Shared Projects

Mussel heart rate module RevB - for MAX30101 or MAX30102 pulse oximeter sensors, used for measuring heart rate through the shell.

The little board used to hold the Hall effect sensor chip and attach the data cable that goes to the separate data logger. This part gets encased in heat shrink and then glued to the shell of the critter. One of these is needed per animal. The footprint is designed for an Allegro A1395 (or A1393 or A1391) Hall effect sensor chip, along with a 10k ohm resistor and 0.1uF capacitor, both in 0603 size.

RF power amplifier

Low cost LS/FS/HS USB sniffer with Wireshark interface

SlimStack32 adapter for the Herder

Easy fix for a failing rotary encoder at this link. The price is for three (3) PCB’s because OSHPark only sells a minimum of three per order. Ships anywhere in the USA for FREE. Shipping is also FREE outside of the USA but some countries might charge hefty customs and handling fees.

Digital re-creation of an analog VFO. See www.w9ac.com for details. B.O.M. below:

QTY DESCRIPTION

(1) ESP32 Board https://www.amazon.com/dp/B0811LGWY2?psc=1&ref=ppx_yo2ov_dt_b_product_details There are MANY ESP32 variations so stick to this one.

(1) 1 .8-inch TFT Display https://www.ebay.com/itm/224237573577

(1) Si5351 PLL Board

(1) Encoder w/ Switch (Bourns PEC11R-4020K-S0024)

(1) L4940V5 LDO 5.0V Linear Regulator

(2) 2K2 1/4W Resistors

(1) 68R 1/4W Resistor

(1) 180R 1/4W Resistor

(1) 0.33 uF Film Cap 0.1” Lead Spacing

(1) 0.1 uF Film Cap 0.1” Lead Spacing

(1) 1N400x Diode

(3) N.O. SPST pushbutton panel switch

(1) Molex 0026604030 3-Pin Power Header (DigiKey P/N WM4621-ND)

(1) Optional 2 .1 mm coaxial DC Jack (Schurter 4840-2211)

Also required: Standard 0.1-inch breakaway headers and sockets.

A minimal Linux single-board-computer design using an STM32MP151 SoM (MYiR Tech). Build details, schematic, BoM, and KiCad files are available on GitHub.

PIN Diode-based beta, gamma radiation particle counter with differential sensing, Version 2

This is a beta/gamma particle detector designed with differential sensing of the PIN diode signal, to establish some rejection of common-mode EMI. Transimpedance amplifiers with high gain are very similar to an oscilloscope probe amplifier: high impedance and very sensitive to external interference. By sensing symmetrically across both sides of the diodes, common-mode rejection of 40dB can be achieved. In batches of 1% resistor and 5% capacitor tolerances, matching can be achieved of 0.1% for R and 1% for C. This will yield 40dB CMRR.

This design is intended for remote sensing for balloon flights or similar weight-sensitive applications: PCB weight (0.4mm material) is 0.75g. As such, the added weight (and difficulty) of shielding is avoided, or reduced, by incorporating common-mode rejection.

Specific changes from Version 1 (“PrtCntGerber” project on Oshpark): Board size reduced by 0.2" in X and Y dimensions. Added board clearance margin to make application of diode light blocking material (such as black electrical tape) easier. Extended backside ground plane underneath the sensor diodes, significantly improving CMRR and EMI rejection. Added backside pads for additional sensor diodes (see notes). Event detection threshold now referred to a bandgap voltage reference. Front-end U1 opamp now MAX4489 (higher GBW, low noise). U2,3 now OPA2325 (10 MHz GBW, low offset). Threshold voltage reduced to detect lower energy events.

Notes: The V1 board accommodated 6 PIN sensor diodes. V2 now adds the capacity to add up to six more on the back side of the board. But there is a tradeoff: Photodiode transimpedance amplifiers exhibit voltage noise peaking proportional to (C_diode / C_integrator). With the V2 improved CMRR and the lower noise of U1, I was able to lower the comparator event threshold from 350mV to 200mV (increased sensitivity), while maintaining margin over noise, with 6 diodes. As the number of diodes increases, the TIA amp noise peaking increases, so that the threshold would need to be increased (sensitivity reduced) so that the detector doesn’t trigger on noise. The component settings for the comparator (200mV) are good for 6 diodes. 225-250mV should be good for up to 8-9 diodes. I do not recommend going past 9 diodes - there would be no benefit due to reduced sensitivity.

Do not exceed 5.5V Vcc.

Small footprint Si5351a-based transmitter with TCXO reference, intended for flight / telemetry

Github link with schematic, pictorial, BOM, gerber and photos: https://github.com/stefanoaz/BeaconTXv1a

This transmitter was designed to be a replacement for existing Si5351a based synthesizer breakout boards, for applications requiring small size, light weight and TCXO reference frequency stability. For flight telemetry from a superpressure balloon, the board also incorporates static bleed resistors on the Clk0 and Clk1 outputs, which are intended to drive a dipole.

This module is a drop-in replacement for the synthesizer board used by Ken Daniel for his airborne beacon described here: https://github.com/kenndaniel/K9YO_WSPR Benefits are that it saves about 2 grams of weight vs the Adafruit synth, and is more temperature stable.

General purpose shield for WEMOS D1 mini with I2C and output to a FET. Could be used to drive lights, heater, fan, using I2C input of temperature & humidity. Work in progress.

The ItsyBitsy M4 Charger Backpack is an Adafruit ItsyBitsy M4 Express-compatible piggyback module that converts the 3-sided pinout of the ItsyBitsy to dual in-line for use on typical solderless breadboards and soldered protoboards. The adapter was also designed with extra solderable pin connections.

Included is a STEMMA-QT connector that can be optionally configured via solder jumpers to connect to the ItsyBitsy’s UART (RX/TX) or I2C (SCL/SDA) signals. A 2-pin JST LiPo battery connection is on-board that supports charging (100mA charge rate), compatible with Adafruit’s standard battery connector polarity.

6 channel NMOSFET driver

A piggybottom LiPo charger board for attaching underneath an Adafruit ItsyBitsy NRF board. A 2-pin JST LiPo battery connection is on-board that supports charging (100mA charge rate), compatible with Adafruit’s standard battery connector polarity.