This LED calculator will help you design your LED array and choose the best current limiting resistors values. To get started, input the required fields and hit "Design Circuit." Does the math for you, will output either a wiring diagram or schematic. Useful because it gives you defaults to start playing around with (who knows how many mA an LED draws off the top of their head? even I don't.)
Repair info and schematics for mostly older MFM hard drives. The maintainer is getting their hands on as many ancient drives as possible and reverse engineering the circuitry, not only so people will (hopefully) be able to repair them, but possibly so that replacements can be manufactured.
To help people who want to repair their vintage IBM EGA cards, I've put together this reference schematic and layout. The schematic is closely modeled after the schematic in the IBM technical reference material but with mistakes corrected and more information added. The PCB layout is closely matched to the original card. Using KiCad, you can click on a component on the schematic and it will automatically highlight it in the layout, so it's perfect if you need to probe pins with a scope, logic analyzer, or even just a multimeter.
You might be excited about fabricating this board so you can have your very own clone of the EGA card, but unless you have the full set of custom chips, the board will be useless.
I've reverse engineered the power board from a Thinkpad 700C. The P/N is 35G4785, and the FRU number is 48G3712. A very similar or identical board is also present in the Thinkpad 700. The schematic isn't perfect. Open a bug report if you find a mistake. Not all components were identified. A number of parts did not have designators on the silkscreen, so I assigned them new ones starting at 300.
The circuit board has four layers and an aluminum core, presumably for heat dissipation.
Do not fabricate this design. The PCB layout is for reference only. There are ground plane cuts in layer User.9 that need to get transferred to the ground plane. There are minor footprint differences as well. There are still unidentified components in the bill of materials.
The Amazing All-Band Receiver is basically a diode detector followed by a high-gain audio amplifier. This is not a multi-band receiver; it picks up everything at once! The detector uses a biased Schottky diode for excellent sensitivity and bandwidth; the detector will detect signals from below the AM broadcast band up to the microwave bands. The number of interesting signals is surprising; it is fun to drive around listening to the numerous strange sounds.
By trying different antennas and locations, this receiver has picked up AM radio stations, FM stations, TV video (buzz), car lock transmitters, cell phones, and even the microwave oven (a whoosh-whoosh sound as the microwave spreader rotated). It isn't clear how FM stations are demodulated; perhaps the antenna Q is sufficient for slope detection. (See reader Karen's excellent theory.) Even the familiar buzz from a narrow-band FM pager transmitter has been heard - somehow. There are some mysterious signals out there, too! What is that occasional descending whistle over by the highway? Some vehicles emit a curious buzz, too. If you hear a mysterious click-click now and then, its your cell phone! Don't expect to tune in international shortwave stations. This receiver is for strong, local sources. The advanced experimenter will find it useful as a detector section for low power tuned receivers.
The RFBitBanger is an off-the-grid QRP radio. It is not just designed to be used off the grid, it is designed to be assembled and maintained off-the-grid. Most radios require specialized parts that would be difficult to obtain in an extreme parts shortage or in remote places. This radio is designed to be assembled and maintained using the most common jellybean components that might be in a hobbyist junkpile. It will mainly support low bandwidth/digital modes to make the most of limited power.
This is a single band double-sideband radio, with the band changed by pluggable external filters on 20 m to 80 m. A double-balanced ring mixer is used to provide good rejection of strong stations while not requiring any custom ICs such as SA612 or FST3253. The mixer has strong drive to reduce nonlinearity. The radio is made from readily available through-hole parts which are widely available and have multiple vendor alternatives. The parts needed are very common so that cheap spare parts can be stockpiled or scrounged from other equipment so that the radio may be more easily maintained in off-grid conditions. The includes ATMEGA328P/Arduino Nano, LM358 op-amp, LM386 audio amplifier, 2N7000 MOSFETs, 2N3904 NPN transistor, SS8550 PNP transistor, and a HD44780 display. It can use a SI5351A frequency synthesizer IC soldered to the board, or a plug-in SI5351A development module. There is a MS5351 workalike for this IC as well. Ferrite cores are needed for transformers/chokes which can be easily bought (FT50-43) or scrounged as EMI suppression beads from cables.
CatSniffer is an original multiprotocol and multiband board made for sniffing and communicating with IoT (Internet of Things) devices. It was designed as a highly portable USB stick that integrates the new generation of the chips TI CC1352, Semtech SX1262, and Microchip SAMD21E17.
This board is an auditing tool for security researchers looking into IoT security. The board can be used with different types of software including third-party sniffers such as SmartRF Packet Sniffer, Sniffle, zigbee2mqtt, Z-Stack-firmware, our custom firmware, or you can even write your own firmware for your hacking needs.
It can also be (pre-)ordered here: https://electroniccats.com/store/catsniffer/
Kit Space (formerly called Kitnic) is a registry of open hardware electronics projects that are ready for you to order and build. It could be described as a "Thingiverse for electronics". Click on any project to get further info, download the Gerbers and see the bill of materials.
Click once, order everything.
A 100% compatible replica of the famed SB 1.0 sound card. 8-bit ISA card. Full bill of parts. Even has a hex dump which turns an Atmel 89S51 into an 80C51 DSP chip (if you don't feel like buying one from China).
CC-BY-SA v4.0.
A wiki of designs, schematics, and links to open source electronics projects. If you get lost in here long enough you'll find some interesting stuff.
A suite of open source electronic design tools. Uses a GUI for schematic capture. Also capable of analog and digital simulation, generation of parts lists and export of PCB designs for fabrication.
A lot of manufacturers leave their schematics on the FCC's website.