What is it?

The Protean 8x2 is an Arduino compatible development board with power control in mind. It gives you the freedom to use the FETs, (essentially DC power switches), and connectors you want. You can determine the full turn-on voltage most efficient for your FETs, (the Vgs), without hunting for “logic-level” FETs. Because it has a place for optocouplers to provide electrical isolation, you don’t need to worry that it will fry the ATmega328P micro-controller. Easy to follow wiring guides are also now available.

These boards are being sold nearly at cost since the Kickstarter was not funded.

Why did you make it?

I love the idea of node based controllers seen in modern pinball machines, but nearly all of them are proprietary and virtually undocumented! The hardware available for custom machines run about ~$100+ per board, are generally large (~20 sq in./~130 sq cm), require a separate main controller, and have a fixed serial protocol and rate. Other boards were understandably meant for use in existing, typically older machines, and were more expensive.

From the “build your own” perspective, there were numerous Audrino FET shields to chose form, (and relay boards), but all with different specs, hardware interfaces/terminals, and limited FETs. Of course they also required a separate Arduino or controller board.

Many people just use an Arduino Mega and run wires to multiple different modules and components. The same could be done with the awesome Teensy 3.5/3.6, (an ideal main controller for pinball in my opinion). But the otherwise tedious point-to-point or expanded board-to-board method didn’t seem very appealing, easily scalable, or space conscious. There’s already enough unavoidable connections to be made.

What makes it special?

• One-third smaller than existing boards with 16 channels
• Down to half or less overall cost even considering needed additional components
• N and P channel MOSFET support
• Simultaneous input and output handling capability
• Built-in RS485 interface
• Fully customizable interface protocols or standalone functions
• Wide power connector support
• A place for back-EMF/flyback protection diodes

What are the specifications?

Technical:

• Controlled by the ATmega328P, the classic Arduino chip (which includes TWI/I²C and SPI interfaces)
• RS485 interface chip (data direction controlled by pin D2; tested up to 2M baud)
• Recommended logic supply: 3.3V to 5V
• Output/High voltage side designed to work up to 100 volts, (and has been tested with ~120V pulsed DC)
• 16 optically isolated channels (main I/Os).
• Up to 3.67 amps on a single channel with bare PCB trace
• Up to 7 amps on FET source common with bare PCB trace
• Power traces bare, allowing for added solder to increase current handling.
• LED indicator for logic power
• LED on port D3, (or digital pin 3).

Component Footprints Ready:

A place for...

• TO-220 case FETs
• 4-pin DIP or gull wing SMT optocouplers
• LED (3mm) and resistor for main power indicator, (both upper 8 and lower 8 channels)
• 5mm x 20mm fuse holder or capacitor, (both upper 8 and lower 8 channels)
• Vgs, or gate-to-source voltage select resistors, surface-mount or through-hole, (both upper 8 and lower 8 channels)
• Back-EMF/flyback protection diodes, (surface-mount on top or through-hole on bottom)
• Optional lower value gate discharge resistors, surface-mount or through-hole, (100k already included)
• An LD1117S regulator in an SOT-223 package for POE on spares configuration, (on bottom of board)
• TVS diodes in an SOT-23 package for ESD protection on power, RS485 lines, TWI/I²C lines, port D3, and the 16 I/O header pins, (all on bottom of board)

Connectors Supported:

• Main power connector pitches: 3.5mm/~3.8mm, 0.156" (3.96 mm), and 0.2" (5.08 mm)
• Main power connector alternatives: 0.2" pitch PCB mount quick connect terminals (would straddle two channel lines if used as output)
• Logic power connector pitches: 0.1" (2.54 mm), 3.5mm/~3.8mm, and 0.156" (3.96 mm)
• Vgs connector pitches (as part of main power connectors): 3.5mm/~3.8mm and 0.156" (3.96 mm)

Mechanical:

• Board Dimensions: 2.7" x 4.6" (68.6mm x 116.8mm), the size of two Arduino Unos
• Mounting Hole Centers: 2.4" x 4.3" (~61mm x 109.2mm)

What’s included?

• One Protean 8x2 board ready for configuration

No connectors, fuse holders, optocouplers, or FETs are included since these things are dependent on your application.

This board was assembled with lead-free solder, however, there may still be trace amounts of lead present, so for the sake of satisfying absurd and harmful regulations...

WARNING: This product can expose you to chemicals including lead, which is known to the State of California to cause cancer, birth defects, or other reproductive harm. For more information, go to www.P65Warnings.ca.gov.