Introduction: Atari Punk Console With a Baby 8 Step Sequencer

About: Bantam Tools desktop CNC machines provide professional reliability and precision at an affordable price. (Bantam Tools was formerly Other Machine Co.)

This intermediate build is the all-in-one Atari Punk Console and Baby 8 Step Sequencer you can mill on the Bantam Tools Desktop PCB Milling Machine. It’s made up of two circuit boards: one is a user interface (UI) board and the other is a utility board. The design utilizes three 555 timers and a 4017 decade counter to emit a square wave and sequence a repeating series of frequencies.

Step 1: Gather Your Tools, Materials, and Files


Bantam Tools Desktop PCB Milling Machine

Computer with Bantam Tools Desktop Milling Machine Software installed

Flat end mill, 1/32"

Flat end mill, 1/64”

Alignment bracket

Soldering iron

Diagonal wire clippers


PCB blank, FR-1, single-sided

PCB blank, FR-1, double-sided

Tape, high-strength, double-sided

Battery, 9V

Potentiometer, 100K (10)

Potentiometer, 1M

Diode, 1N4148 (8)

LED, 5mm (9)

Resistor, 1K (12)

Male header, 0.1”, 19mm 1x9 (2)

Female header, 0.1”, 12mm 1x9 (2)

Dip socket, 2x4 (3)

Dip socket, 2x8

555 timer (3)

4017 decade counter

Electrolytic capacitor, 47uF (2)

Screw terminal, 2x1

Stereo jack, horizontal, 3.5mm

Slide on/off switch




Step 2: Set Up Your Job

Before you begin, install and locate the alignment bracket. Then, under Fixturing, select Locate and follow the instructions on the screen. Using the alignment bracket will ensure that your board is perfectly squared in the front left corner of the spoilboard.

Now it’s time to set up your job.

Note: For more guidance on loading your tool and entering information into the Bantam Tools Desktop Milling Machine Software, refer to the Light-Up PCB Badge project.

  1. Connect the Desktop PCB Milling Machine to your computer and open the Bantam Tools Desktop Milling Machine Software.
  2. Home the mill.
  3. Double-check to make sure it says Bracket under Fixturing.
  4. Select the 1/64" Flat End Mill, load it with the bit fan attached, and locate the tool.
  5. In the Material dropdown menu, select Single-Sided FR-1.
  6. Measure and enter dimensions in the X, Y, and Z values under Material.
  7. Put high-strength, double-sided tape on one side of the PCB, and adhere it onto the spoilboard so it aligns with the left corner of the alignment bracket.

Note: Remember to account for the thickness of the high-strength, double-sided tape. The tape is 0.006” thick. Enter this for the Z value under Plan Placement.

Step 3: Import the File for the UI Board

If you haven't already, download the APC/Baby8-UI-Board file. Then, in the Bantam Tools software, under Plans, click Open Files and select the APC/Baby8-UI-Board file. Under Plan Placement, be sure that Bottom is selected. Next, select the 1/64" Flat End Mill.

Your mill time will vary depending on the speeds and feeds recipe you use. For this operation, we used the following recipe for the 1/64" flat end mill:

  • Feed Rate: 50 in/min
  • Plunge Rate: 15 in/min
  • Spindle Speed: 20,000 RPM
  • Stepover: 49%
  • Pass Depth: 0.007 in

If you’d like to adjust your speeds and feeds to match ours, click File > Tool Library > Add Tool. Name your new tools and then input the speeds and feeds recipe. Learn more about customizing your tool library in our dedicated guide.

Step 4: Start Milling

When you’re done setting up your file, click Start Milling.

When prompted, swap out the 1/64" flat end mill and replace it with the 1/32" flat end mill. We used the following speeds and feeds recipe for the 1/32" flat end mill:

  • Feed Rate: 60 in/min
  • Plunge Rate: 15 in
  • Spindle Speed: 22,000 RPM
  • Stepover: 49%
  • Pass Depth: 0.010 in

Once you’re finished milling the UI board, remove it from the mill, remove the tape from the board, and clean any debris on the spoilboard.

Step 5: Mill the Double-sided Utility Board

Measure your double-side FR-1, enter the dimensions into the software, prep your stock, and insert it into the Desktop PCB Milling Machine.

Download and import the APC/Baby8-Utility-Board file. Then follow the steps outlined in Step 2. When you’re ready, click Start Milling.

For this step, you’ll need to do both a flip operation and a tool change on both sides of the board. Swap the 1/32” flat end mill for the 1/64” flat end mill when prompted. When the machine is finished milling the first side of the board, remove it from the PCB and spoilboard, re-tape the PCB, and flip it over so that it’s aligned with the front right corner of the spoilboard. Again, under Plan Placement, be sure that Bottom is selected.

Once the board is done being milled, remove it from the machine and remove the tape from the board.

Step 6: Solder the Components

Collect the components you need for each board.

UI Board Components (Single-Sided Board):

  • Potentiometers, 100K (10)
  • Potentiometer, 1M
  • Diodes, 1N4148 (8)
  • LEDs, 5mm (9)
  • Resistors, 1K (10)
  • Male headers, 0.1”, 19mm (2)

Download the schematic for the UI board.

Utility Board Components (Double-Sided Board):

  • Dip sockets, 2x4 (3)
  • Dip socket, 2x8
  • 555 timers (3)
  • 4017 decade counter
  • Electrolytic capacitors, 47uF (2)
  • Screw terminal, 2x1
  • Horizontal stereo jack, 3.5mm
  • Female headers, 0.1”, 12mm 1x9 (2)
  • Slide on/off switch
  • Resistors, 1K (2)

Download the schematic for the utility board.

The UI board contains 11 potentiometers, eight of them are for defining the sequencer’s pitch, while the other three control the tempo, pulse width of the oscillation, and the volume.

Each of the eight pitch-variable resistors is connected to an output pin of a 4017 decade counter (located on the utility board underneath) and counts through the 8-step sequence. As each step is passed, the emitted voltage—as determined by the position of the pot—is applied to oscillator A of the APC, affecting its frequency. There’s an LED located above each step to indicate which one is being played. The 1N4148 diodes prevent noise from unintended steps. The UI board will look like the picture above once it's assembled.

Meanwhile, the utility board contains the decade counter, a 555 timer that serves as a master clock, and two more 555 timers serving as oscillators A and B for the APC. Oscillator A is in astable mode, while oscillator B is in monostable mode, with its trigger coming from the output of oscillator A.

Oscillator B has a pot connected to it for varying the pulse width of the oscillation. The 4017 decade counter emits 10 steps. However, step nine triggers the reset pin, limiting the sequence to eight. The output voltage from the stepped variable resistors are applied to the discharge pin on Oscillator B, dictating the charge rate of the attached capacitor, and ultimately the oscillation frequency.

The design requires a 9V battery. There are “+/–” symbols etched into the top layer of the utility (bottom) board to indicate polarity. Additionally, there are “–” symbols etchings indicating the required notch orientation for the integrated circuit (IC).

Also, each board has an arrow milled on it. These arrows indicate the way the boards should be facing when you stack them. The arrow should be on the bottom of the UI board and on the top of the utility board.

Step 7: Make Some Noise!

Congrats on your all-in-one APC/Baby8. Let’s pop in the battery, plug it into a speaker, and make some noise!

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