# Current calibration procedure on the X-Controller using vref?

Does anyone have a write up on the procedure for setting the stepper current using the voltage reference points on the X-Controller? Does it need to be done under load or just with the motors moving?

I haven’t seen any documentation on the X-controller circuit board.

If you can find out what the correct setting is then you don’t have to have any load or motor movement to set Vref.

You will need two pieces of information. The driver chip that was used on the board and the value of the current sense resistor so that you can look at the driver chip data sheet to get the formula to calculate the correct Vref setting for a particular current.

From the X-Controller assembly instructions:

The potentiometers on the controller board allow you to control the
maximum current to the motors. Clockwise increases the current and
counter-clockwise decreases the current. Current ratings are different
for NEMA 17 (1.6A) and NEMA
23 (2.8A) stepper motors and need to be set accordingly. The slot
between the dots on the gray actuator is the pointer, and can be
adjusted based on the diagram on the controller board.
For those users who would like to know the current more precisely,
you can measure the amount of voltage on the reference and ground test
points. Use the formula (I = ref * 2.13) on the diagram to determine
the current. For example, if you measure 1V you get 2.13 amps.

So if I = 2.8 = ref * 2.13
then ref = 1.314V which I believe is the voltage I’m shooting for, I just wasn’t sure under
what conditions I should do this.

Just noticed, you said the motor doesn’t even have to be moving? I can just connect to the test points with the machine powered, adjust the current pot till I get the desired voltage and then I’m done? That sounds easy.

The motors do not have to be connected.

The PCB has a legend on it. It lists the voltage to current equation, but also has a simple legend of the pot to say what current you will get for multiple points along the rotation.

Don’t be afraid to run the little extra current into the motors. The idle current reduction feature does a great job of keeping the motors cool.

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Does anyone know how the GRBL “Step idle delay” feature and the X-Controller Stepper Driver Shield idle current reduction feature are related?

Are these completely separate things, or does GRBL control the idle current feature on the driver shield circuit board?

The Grbl feature is unrelated to the X-Controller feature.

Grbl Step Idle Delay turns off all the stepper drivers a set number of milliseconds after Grbl enters idle mode. We do not recommend using that on X-Carves. It is best to leave the motors on or position may be lost. X-Controller does support it though.

The X-Controller idle reduction feature is different. It reduces current rather than stops current. It is also independent for each axis. The X and Y can still be moving and the Z could enter current reduction. Stepper motors lose torque with speed, so even if they have reduced torque at idle, they may actually have more torque than the running, full current, motors. This feature results in lower average motor temperature, so higher full current settings can be used to improve performance.

Hi Steve … could you please show me how the smount of voltage on the reference and ground test point … ? I have Nema 23 with 2.0A and i set the pot in the x-controller to 2.0 based on the refetence on the board … i need to check the current before testing my x-carve …

Look here for the current calibration instructions just above step 2. The third picture on the right shows the location of the test points to measure the voltage, you measure between either xref, yref, or zref and gnd. They are each just to the right of the potentiometer.

xref, yref, zref, gnd

Could you please clearify more … i am not able to figure out the pins to test …

Thanks all … i got it … i will test it now …

I’m trying to help. I couldn’t locate the test points for setting the voltage/amperage of the X-Controller until I got my magnifying glass out. On the ZYZ Axis PCB see test points TP1 through TP6. TP4 is ground and TP1-TP3 are X, Y, & Z voltage test points. I have tried to take a picture identifying these. There are also TP5 and TP6. If anyone knows what these are for I would appreciate an explanation.

Also does anyone know how to adjust the movement distance or if there is a movement adjustment on the X-Controller?

Hope this helps.
Van

I responded to you on the thread where you asked about 18 vs 20 tooth pulleys…

TP5 is the +5 volt supply.
TP6 is the motor voltage.

Grbl has a steps/mm adjustment which you can use to fine tune the distance the machine moves along each axis.

\$100,\$101,\$102 X,Y,Z

Sorry the fingers didn’t show up better. There or six of them. 4 in red and 2 in blue.

I’m old and slow. My XYZ movement appear to be a percentage of x input. If I adjust the mm movement (\$100=10) then X moves approximately 8.16mm. I put 18 tooth belt pulleys on so I have ordered 20 tooth pulleys. Is there a way to adjust the XYZ movement in percentage?

Take a look at this video:

Calibration

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