Laser Controller Tutorial Part 3: Wiring Motors to Drivers and Calculating Steps Per Inch
In this series we'll be examining how to install the laser control unit. We will start with the basic wiring and move all the way up to software and functions.
At this point we've connected the power supply to laser controller and we also have the drivers connected. Now we are going to connect the motors to the drivers and configure them.
We're using NEMA 23 100oz-in motors. Normally you would wire these motors via a cable to plug into a connector, but in this demonstration we will be connecting the wires directly to the drivers.
Visit BuildYourCNC's page on the NEMA 23 motor to find the wiring diagram. We're going to use 4 terminals here, so we will not be using the center leads. We see the specification for the amps is 3.0 amps so we will need to set the driver at max amp capacity.
Don't worry too much about the voltage specification. The more voltage we apply to this motor the more velocity we can achieve on the motor.
The first thing we'll do is to cut the tips on the wires we don't be using so the bare wires won't make contact with anything we don't want it to. Remember, we're not using the center lead wires (Yellow and White).
The diagram calls for black and green to A. We'll wire the black to A+ and the green to A-. On the B coil, red will go to B+ and blue goes to B-. Repeat this process for the other motor and driver.
Now that both motors and drivers are connected, we will begin to configure them for proper operation. To set the dipswitches, refer to the table on the driver. We are using the 3.0 amp specification, so we'll set 5, 6, and 7 to "1" or "up".
To configure the microstepping, you need to consider the mechanics of what you're using to calculate steps per inch. We'll now look at the steps per inch formula.
We need the following information for calculate Steps / Inch
In this example we'll be using a 1/2" diameter 5-start lead screw.
For the specification of 10 / 5 starts we have 2 turns per inch. So we have 1/2 as our answer.
Formula Steps / Inch = (motor steps x microsteps per step) / (inches / revolution)
Now we will use algebra to isolate the variable we are looking for.
For 1000 steps per inch:
Steps Per Inch: 1000 * 1/2 = / motor steps (200)
500 / 200
Answer = 2.5 microsteps.
Because we don't have 2.5 microsteps as an option, we'll use 8 (remember this is 1/8th microstepping). So if we replace 2.5 with 8 and work backwards steps per inch will now become 3200.
The formula for drive pulley will be similar except we will be using the pitch and teeth of the drive pulley instead of the turns and starts of the lead screw.
Now that we know we want to use 1/8th microstepping, we see it is 0, 0, 1 on the chart. So we move the 3 to "1" or "up" to achieve 1/8th microstepping.