Building a Stepper Motor Driver Board

Overview

A bipolar stepper motor driver board translates low-current STEP and DIR logic pulses from a microcontroller into high-current, PWM-chopped H-bridge coil currents (A1/A2 and B1/B2) capable of driving NEMA 17 and NEMA 23 stepper motors with precise microstepping.

In this tutorial, you will design a complete stepper motor driver carrier board (modeled around a standard dual H-bridge microstepping driver IC such as the A4988 / DRV8825) using tscircuit.

export default () => (
  <board width="42mm" height="28mm">
    {/* 6-Pin Logic Control Header */}
    <pinheader
      name="J_CTRL"
      pinCount={6}
      pitch="2.54mm"
      footprint="pinrow6"
      pinLabels={["VDD", "GND", "STEP", "DIR", "MS1", "EN"]}
      pcbX={-17}
      pcbY={0}
      pcbRotation="90deg"
      schX={-8}
      schY={0}
    />

    {/* Bipolar Stepper Motor Driver IC */}
    <chip
      name="U1"
      footprint="tssop16"
      pinLabels={{
        pin1: ["STEP"],
        pin2: ["DIR"],
        pin3: ["MS1"],
        pin4: ["EN"],
        pin5: ["RST"],
        pin6: ["VDD"],
        pin7: ["GND1"],
        pin8: ["SENSE_A"],
        pin9: ["SENSE_B"],
        pin10: ["GND2"],
        pin11: ["VMOT"],
        pin12: ["B2"],
        pin13: ["B1"],
        pin14: ["A2"],
        pin15: ["A1"],
        pin16: ["SLP"],
      }}
      schPortArrangement={{
        leftSide: {
          pins: ["VDD", "STEP", "DIR", "MS1", "EN", "RST", "SLP", "GND1"],
          direction: "top-to-bottom",
        },
        rightSide: {
          pins: ["VMOT", "A1", "A2", "B1", "B2", "SENSE_A", "SENSE_B", "GND2"],
          direction: "top-to-bottom",
        },
      }}
      pcbX={0}
      pcbY={0}
      schX={0}
      schY={0}
    />

    {/* 6-Pin Motor Coil & High-Voltage Supply Header */}
    <pinheader
      name="J_MOT"
      pinCount={6}
      pitch="2.54mm"
      footprint="pinrow6"
      pinLabels={["VMOT", "GND", "A1", "A2", "B1", "B2"]}
      pcbX={17}
      pcbY={0}
      pcbRotation="90deg"
      schX={8}
      schY={1}
    />

    {/* Decoupling Capacitors */}
    <capacitor
      name="C_VDD"
      capacitance="100nF"
      footprint="0603"
      pcbX={-9}
      pcbY={8}
      schX={-4.5}
      schY={4}
    />
    <capacitor
      name="C_VMOT"
      capacitance="47uF"
      footprint="1210"
      pcbX={9}
      pcbY={8}
      schX={4.5}
      schY={4.5}
    />

    {/* Pull-Up on RST/SLP and Low-Ohm Current-Sense Resistors */}
    <resistor
      name="R_SLP"
      resistance="10k"
      footprint="0603"
      pcbX={-9}
      pcbY={-8}
      schX={-4.5}
      schY={-3.5}
    />
    <resistor
      name="R_SA"
      resistance="0.1"
      footprint="1206"
      pcbX={8}
      pcbY={-6}
      schX={3.5}
      schY={-4}
    />
    <resistor
      name="R_SB"
      resistance="0.1"
      footprint="1206"
      pcbX={8}
      pcbY={-10}
      schX={5.5}
      schY={-4}
    />

    {/* Logic Power & Control Connections */}
    <trace from=".J_CTRL > .VDD" to="net.VDD" />
    <trace from=".J_CTRL > .GND" to="net.GND" />
    <trace from=".U1 > .VDD" to="net.VDD" />
    <trace from=".U1 > .GND1" to="net.GND" />
    <trace from=".U1 > .GND2" to="net.GND" />
    <trace from=".J_CTRL > .STEP" to=".U1 > .STEP" />
    <trace from=".J_CTRL > .DIR" to=".U1 > .DIR" />
    <trace from=".J_CTRL > .MS1" to=".U1 > .MS1" />
    <trace from=".J_CTRL > .EN" to=".U1 > .EN" />

    {/* Tie RST and SLP high via 10k pull-up for active operation */}
    <trace from=".R_SLP > .pin1" to="net.VDD" />
    <trace from=".R_SLP > .pin2" to=".U1 > .RST" />
    <trace from=".U1 > .SLP" to=".U1 > .RST" />

    {/* Decoupling Capacitors */}
    <trace from=".C_VDD > .pos" to="net.VDD" />
    <trace from=".C_VDD > .neg" to="net.GND" />
    <trace from=".C_VMOT > .pos" to="net.VMOT" />
    <trace from=".C_VMOT > .neg" to="net.GND" />

    {/* Current-Sense Resistors to Ground */}
    <trace from=".U1 > .SENSE_A" to=".R_SA > .pin1" />
    <trace from=".R_SA > .pin2" to="net.GND" />
    <trace from=".U1 > .SENSE_B" to=".R_SB > .pin1" />
    <trace from=".R_SB > .pin2" to="net.GND" />

    {/* Motor Power & H-Bridge Coil Outputs */}
    <trace from=".J_MOT > .VMOT" to="net.VMOT" />
    <trace from=".J_MOT > .GND" to="net.GND" />
    <trace from=".U1 > .VMOT" to="net.VMOT" />
    <trace from=".U1 > .A1" to=".J_MOT > .A1" />
    <trace from=".U1 > .A2" to=".J_MOT > .A2" />
    <trace from=".U1 > .B1" to=".J_MOT > .B1" />
    <trace from=".U1 > .B2" to=".J_MOT > .B2" />
  </board>
)

---

Components Needed (Bill of Materials)

Reference	Component	Value / Package	Purpose
U1	Bipolar Stepper Driver IC	A4988 / DRV8825 (tssop16)	Dual full-bridge MOSFET driver with built-in microstepping translator
J_CTRL	6-Pin Logic Header	2.54mm pitch (pinrow6)	Connects microcontroller VDD (3.3V/5V), GND, STEP, DIR, MS1, EN
J_MOT	6-Pin Motor & Power Header	2.54mm pitch (pinrow6)	Connects motor supply VMOT (8V–35V), GND, and coils A1, A2, B1, B2
R_SA, R_SB	Current-Sense Resistors	0.1Ω (1206, 0.5W+)	Measures coil current for the internal PWM constant-current chopper
R_SLP	Reset/Sleep Pull-Up Resistor	10kΩ (0603)	Holds RST and SLP high to keep the driver awake by default
C_VDD	Logic Bypass Capacitor	100nF (0603)	Decouples the 3.3V/5V digital logic supply
C_VMOT	Bulk Motor Supply Capacitor	47uF (1210, 50V rated)	Absorbs inductive kickback and supplies peak coil switching currents

---

How a Chopper Stepper Motor Driver Works

1. STEP and DIR Interface

Instead of energizing individual H-bridge transistors from software, a microstepping translator IC advances its internal sine/cosine current table on every rising edge of the STEP pin. The logic level on DIR (HIGH or LOW) determines whether the motor shaft rotates clockwise or counter-clockwise.

2. Constant-Current PWM Regulation (R_SA and R_SB)

Stepper motor coils have low winding resistance (1Ω–3Ω). Driving them directly from 12V or 24V minimizes inductive rise time at high RPMs, but requires active current limiting to prevent overheating. The driver monitors the voltage across low-value sense resistors (R_SA = 0.1Ω, R_SB = 0.1Ω). For an A4988-class driver, the peak trip current I_MAX is set by:

I_MAX = V_REF / (8 * R_SENSE)

With R_SENSE = 0.1Ω and V_REF = 0.8V, the driver regulates each coil to I_MAX = 0.8V / 0.8Ω = 1.0A.

---

Step-by-Step Circuit Design in tscircuit

Step 1: Define the Stepper Motor Driver IC (U1)

We start by placing the 16-pin driver chip (U1) with logic inputs on the left side of the schematic symbol and high-current motor pins (VMOT, A1, A2, B1, B2, SENSE_A, SENSE_B) on the right side.

export default () => (
  <board width="28mm" height="22mm">
    <chip
      name="U1"
      footprint="tssop16"
      pinLabels={{
        pin1: ["STEP"],
        pin2: ["DIR"],
        pin3: ["MS1"],
        pin4: ["EN"],
        pin5: ["RST"],
        pin6: ["VDD"],
        pin7: ["GND1"],
        pin8: ["SENSE_A"],
        pin9: ["SENSE_B"],
        pin10: ["GND2"],
        pin11: ["VMOT"],
        pin12: ["B2"],
        pin13: ["B1"],
        pin14: ["A2"],
        pin15: ["A1"],
        pin16: ["SLP"],
      }}
      schPortArrangement={{
        leftSide: {
          pins: ["VDD", "STEP", "DIR", "MS1", "EN", "RST", "SLP", "GND1"],
          direction: "top-to-bottom",
        },
        rightSide: {
          pins: ["VMOT", "A1", "A2", "B1", "B2", "SENSE_A", "SENSE_B", "GND2"],
          direction: "top-to-bottom",
        },
      }}
    />
  </board>
)

Step 2: Add Current-Sense Resistors and Power Decoupling

Next, we connect the two 0.1Ω 1206 current-sense resistors (R_SA, R_SB) between SENSE_A/SENSE_B and net.GND, pull RST and SLP high to net.VDD via R_SLP (10kΩ), and add decoupling capacitors C_VDD (100nF) and C_VMOT (47uF).

export default () => (
  <board width="34mm" height="26mm">
    <chip
      name="U1"
      footprint="tssop16"
      pinLabels={{
        pin1: ["STEP"],
        pin2: ["DIR"],
        pin3: ["MS1"],
        pin4: ["EN"],
        pin5: ["RST"],
        pin6: ["VDD"],
        pin7: ["GND1"],
        pin8: ["SENSE_A"],
        pin9: ["SENSE_B"],
        pin10: ["GND2"],
        pin11: ["VMOT"],
        pin12: ["B2"],
        pin13: ["B1"],
        pin14: ["A2"],
        pin15: ["A1"],
        pin16: ["SLP"],
      }}
      schPortArrangement={{
        leftSide: {
          pins: ["VDD", "STEP", "DIR", "MS1", "EN", "RST", "SLP", "GND1"],
          direction: "top-to-bottom",
        },
        rightSide: {
          pins: ["VMOT", "A1", "A2", "B1", "B2", "SENSE_A", "SENSE_B", "GND2"],
          direction: "top-to-bottom",
        },
      }}
      schX={0}
      schY={0}
    />

    <capacitor name="C_VDD" capacitance="100nF" footprint="0603" schX={-4.5} schY={4} />
    <capacitor name="C_VMOT" capacitance="47uF" footprint="1210" schX={4.5} schY={4.5} />
    <resistor name="R_SLP" resistance="10k" footprint="0603" schX={-4.5} schY={-3.5} />
    <resistor name="R_SA" resistance="0.1" footprint="1206" schX={3.5} schY={-4} />
    <resistor name="R_SB" resistance="0.1" footprint="1206" schX={5.5} schY={-4} />

    <trace from=".U1 > .VDD" to="net.VDD" />
    <trace from=".U1 > .VMOT" to="net.VMOT" />
    <trace from=".U1 > .GND1" to="net.GND" />
    <trace from=".U1 > .GND2" to="net.GND" />

    <trace from=".R_SLP > .pin1" to="net.VDD" />
    <trace from=".R_SLP > .pin2" to=".U1 > .RST" />
    <trace from=".U1 > .SLP" to=".U1 > .RST" />

    <trace from=".C_VDD > .pos" to="net.VDD" />
    <trace from=".C_VDD > .neg" to="net.GND" />
    <trace from=".C_VMOT > .pos" to="net.VMOT" />
    <trace from=".C_VMOT > .neg" to="net.GND" />

    <trace from=".U1 > .SENSE_A" to=".R_SA > .pin1" />
    <trace from=".R_SA > .pin2" to="net.GND" />
    <trace from=".U1 > .SENSE_B" to=".R_SB > .pin1" />
    <trace from=".R_SB > .pin2" to="net.GND" />
  </board>
)

Step 3: PCB Layout and High-Current Routing Guidelines

When laying out a stepper driver PCB, keep these power-electronics layout rules in mind:

1. Short Sense-Resistor Ground Paths: Place R_SA and R_SB (1206) close to the driver IC with direct, low-inductance connections to GND so switching spikes do not falsely trip the current comparator.
2. Place C_VMOT Close to VMOT and GND: The 47uF bulk capacitor handles rapid current reversals when the H-bridges chop coil current.
3. Separate Logic and Motor Sides: Place the microcontroller header (J_CTRL) on the left edge of the board and the high-voltage motor header (J_MOT) on the right edge.

export default () => (
  <board width="42mm" height="28mm">
    <pinheader
      name="J_CTRL"
      pinCount={6}
      pitch="2.54mm"
      footprint="pinrow6"
      pinLabels={["VDD", "GND", "STEP", "DIR", "MS1", "EN"]}
      pcbX={-17}
      pcbY={0}
      pcbRotation="90deg"
      schX={-8}
      schY={0}
    />
    <chip
      name="U1"
      footprint="tssop16"
      pinLabels={{
        pin1: ["STEP"],
        pin2: ["DIR"],
        pin3: ["MS1"],
        pin4: ["EN"],
        pin5: ["RST"],
        pin6: ["VDD"],
        pin7: ["GND1"],
        pin8: ["SENSE_A"],
        pin9: ["SENSE_B"],
        pin10: ["GND2"],
        pin11: ["VMOT"],
        pin12: ["B2"],
        pin13: ["B1"],
        pin14: ["A2"],
        pin15: ["A1"],
        pin16: ["SLP"],
      }}
      pcbX={0}
      pcbY={0}
      schX={0}
      schY={0}
    />
    <pinheader
      name="J_MOT"
      pinCount={6}
      pitch="2.54mm"
      footprint="pinrow6"
      pinLabels={["VMOT", "GND", "A1", "A2", "B1", "B2"]}
      pcbX={17}
      pcbY={0}
      pcbRotation="90deg"
      schX={8}
      schY={1}
    />
    <capacitor
      name="C_VDD"
      capacitance="100nF"
      footprint="0603"
      pcbX={-9}
      pcbY={8}
      schX={-4.5}
      schY={4}
    />
    <capacitor
      name="C_VMOT"
      capacitance="47uF"
      footprint="1210"
      pcbX={9}
      pcbY={8}
      schX={4.5}
      schY={4.5}
    />
    <resistor
      name="R_SLP"
      resistance="10k"
      footprint="0603"
      pcbX={-9}
      pcbY={-8}
      schX={-4.5}
      schY={-3.5}
    />
    <resistor
      name="R_SA"
      resistance="0.1"
      footprint="1206"
      pcbX={8}
      pcbY={-6}
      schX={3.5}
      schY={-4}
    />
    <resistor
      name="R_SB"
      resistance="0.1"
      footprint="1206"
      pcbX={8}
      pcbY={-10}
      schX={5.5}
      schY={-4}
    />

    <trace from=".J_CTRL > .VDD" to="net.VDD" />
    <trace from=".J_CTRL > .GND" to="net.GND" />
    <trace from=".U1 > .VDD" to="net.VDD" />
    <trace from=".U1 > .GND1" to="net.GND" />
    <trace from=".U1 > .GND2" to="net.GND" />
    <trace from=".J_CTRL > .STEP" to=".U1 > .STEP" />
    <trace from=".J_CTRL > .DIR" to=".U1 > .DIR" />
    <trace from=".J_CTRL > .MS1" to=".U1 > .MS1" />
    <trace from=".J_CTRL > .EN" to=".U1 > .EN" />
    <trace from=".R_SLP > .pin1" to="net.VDD" />
    <trace from=".R_SLP > .pin2" to=".U1 > .RST" />
    <trace from=".U1 > .SLP" to=".U1 > .RST" />
    <trace from=".C_VDD > .pos" to="net.VDD" />
    <trace from=".C_VDD > .neg" to="net.GND" />
    <trace from=".C_VMOT > .pos" to="net.VMOT" />
    <trace from=".C_VMOT > .neg" to="net.GND" />
    <trace from=".U1 > .SENSE_A" to=".R_SA > .pin1" />
    <trace from=".R_SA > .pin2" to="net.GND" />
    <trace from=".U1 > .SENSE_B" to=".R_SB > .pin1" />
    <trace from=".R_SB > .pin2" to="net.GND" />
    <trace from=".J_MOT > .VMOT" to="net.VMOT" />
    <trace from=".J_MOT > .GND" to="net.GND" />
    <trace from=".U1 > .VMOT" to="net.VMOT" />
    <trace from=".U1 > .A1" to=".J_MOT > .A1" />
    <trace from=".U1 > .A2" to=".J_MOT > .A2" />
    <trace from=".U1 > .B1" to=".J_MOT > .B1" />
    <trace from=".U1 > .B2" to=".J_MOT > .B2" />
  </board>
)

---

Driving the Stepper Motor from Firmware

Connect J_CTRL to your microcontroller (STEP -> GPIO 2, DIR -> GPIO 3, EN -> GND) and connect a 12V–24V supply plus your bipolar stepper motor coils to J_MOT:

const int STEP_PIN = 2;
const int DIR_PIN  = 3;
const int STEPS_PER_REV = 200; // 1.8 deg/step NEMA 17 motor in full-step mode

void setup() {
  pinMode(STEP_PIN, OUTPUT);
  pinMode(DIR_PIN, OUTPUT);
}

void stepMotor(int steps, bool clockwise, int pulseDelayUs) {
  digitalWrite(DIR_PIN, clockwise ? HIGH : LOW);
  for (int i = 0; i < steps; i++) {
    digitalWrite(STEP_PIN, HIGH);
    delayMicroseconds(pulseDelayUs);
    digitalWrite(STEP_PIN, LOW);
    delayMicroseconds(pulseDelayUs);
  }
}

void loop() {
  // Rotate 1 full revolution clockwise
  stepMotor(STEPS_PER_REV, true, 800);
  delay(500);

  // Rotate 1 full revolution counter-clockwise
  stepMotor(STEPS_PER_REV, false, 800);
  delay(500);
}