From Prototype to Production: PWM Generator & Servo Driver for Non-PWM PLC

In many industrial systems, not all PLC models provide native PWM output. When PWM expansion modules are available, they are often expensive and unnecessary for simple positioning tasks.

I needed to control a low-voltage servo (MG996R, 5–6V) using a standard 24V PLC digital output. Since the PLC did not support PWM, I decided to design a dedicated PWM Generator & Servo Driver board as a cost-effective solution.

Prototype Phase

The first version was built using a perforated prototype PCB.

The goal was to validate:

• 12V/24V PLC signal compatibility
• Servo movement stability

After several adjustments, the prototype worked reliably. The servo response was smooth and consistent under normal load conditions. Once the concept was proven, I decided to redesign the circuit into a proper PCB.

PCB Design & Fabrication

The circuit was redesigned into a 2-layer PCB for:

• Cleaner routing
• Better power distribution
• Reduced noise
• More professional mechanical structure

The PCB was fabricated using JLCPCB. The board quality was excellent, with accurate drilling, clean copper traces, and clear silkscreen. The compact layout also improved reliability compared to the prototype version.

Small Batch Production

After testing the first PCB batch, I proceeded with small-scale production of 30 units. These boards were used for real application testing and market validation.

The system successfully enables standard PLC digital outputs (12V/24V) to control low-voltage servo motors without needing an expensive PLC PWM module.

Technical Overview

System flow:

PLC 12V/24V Digital Output

→ Signal Conditioning

→ PWM Generator

→ 5–6V Servo Driver

→ MG996R Servo

Main features:

• 12V/24V PLC compatible input
• Stable 50Hz servo PWM
• 1–2ms adjustable pulse width
• Compact 2-layer PCB

This project started from a simple prototype on a perforated board and evolved into a small production run using JLCPCB.

It demonstrates how custom PCB design can provide a practical and economical solution for PLC systems without built-in PWM functionality.

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