Shared Projects

High performance multi-output linear power supply.

Nordic Semiconductor’s low-power 2.4 GHz RF radio with pcb antenna and matching circuit per Nordic’s spec. Using much smaller XRCHA16M Murata crystal to reduce cost and board size. Improved layout and ground pattern slightly, corrected silkscreen error.

PIC18F2455

microSD card via PIC24F to ethernet

Same overall functionality as the 1st version, but with a pin fix and less connections to the FPGA.

WARNING I forgot a resistor between the Pi and the base of Q1. You can still use this board if you’re willing to do a little hackery (put a 1k between the Pi and the base of Q1), or if you only want the filter section. I suspect I’ll re-release a fixed version of this at some point.

A digital amplifier for GPIO4 on a Raspberry Pi, followed by a 7 pole low pass filter to clean up the signal. I don’t know if the amp will work, these are my prototype boards to test. The idea is to treat GPIO4 as a DIGITAL signal, amplify accordingly, then filter when done. I honestly have no idea whether this will work. Worst case, leave off Q1-Q3, R1-R3, and jumper from the input at Q1 to the output at Q3 or Q2 and just use the filter section of the board. Your RF neighbors will be glad you did.

I modeled this amp after a CMOS logic gate: complimentary gates always either off or in saturation, and only dissipating heat during the transition. Faster transistors (than 2N3904/6) will hopefully be more efficient. GPIO4 is a 3.3v signal, but the 3.3v supply can only give 50mA. To use the 5v supply and be able to turn Q3 off, I first needed to amplify the 3.3v signal from GPIO4 to a 5v signal, which is what Q1 does. I’m honestly not sure whether the 470ohm R1 will pull Q3 out of saturation quick enough, so we’ll see how that goes.

This can be used on any band, but the values below were calculated for a -3db point of 150MHz for use on the 2m Ham Bands. Combine with something like WsprryPi or nbfm (proper download link) and you’ve got something potentially really useful.

Parts:

• C1: .01uF
• C2, C5: 9.1pF
• C3, C4: 39pF
• C6: 680uF
• C7: 10uF (I had these laying around, so I didn’t order them and therefore don’t have a link handy.)
• L1, L3: 64nH
• L2: 100nH
• R1: 470
• R2, R3: 1k
• R4: 10k
• SMA Connector
• Q1, Q2: 2N3904, or similar NPN BJT. (I also had these laying around so don’t have links for you) You might want to go with something better for RF.
• Q3: 2N3906, or whatever the PNP counterpart is to whatever you go with for Q1 and Q2.

Disclaimer: I list components here for a low pass cut-off of 150MHz for use on the 2m ham bands. Using these values for lower bands (ahem 3m, FM broadcast) will work, but you won’t be filtering nearly as well and will still be putting out gobs and gobs of harmonic noise and probably pissing off other legitimate users, ESPECIALLY if you are using the amplifier here. You’ll attract a lot less attention by re-calculating the values of C2-C5 and L1-L3 for a cut-off of about 110MHz (or lower, if you know you’ll be using the lower part of the band.) To be clear: transmitting on the FM broadcast band without a license is illegal (at least here in the US), but if you’re going to use my board to do it, I’d rather you do it cleanly.

pickit3 to rj12 adapter

Recommended right angle header: Digi-Key 3M9471-ND

Recommended vertical RJ12 connector: Digi-Key WM3789CT-ND

Controls a “standard” LCD over I2C.

Designed to be attached to the back of the LCD, either monochrome or RGB, component side /facing/ the back of the LCD. This leaves the back almost entirely bare, so less worry about shorts and whatnot when mounting. (I should make a version that uses SMT connectors to the LCD.)

Attiny84-based, with AVR ISP broken out as a non-standard 6-pin connector. The layout was choosen to take advantage of the fact that SPI and I2C use the same pins on Attiny84’s, meaning only one connector is needed for both programming and field use.

For more schematics, non-working firmware, and potentially help, see the github repo.

Courtesy TI PMP-9531

ForkinBrain - 18 Channel Xmega model

Temperature transmitter with 12f683 and 3 DS18B20 sensors. Includes programming header

Power Distribution Board for Scoregasm

A quick and dirty breakout board for testing the MAX16820 buck IC.

• 0805 components
• See datasheet for all other needed information.

parallax propeller and serial communication

Constant current,constant voltage lab power supply featuing the LT3080

Breakout board with two independently addressable ST Microelectronics' 2 Mbit (256 kbyte) M24M02-DRC I2C EEPROMs designed to be mounted onto the Teensy 3.1 and use digitalWrite for power and ground due to the very low-power (< 2 mA per EEPROM) requirements. Can also be used as a traditional breakout board since VIN ranges from 1.8 to 5.5 V. Cutting one or both traces between the solder jumpers enables write protect mode allowing access to the data already written but disallowing further write operations. The write protect is reversible by simply soldering the junction again. Operating temperature range is -40 C to +85 C making this an ideal solution for portable/remote data logging when power and space are at a premium. EEPROM write operational for 4 million write cycles and data is retained for 200 years! Minimized width to make it even more appallingly small!

ST Microelectronic’s ultra-low-power real time clock coupled with Measurement Specialties MS5637 pressure and temperature sensor and ST’s M24512DFM EEPROM in an appallingly small add-on board for Teensy 3.1. Power is supplied via digital write to general GPIO pins since the total power requirement never exceeds 2 mA. Communication is via I2C and there are 4K7 pullup resistors on board. The temperature sensor allows the Teensy 3.1 microcontroller to make periodic calibration updates to the RTC calibration register so the clock remains temperature compensated for maximum (~2 ppm or 1 minute a year) accuracy. The clock outputs the usual date, days, hours, minutes, etc. but also outputs tenths of seconds as well as hundredths of a second.The on-board EEPROM is useful for data logging and storing alarm patterns (music) for output to a small speaker. With 512 kbits (64 kBytes), lots of data can be logged and dozens of alarm sounds can be stored; one for every occasion! Added Taiyo Yuden PAS3225 2.6V 14 mF super capacitor and 1N4148 diode to provide power to the RTC time keeper even when disconnected from the microcontroller. The PAS3225 5 microAhour super cap can run the RTC (which needs ~330 nA at 2.6 V) for about 15 hours.