Controller for the hp8496G attenuator

OH2NLT 29.9.2011




I managed to get hp8496G high performance 110dB attenuator. Unfortunatelly no controller and the control connector were also broken. I decided to make my own simple controller for the attenuator. Attenuator operates with four bistable relays or solenoids. Nominal voltage for the solenoids is 24VDC. After some measurements I decided to power the controller and attenuator from three 9V batteries. 27V is more than nominal voltage but it does not matter because solenoids are powered only for state transition which is few milliseconds.

Controller board contains 3-digit LCD display, two buttons, relay driver and small MCU. The user interface is simple. Only two buttons and the attenuator setting are shown with the LCD display.

Broken control connector

Control connector removed

Connections to the controller PCB

Schematic diagram of the controller

MCU program & source code

Picture of the controller board

MCU program development

Testing & performance measurements