Glenden Crunch's Clever Controller Gets a Pair of Aglient/Keysight Attenuators Back Up and Running
No controller? No problem: roll your own, with a Microchip ATmega328-AU microcontroller at its heart.
Pseudonymous maker "Glenden Crunch" found a pair of Agilent/Keysight attenuators in storage, but without the necessary control unit to make them work — so set about designing one, in a natty 3D-printed housing.
"It so happened that we got two attenuators," Crunch explains, "[an] Agilent 8494H and 8496H. They were lying idle for a long time, because there was no control controller. Of course, four simple switches would cope with this task, but I wanted an implementation with a display showing the current attenuation value and software control. The project was made in Altium Designer and Atmel Studio."
The attentuators in question are devices designed to allow a signal with a frequency from zero Hertz up to 18GHz to be reduced in strength in 1dB steps — from 1-11dB for the 8494H and up to 110dB for the 8496H. The chosen reduction is programmed into each unit from a control box, which is what Crunch's board replaces.
The custom PCB is built around a Microchip ATmega328-AU microcontroller, a WCH CH340G serial chip, a DC-DC step-up booster, a SN74HC259 latch, and Darlington ULN2803 transistors. A rotary encoder on the front allows the user to pick from the available attenuation values, which are displayed on a compact display at the front of the housing.
"Since the device is used to automate measurements," Crunch adds, "it has software control via a virtual COM port." Provided over a USB connection, this works with Agilent/Keysight's existing desktop software, sending AT-format commands and receiving their responses.
The project is documented in full on Instructables, while design files are available on GitHub along with firmware source code and a 3D-printable case.
