Siemens G120C Drive
Hardwiring a drive allows for local control using physical switches and potentiometers.
This configuration is common in standalone systems and serves as a reliable backup to networked control.
Wiring Digital and Analog Signals
The G120C uses specific terminals for different signal types:
Digital Inputs (DI): Terminals 5 and 6 are used for On/Off and Reversing. These require a 24V signal sourced from Terminal 9.
Analog Input (AI): A potentiometer uses a 10V reference (Terminal 1), a ground (Terminal 2), and a wiper/input (Terminal 3). It is critical to land the wiper on the center terminal to prevent short circuits.
Analog Output (AO): Terminals 12 and 13 provide a milliamp signal to drive an external speed meter.
Troubleshooting the Common Reference
A frequent mistake in hardwiring is neglecting the digital common. For the inputs to trigger, Terminal 28 (0V) must be bridged to the common terminals (such as 69 and 64). Without this reference, the drive cannot complete the circuit to "see" the 24V signals from your switches.
Macro 12 Configuration
To tell the drive to look at the physical terminals instead of the keypad, you must select the correct Macro:
1. Navigate to Setup > Advanced Setup.
2. Select IO Setup and choose Macro 12.
3. Save the settings to the drive's memory.
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