Introduction

The stepper motor controller is normally used in achieving accurate sets through digital control. Additionally, it changes a consecutive entry of pulses to an accurately defined increase on the mechanical shaft set, a point where every pulse shifts the shaft on a constant angle. Mostly, the stepper motor’s set is guided or controlled to shift and constantly stop in one of the steps that lack a feedback sensor: an open loop stepper motor control. Therefore, a stepper motor control offers consecutive entries of pulses to control the motor, which shifts to the required set and speed.

Components of a Stepper Motor Control Circuit 

To design a stepper motor control circuit, you need the following vital components:

• A controller
• Driver
• Power supply unit
• Heat sink
• Switches
• Connecting wires

KiCAD Schematic Components

1. C1 1 470uF C_Polarized_Small_US Capacitor_THT:CP_Radial_D4.0mm_P2.00mm Polarized capacitor, small US symbol
2. C2, C3 2 0.01uF C_Small Capacitor_THT:C_Disc_D3.4mm_W2.1mm_P2.50mm Unpolarized capacitor, small symbol
3. D1, D2, D3, D4 4 1N4007 1N4007 Diode_THT:D_DO-41_SOD81_P10.16mm_Horizontal 1000V 1A General Purpose Rectifier Diode, DO-41
4. J1 1 12V Bat. Conn_01x02 Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Horizontal Generic connector, single row, 01x02, script generated (kicad-library-utils/schlib/autogen/connector/)
5. J2 1 VCC Conn_01x02 Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Vertical Generic connector, single row, 01x02, script generated (kicad-library-utils/schlib/autogen/connector/)
6. J3 1 Control Logic Conn_01x02 Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Vertical Generic connector, single row, 01x02, script generated (kicad-library-utils/schlib/autogen/connector/)
7. L1, L2, L3, L4 4 L_Small L_Small HCTI-220-5.8:IND_HCTI-220-5.8 Inductor, small symbol
8. Q1, Q2, Q3, Q4 4 BC548 BC548 Package_TO_SOT_THT:TO-92_Inline 0.1A Ic, 30V Vce, Small Signal NPN Transistor, TO-92
9. R1, R2, R3, R4 4 1k R_Small Resistor_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P5.08mm_Horizontal Resistor, small symbol
10. U1, U4 2 7404 7404 Package_TO_SOT_SMD:SOT-343_SC-70-4_Handsoldering
11. U2 1 7486 7486 Package_TO_SOT_SMD:SOT-343_SC-70-4_Handsoldering
12. U3 1 L7805 L7805 Package_TO_SOT_SMD:ATPAK-2 Positive 1.5A 35V Linear Regulator, Fixed Output 5V, TO-220/TO-263/TO-252

Building a Stepper Motor Control Circuit

When constructing a drive for a stepper motor, the initial consideration is the choice of the controller. Opt for a model with at least four output pins, encompassing features like a serial port, ADC, and timers. Stepper motor controllers are predominantly divided into two categories: open loop and closed loop. The open-loop option is uncomplicated and more cost-effective than closed-loop systems. In numerous motor applications, the open loop controller performs effectively.

KiCAD Schematic Diagram

How the Circuit Works

 Utilizing four BC548 transistors, the driver circuit operates the motor windings. Decoding the two-bit control logic to manage the motor's four windings involves two NOT gates and an XOR gate. Diodes D1 to D4 safeguard transistors from transients during winding switching. The control logic d0 and d1 dictate rotation direction and speed. Below is a circuit diagram of a basic stepper motor controller or control circuit designed with elementary parts.

Pin Configuration

The circuit's control logic originates from a 2-bit up/down counter driven by a 555 astable multivibrator. The count direction determines the rotation direction, while the multivibrator's frequency influences speed. In the provided diagram, IC1a and IC1b belong to the same IC 7404. Connect pins 14 and 7 of IC1 and IC2 to +5 V and ground, respectively, though not displayed. For 5V, utilize a 7805-based power supply circuit. The required voltage for the stepper motor (Vcc) varies; here, up to 24V stepper motors can be used. Substitute BC548 transistors with higher-power alternatives like 2N3055 for greater voltage and power.

How the Current Works in a Stepper Motor Control

Stepper motors are controlled using constant voltage drives that apply a continuous positive or negative voltage to each winding for motion. Yet, the winding current, not voltage, imparts torque. Current (I) is linked to applied voltage (V) through winding inductance (L) and resistance (R). Such drives are termed L/R drives. Achieving high torque at high speeds necessitates a sizable voltage with low resistance and inductance. With L/R drives, boosting voltage for a low-voltage motor involves an extra resistor per winding. However, this approach loses power, generates heat, and is considered suboptimal.

Quote and Order

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