| A4988 | DRV8825 | TB6612FNG | |
|---|---|---|---|
| Drives | One bipolar stepper | One bipolar stepper | Two DC motors, or one small bipolar stepper |
| Motor supply | 8–35 V | 8.2–45 V | 4.5–13.5 V |
| Current | About 1 A per coil without a heatsink; up to 2 A with good cooling | About 1.5 A per coil without a heatsink; up to 2.2 A with cooling | 1.2 A per channel continuous, 3.2 A peak |
| Current limiting | Yes — set with the Vref trimmer | Yes — set with the Vref trimmer | No |
| Microstepping | Up to 1/16 | Up to 1/32 | None in hardware (full/half step in code) |
| Control | STEP + DIR | STEP + DIR | IN1/IN2 + PWM per channel, STBY |
| Logic level | 3.3 V or 5 V | 3.3 V or 5 V | 2.7–5.5 V |
| Typical price in India | ₹80–150 | ₹120–250 | ₹150–300 |
The A4988 and DRV8825 are the small “stepstick” boards from 3D printers; the TB6612FNG is a dual H-bridge for DC motors. They overlap only for small steppers. Current figures follow the Pololu carrier boards most clones copy; clone quality varies, so treat them as upper limits. Prices are indicative.
A4988 vs DRV8825: very similar, a few real differences
Both take a STEP pulse per step and a DIR level, and both limit coil current — which lets you run a stepper from a higher voltage for better torque at speed.
- DRV8825 handles more voltage and current and offers 1/32 microstepping. It’s the upgrade when an A4988 runs hot.
- A4988 is cheaper, and many find it quieter at low speeds.
- Pin compatible in most sockets — but the trimmer sits in a different corner, so check orientation before plugging in.
- The DRV8825 needs a slightly longer minimum STEP pulse (about 2 µs); most libraries already handle this.
Setting the current (Vref) — don’t skip this
With the motor connected and powered, measure the voltage between the trimmer and GND:
- A4988: current limit = Vref ÷ (8 × R_sense). Clones use 0.1 Ω, 0.068 Ω or 0.05 Ω sense resistors — read yours (R100 = 0.1 Ω) before calculating.
- DRV8825 (0.1 Ω sense resistors): current limit = Vref × 2.
Start at about 70 % of your motor’s rated current and raise it only if steps are missed.
Rules that save drivers
- Never connect or disconnect the motor while powered. The voltage spike kills the driver instantly.
- Put a 100 µF electrolytic capacitor across VMOT and GND, close to the driver.
- Add a small heatsink and airflow above about 1 A.
TB6612FNG: for DC motors
- Drives two DC motors forward, reverse and speed via PWM — the usual choice for small robots with yellow “BO” gear motors.
- MOSFET outputs waste far less voltage than the old L298N — see L298N vs TB6612FNG.
- No current limiting. It can run a small bipolar stepper in full or half steps, but only if the motor’s coil resistance keeps the current within 1.2 A at your supply voltage.
What about the 28BYJ-48?
That cheap 5 V geared stepper is unipolar and comes with a ULN2003 board — it doesn’t need any of these. See the ULN2003 stepper page and the curtain opener project.
Verdict
| Motor | Pick |
|---|---|
| NEMA 17 stepper, up to about 1 A per coil | A4988 |
| NEMA 17 above 1 A, or 24 V+ supply, or smoother motion | DRV8825 |
| Two DC gear motors on a robot | TB6612FNG |
| 28BYJ-48 geared stepper | ULN2003 (comes with the motor) |