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Power Distribution

As I've expanded my 6502 system, power distribution has been a challenge at times. My initial 6502 was built on BusBoard Prototype Systems BB830 breadboards (included with Ben's 6502 kit). Adding the VGA circuit to my breadboard system increased power requirements and raised potential issues of noise and sporadic issues when the power dropped too low.

Benchtop DC Power Supply
Benchtop DC Power Supply

At one point, I experimented with a 6502+VGA build on Elegoo breadboards, and power distribution proved to be very challenging. Connectivity was erratic, and I would experience notable power drops between breadboards.

I built a two-layer, independent VGA PCB, and I found the power and signal distribution was pretty good. I eventually built a four-layer 6502+VGA PCB, with nice results for power and signal.

That brings me to my current setup. It includes a 6502 with five VIAs, VGA, Sound, SPI, a pair of Arduino Megas, three Arduino Nanos, an Arduino Due, and breadboards for additional expansion.

Current System
Current System

To help with power distribution, I built a PCB specifically designed to help distribute power from my benchtop DC power supply to the different components of the system.

Power Distributor PCB
Power Distributor PCB

While I hope to continue to improve the power distribution, the current setup seems to be working pretty well for me. Key aspects of the approach I have taken up to this point:

  • I am using an inexpensive benchtop DC power supply, a TACKLIFE MDC01.

  • I built cables that connect my power distribution PCB to the power supply. The cables are approximately four feet long, with three feet being 12-gauge from the power supply and one foot being 16-gauge to a barrel connector.

Power Cables
Power Cables
  • The power distribution PCB then breaks out the power to seven barrel connectors, seven screw terminal connectors, and eight pin header connectors; of these, so far I am using five barrel connectors (plus the connection to the power supply). I am primarily using 1000µF electrolytic capacitors on this PCB. Trace track widths are at 0.508mm.

Populated Power Distributor
Populated Power Distributor
  • A one-foot barrel connector cable (16-gauge) connects the 6502+VGA PCB to the power distribution PCB.

  • All four PCBs (power distributor, 6502+VGA, sound, SPI) are four layer PCBs with VCC and GND inner layers.

  • The far right edge of the 6502 PCB has a number of screw terminal connectors for power distribution to breadboards.

  • Each IC on my PCBs has a pair of capacitors – a 0.1µF and a 0.01µF.

  • Each PCB has one or more 100µF capacitors.

  • Two additional barrel connector cables (22-gauge) connect the sound and SPI cards to the power distribution PCB.

  • Three Arduino Nanos on the SPI card are powered from USB to screw terminal connections on the SPI card.

  • The pair of Arduino Megas is powered from USB to barrel connectors on the power distribution PCB.

  • The Arduino Due is powered from the PC, as it has to be connected to the PC for 6502-to-PC communication.

Power Connections
Power Connections

With this setup, I am currently supplying 5.09v at approximately 750mA from the benchtop power supply. I am getting a 40mV voltage drop from the power supply to the power distributor. I am getting an additional 40mV voltage drop between the power distributor and the bottom (far end) of the 6502+VGA PCB. I see a slight drop when the LED bar graphs are fully lit up.

Future Possibilities

I would love to use a card slot expansion setup at some point, where I can better distribute signal and power.

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