diy

Gremblnote Application Note GN-0001: OTA-based Automatic Gain Control (AGC) Circuit

Schematic diagram for Automatic Gain Control (AGC) circuit)

I developed this automatic gain control (AGC) circuit to compensate for the -3 dB gain after each filter stage in a 2-stage, 4-pole voltage-controlled filter (VCF). I’m posting this because it was surprisingly difficult (rather, impossible) to find a low-distortion operational transconductance amplifier (OTA) driven AGC schematic I could use directly.

Precision current reference

A precision current source like you’d find in an SMU would be a very helpful tool for some of my other projects. But an SMU costs an arm and a leg… my needs were not so great. Could I make what I needed without breaking the bank?

3-D printed case for Raspberry Pi & LCD

A 3-D model of a case for a Raspberry Pi and LCD screen (not shown)

I recently designed a custom case to fit a Raspberry Pi 4 and a 7″ LCD screen. I wanted a small tablet-like computer I could set up to look at while seated at a table, or standing at a counter in the kitchen.

Building an embedded device for sailboat racing: power and packaging

A polycarbonate plastic enclosure for the device, with an internal aluminum PCB-mounting board

With the software running on the Raspberry Pi and touchscreen in a “bench test” format on top of my desk, it was time to start thinking about how I would actually package this up into a complete device that I could install on the boat. It needed to be waterproof, powered by the boat’s battery bank, and ideally no larger than necessary.