Shared Projects

Small Bipolar Stepper Driver

v1.3 of the board - tested to work! See documentation, firmware, BOM on my github page:

https://github.com/pimvanpelt/esp8266-ups

SEGA MASTER SISTEM CARD 512K + SRAM + PIC MAPPER

VERSION 1 NOTES:

• Trimpots should be 1M not 25K.

• Issue (minor): The trimpot midpoint pins are at the top rather than in the middle of the three as they should have been. This comes from selecting the wrong Eagle package! You can instead solder a header here and wire it to an external pot, or use a trimmer with long leads, put some wire insulation around the center lead and bend this and an end lead to cross each other to fit into the proper holes.

• This is not a high frequency board. It’s not meant for signals above say 100 kHz (and you will be hard pressed to get the PyBoard to do anything useful with signals any faster than that).

• The input impedance is approximately the parallel resistance of the top and bottom parts of the trim pot, so if you adjust the input signal attenuation, you adjust the input impedance. (See revision list for Version 2). The board is meant to be used with an external noninverting buffer stage before the input if input impedance is critical.

• This board does not provide level translation, so as-is only unipolar input signals (can be adjusted for up to 0 - 10 V) will be detected. It is relatively safe to apply signals that are too big because the MCP6002 will merely clip them to the 0-3.3V range of the PyBoard.

Bipolar signal input hack

You can “hack” it to allow bipolar input signals by soldering two 100k resistors between 0 and +5V rails as a voltage divider, then wiring the center of the divider to the non inverting input pins of the MCP6002 op amp socket. This will of course affect input impedance.

REVISION LIST FOR VERSION 2:

These are changes to be implemented on a future version.

• Add noninverting buffer stage to inputs with constant, designed 1Mohm input impedance.

• Add level translation for inputs to allow bipolar signals.

• Add inductive filter on 5V rail to reduce digital noise from the PyBoard (esp. when supplied from USB)

• Change trimpot pins so trimpot center tap is the center pin

• Add spot for optional output AC coupling capacitor to eliminate the DC bias of PyBoard DAC.

What is this?

Op-amp buffered/scaled input & output to/from PyBoard via BNC connectors. This circuit is nothing fancy and version 1 is probably not even a very good design.

MCP6002 provides attenuation to allow input voltages up to 0-10 V (unipolar only). These will be scaled (and clipped if necessary) to the 0-3.3V range of the PyBoard. See Version 1 Notes.

To omit input scaling and have very high input impedance (equal to that of the MCP6002 datasheet) you can simply bridge the trimpot center terminal to the top terminal. Maximum signal will be 0 to 3.3V in this case. Note that no voltage translation is provided.

MCP6002 is powered on 3V3 rail and will clip any signal excursions beyond 3.3V or below 0. This is very convenient because PyBoard inputs are not well protected.

TL072 provides non-inverted buffered output signal of DAC on pin X5. Requires external bipolar supply to be plugged onto the board (viz, 2 9V batteries connected with a common center). You can set the scaling of the output voltage by suitable selection of scaling resistor. Recommend using a socket for this resistor so you can change it as needed. Note that the -12V rail IS strictly necessary – even if your output signal is only positive.

PyBoard will be plugged onto 16 pin female header. Recommend on PyBoard itself to solder on extended-pin length female headers (available e.g. Adafruit) so that you can make connections with other PyBoard pins on the PyBoard itself as well as being able to plug it onto this in/out board.

All fixed resistors are 10K 1% or 0.1%

Micro B USB connector adapter.

Intelligent Power switch with attiny85 for brains.

T1-SI2301CDS R1-100ohm C1-10uf C2-100uf D1-WS2812B U1-attiny85 [email protected]

code TBD

Currently untested, order with care!!!

This board allows you to connect the common (chinese) CC1101 868MHz modules to the SPI of the Raspberry Pi

A Raspberry Pi Zero handheld retro console. https://hackaday.io/project/25256-ye-olde-nowt

rightside

67firebird LED board

Simple breakout for the SM9543 differential pressure sensor.

I made this tiny board to use as an interface between an Orange Pi Plus (which can get quite hot) and a little fan. I’m also using as large a heatsink I could find & fit into the available space, which nicely also makes contact with the RAM chips.

The circuit I used is here.

The parts listed below I got form DigiKey, except for the RPi header socket, which also came from Amazon (as I neglected to include it in the DigiKey order). The best fit I could find on Amazon is an 18-pin stackable header socket.

• Q1: Infineon IRLML2502GTRPBF
• D1: Panasonic DB3X209K0L
• R1: Vishay Dale CRCW1206100KJNEA
• J2: JST B2B-XH-AM(LF)(SN)

GitHub repo

See https://github.com/urjaman/pnd-ser-6pin

Tapuino Normal Sized Board

2532 to 2732 socket board

Allows a 27C512 to be used as a PLA replacement in a C64. C1 is 68 pF

C64 Tape Emulator Tapuino