepper Motors

The ShapeOko requires at least three stepper motors, one for each axis (Dual-drive Y-Axis is a popular upgrade and is now standard on the ShapeOko 2). The 58 oz-in motors listed are sufficient to drive the Shapeoko, but larger motors can be used. Forum Discussion. See Stepper Motors for more detail.

E1.JPG

Ventilation and Cooling

Two 12 volts DC fans in series can be connected directly to the power supply to cool everything as each one will have a voltage drop of around 12 volts. There has been some discussion in the Forums indicating this should not be done. Please research and consider the electrical aspects before doing this.

Further Alternatives

See also Advanced Electronics