Driver Boards

How do the Driver Boards work?

The boards are chained together using a 2-wire serial bus (RS-485).  A master board gets data from the P-ROC and sends it out on the serial bus to all of the other driver boards.  The address on each driver board is set via dipswitches, and each board monitors the bus until it sees data destined for its address.

The logic circuits run on 5V DC, and the power circuits (not available on PD-LED) run on 5V-80V DC or 5V-20V DC, depending on the type of Driver Board.


How does a Power Driver Master or Master Combo Board connect to the P-ROC?

A 16-conductor ribbon cable (included with the purchase of a Power Driver Master or Master Combo) plugs onto P-ROC J34 and Driver Board J8.


Can I use any RS-485 transmitter as a Master, or do I have to use a master?

Any RS-485 transmitter device can be used to master your chain of boards as long as its data logic input is compatible with the P-ROC's 3.3V CMOS output, and as long as it can transmit data at 12 mbps or higher.

Note that any of our driver boards can be purchased with integrated master logic (master combo boards).  If at least one of your boards will be located near the P-ROC (or whatever controller you're using), then you might prefer to order that one as a master combo.


What additional hardware do I need to use a driver board?

A P-ROC, 5V DC power supply, additional DC power supplies for the transistor banks (5V-80V) depending on your needs, and whatever devices you want to control with the board.


Can you show me how I can use a Power Driver 16 board to control coils and flashlamps?


Can you show me how I can use a Power Driver Matrix 8x8 board to control a lamp matrix?



What voltages do the transistor banks support?

Power Driver 16:     Bank A and Bank B: 5-80V DC

Power Driver Matrix 8x8     Bank A (Source Bank): 5-20V DC, Bank B (Sink Bank): 5-80V DC


What is this 'sink' and 'source' stuff you're talking about?

'Sink' circuits make a connection to ground through an N-channel MOSFET.  These are typically used to activate a playfield feature (coil, motor, flashlamp, etc), where one side of the feature is connected to the required DC voltage, and the other side is grounded when the MOSFET is activated.

'Source' circuits make a connection to a source voltage through a P-channel MOSFET.  These are typically used to activate a column in a lamp/LED matrix.  The matrix rows are connected to 'sink' circuits so that individual lamps/LEDs in the active column can be lit by completing the path to ground.


How much current can be sourced or sunk through these boards?

The boards can handle sustained currents of 4 amps and short bursts much higher.


What kind of circuit protection do these boards have?

Each bank has a 5x20mm fuse to protect against short circuits.  The boards come with 4 Amp fuses.  Depending on your application, you might need to replace these with different fuses.

Each board monitors the RS-485 serial bus.  If the serial connection is lost, all outputs are disabled immediately.

Power Driver 16 boards have flyback diodes on each circuit to protect the transistors from collapsing magnetic fields resulting from coils turning off.

Each board has buffers to isolate most of the digital logic from the transistor circuits.  These will hopefully help minimize damage in the event that a transistor fails.


How many boards can I chain together?

While there's no specific limit to the number of boards you can use, the P-ROC can currently only uniquely address 8 boards (16 banks).


Can I replace the large power/driver board in my existing machine with these boards?

An RS-485 master must be connected to a P-ROC or another device that can issue the proper commands to the driver boards in your chain.  So you can do this if you'll also be replacing the CPU board with a P-ROC.  Be prepared to change a lot of wiring since the existing wiring harness plug directly onto these driver boards.

We are considering designing another board that will make these driver boards work with original WPC and Stern (Whitestar and SAM) CPU boards.  If this is something that interests you, please  This email address is being protected from spambots. You need JavaScript enabled to view it. privately so I can gauge interest.


Can I supplement the functionality of an existing power/driver board in my machine with these driver boards?

Absolutely!  The P-ROC can control the existing p/d board and new driver boards at the same time.  Just make sure to set the driver board addresses so they don't overlap the functionality of the existing p/d board.


How many boards are needed to approximate the features of a WPC or Stern machine?

WPC/WPC-95 machines use 32-48 direct drivers and an 8x8 lamp matrix.  Therefore you would need 3 Power Driver 16's and 1 Power Driver Matrix 8x8, and one of those 4 boards will need to be a Master Combo to initiate the chain.

WPC equivalent

WPC equivalent configuration


Stern SAM/Whitestar machines use 32 direct drivers and a 10x8 lamp matrix.  Therefore you would need 2 Power Driver 16's and 2 Power Driver Matrix 8x8's, and one of those 4 boards will need to be a Master Combo to initiate the chain.


Stern equivalent

Stern equivalent configuration


If my game is really simple, with just 2 flippers, 2 slingshots, and a 4x4 lamp matrix, can I use one driver board?

It's possible.  A Power Driver Matrix 8x8 / Master Combo might work for you.  You would use 4 transistors in each bank for your lamp matrix, leaving 4 transistors in bank B for your flippers/slingshots.  You can do this, but be careful about your voltages since you can only supply one DC voltage to each bank, and bank A of the Power Driver Matrix 8x8 can only handle up to 20V.


Can I use a driver board to control an RGB LED that requires pulse-width modulated controls?

Yes, that's exactly what the PD-LED board does!  It controls up to 28 RGB LEDs per board, with independent and automatic PWM control of each.


What polarity data should I send to the boards to turn on a Sink circuit?  What about a Source circuit?

All circuits are active high from the controller's point of view (P-ROC, Arduino, etc).  So a 1 will turn on a circuit, and a 0 will turn off a circuit, regardless of whether it's a Sink or Source.  The logic on the boards takes care of driving the transistors properly.  To be clear, these data bits that turn a sink or source circuit on or off are encapsulated, along with some other fields, into a multi-byte transaction command.  Please refer to any of the Power Driver board specs for more details.


Can the driver boards be driven by an Arduino or some other microcontroller?

Yes, any microcontroller capable of driving out data at 8 MHz can drive our driver boards.  You can use one of our Master or Master Combo boards to start the RS-485 chain, or you can use any 3rd party RS-485 transmitter with a fast enough transciever.  Be aware that our Power Driver Master and Master Combo boards require a 3.3V data signal; so a 5V source must be level-shifted down to 3.3V to avoid damaging the board.  The 5V Mini RS-485 Master would be the most appropriate master for a 5V micrcontroller.

With a 16-MHz Arduino, we recommend using the SPI port (MOSI pin) configured with SPI_CLOCK_DIV2.  Here is a sample Arduino sketch.


Can I build a custom driver board and add it to the chain?

Sure.  Any RS-485 receiver that works fast enough to receive the 8 MHz data should be able to interface to the chain.  The RS-485 protocol is defined in any of the existing Power Driver board specs.

If you need help, feel free to This email address is being protected from spambots. You need JavaScript enabled to view it..



Are there plans to offer other types of driver boards?

Various new products are being considered.  Feel free to  This email address is being protected from spambots. You need JavaScript enabled to view it. with your suggestions.