Anet A8 Reduce Stepper Current

thingiverse

Important ================ Be cautious, attempting this may result in damaging your board or stepper motor(s). To proceed, you must be able to solder resistors onto your board and understand the marked parts on the schematic. Problem Identification ---------------------- If you own an older Anet A8 board, chances are you can't adjust stepper currents for all axes, only the z-axis steppers. For more information, visit https://3dprint.wiki/reprap/anet/electronics/mainboard. The default current on the Anet A8 is quite high, causing stepper motors to heat up and produce excessive noise. Solution Overview ----------------- To address this issue, you'll need to modify the board's resistor values. This involves replacing 15kohm resistors with smaller ones using a voltage divider calculator. Step-by-Step Instructions ------------------------- 1. Locate the Anet A8 schematics at https://github.com/ralf-e/ANET-3D-Board-V1.0. 2. Observe that stepper drivers use a voltage divider consisting of 100kohm and 15kohm resistors. 3. By replacing the 15kohm resistor with a smaller one, you can reduce the current sent to the steppers. 4. Use the voltage divider calculator (http://www.ohmslawcalculator.com/voltage-divider-calculator) to determine the desired resistance value. Determining Desired Resistance ------------------------------ 1. Note that if you input the original values (5V, 100kohm, 15kohm), the calculator will output 0.652V, which is also visible on the schematic. 2. To get the desired voltage, test with the z-axis using a potentiometer connected to the z-driver. Adjust the voltage until the axis moves properly and measure the voltage of the potentiometer to ground. Important Safety Precautions --------------------------- 1. Before modifying the z-driver voltage, ensure you've measured the original voltage and recorded it for future reference. 2. Reduce the voltage at least to 0.65V before testing your x- or y-axis on the z-driver, as the z-driver is set to a higher voltage by default. Calculating Required Resistance ------------------------------ 1. Once you've determined the desired voltage, use the voltage divider calculator to calculate the required resistance. 2. For example, with an output voltage of 0.4V, the desired resistance would be approximately 8.7kohm. Replacing or Adding Resistors --------------------------- 1. You can either replace the 15kohm resistor with a resistor of the calculated size (e.g., 8.7kohms) or add a second resistor in parallel. 2. If using a single resistor, simply replace the original one with the new value. 3. To add a second resistor, use the parallel resistance calculator (http://www.sengpielaudio.com/calculator-paralresist.htm) to determine the required size. Important Safety Considerations ------------------------------ 1. After modifying the resistor values, ensure you obtain the correct resistance to ground by unplugging the stepper motors and board. 2. If the measured resistance is too high or there's no connection at all, you risk damaging your drivers or stepper motors. Note: I haven't tested adding resistors in parallel; instead, I replaced the original resistor. However, in hindsight, adding a second resistor might be safer than replacing the original one.