Expanders for the Turing Machine Random Looping Sequencer

Here are two expanders for the Turing Machine / Random Looping Sequencer.

Turing Machine ExpandersThere are three parts:

  • A backpack for the RLS board. This adds expander headers and reverse polarity protection to the main module.
  • Pulses: a random, looping clock divider, with seven pulse outputs, controlled by the main module. The clock length follows the clock input, so can be controlled if you have a square wave LFO with pulse width modulation.
  • Voltages: an eight stage random looping step sequencer with illuminated faders, controlled by the main module. Unusually, any number of stages can be active at once, creating unpredictable results. It has two outputs, one normal – with a scale control that works in the same was as the similar control on the main module – and one inverted. The inverted output has a ‘shift’ control which raises (offsets) the voltage by up to 9 volts. This means you can drive positive-only modules (i.e. quantizers) with the inverted output.

One RLS with a backpack can control one Pulses module and one Voltages module. With a bit of hacking, you could probably connect two Pulses or two Voltages, if you wanted.

All three are fast, simple builds. If you managed to build a RLS, you can definitely build these. If you bought an RLS but would like to try DIY, these could be a place to start.

Random Looping Sequencer ExpandersLike the Turing Machine, this is a completely open source project. The schematics, Eagle CAD files, Gerbers, laser-cuttable panel designs and Mouser BOMs are all available under a Creative Commons license that permits unlimited commercial use.

One of the people making use of that license is Thonk in Brighton, who are offering full kits for all three expander PCBs. (Muffwiggler thread on Thonk kits)

Documentation and build documents

(All CC licensed)

This shows the back of the modules, with the backpack on the main module and the pulse module to one side.

The latest version is v2.1, which fixes the capacitor polarity issue in v2. V2 schematics and documents are below.

Random Sequencer Expander Documentation v1

– This PDF file contains block diagrams, how the circuit works and how to build the PCB.

RLS Expander Schematic PDFs

Eagle and Gerber Files

You can send these Gerber files directly to a PCB fabricator to make boards. The process is explained here.

RLS Backpack v3 Eagle

RLS Backpack v3 Gerber Files

RLS Pulse Expander Eagle v2

RLS Pulse Expander Gerbers v2

RLS Volatages rev1 Eagle

RLS Voltages  rev1 Gerbers


These are illustrator files suitable for laser cutting acrylic panels.

RLS expander panels 1+2 PDF

RLS Expander Panels 1+2 PDF+Illustrator

Mouser BOMs

Backpack (£4.50 in May 2013)

Pulses (£1.74)

Voltages (£21.02 –  faders!)

Licence: This is an open source hardware project. You can use this design however you like, including any modification or commercial production, so long as you credit Tom Whitwell and share your own changes. Random Sequencer by Tom Whitwell is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

Creative Commons License












  1. Robert says:

    At the moment there are no 2k resistor networks available, only the 2k2. Can i use them instead? I don’t want to wait three month or longer till they available.

    Best regards


  2. Joe says:

    Hi Tom,
    I have a complete turing system w/ expanders and an extra turing machine and am having the following problem. With a square clock triggering the Turing and all notes off i am getting the clock signal sent to slider 2 on voltages producing an audio signal, no other sliders or Pulses is affected. I’ve re-soldered the backpack and voltages sometimes causing other problems like all even sliders working or odd sliders. I’m assuming the problem is on the backpack, Any thoughts?

  3. andrew says:

    How do all of the new expanders connect to one mk2 Turing Machine? I had heard that you can connect 1 Voltages, 1 Pulses and 2 or even 3 Volts but there are only 2 expander ports on the Turing Machine…?

    • Tom Whitwell says:

      The expanders have two ports on the back, so can be daisychained

    • Tom Whitwell says:

      No, looks like a soldering issue – check the outputs (could be reversed LED, with the output working). Check you’ve soldered both sides of the relevant resistors on the back.

  4. Andrew says:

    Thanks! I just finished the Pulses mk2 and all work except the 1+2/+7 output–neither the jack or led functional. I reflowed joints all looks good. What else should I check?

  5. Andrew says:

    Never mind! I didn’t realize that the 1+2/4+7 jack won’t output often unless there’s enough pulses to cover all those jacks. Works great, Turing setup complete and rocking. Brilliant!

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