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UNVERIFIED - DRAWN, NOT BUILT. This circuit and this layout were drawn up and checked by script and in Copper Bottom, and the editor's checks come back clean, but nobody has soldered it yet. Every value and voltage on this page is arithmetic and datasheet. Build it once, fix whatever fought back, and this banner comes off.

Mantis

Eight-step up/down sequencer · By Onion Madder · Mess O' Pedals

An eight-step sequencer that runs forward or backward. Eight knobs each set one step, a clock walks through them, and one toggle decides which way it walks. It does not make a sound of its own: it makes a stepped voltage, a CV, for the pitch input of another build, so a VCO with a CV jack plays a little eight-note pattern that you can flip into reverse.

The Mantis drawn as a stripboard diagram, titled Mantis, 36 by 13 stripboard. Thirteen orange copper strips lettered a to m run left to right under 36 numbered columns. Three chips stand in a row: U3 CD4051 at the left, U2 CD40193 in the middle and U1 CD40106 at the right, each with a column of gray X cut marks between its pin rows. Strip a along the top carries plus V and strip m along the bottom carries ground. Between U3 and U2 two long dark blue links drop from the counter's outputs to the switch's select pins, two resistors stand between the counter's clock pins and strip d, and four STEP pads sit beside U3's right-hand pins; four more STEP pads and the output resistor R5 are at U3's left. Around U1 are C1, R1, R2 and the RATE and DIR COM pads, with short links between neighboring pins. D1 sits at the top left. Around the board the panel parts are drawn with a wire to every pad: the eight step pots, the RATE pot, the DIR and power toggles, the blink LED, the output jack and the DC jack. Below, the same board is drawn again from the solder side, mirrored, every solder point a dark dot and each chip as an outline with pin 1 boxed. A parts list and an OFF THE BOARD block, one line per panel part, run underneath.
The Mantis, 13 strips by 36 holes. Copper Bottom draws the component side on top, then the same board from the solder side with the columns running the other way, so a cut is the same hole in both pictures. The panel parts sit around the board with a wire to every pad, and the OFF THE BOARD block at the bottom says where each leg goes.

What you'll need

tap to expand / collapse

Three chips, eight small parts and 19 links on the board, and a box full of knobs off it. Every chip solders straight to the board.

  • 1× CD40106 hex Schmitt inverter, DIP-14 (U1) - spot it: fourteen legs, CD40106 or HEF40106 on top. It is the clock
  • 1× CD40193 up/down counter, DIP-16 (U2) - spot it: sixteen legs, CD40193 on top. Not a CD40192: that one counts to ten and would never reach some of the steps
  • 1× CD4051 eight-channel switch, DIP-16 (U3) - spot it: sixteen legs, CD4051 or HEF4051 on top
  • 3× 10K resistor (R1, R3, R4) - spot it: brown-black-orange. R1 is in series with the RATE pot; R3 and R4 hold the counter's two clock inputs high
  • 1× 2.2K resistor (R2) - spot it: red-red-red. It feeds the blink LED
  • 1× 1K resistor (R5) - spot it: brown-black-red. It lies along strip f over a cut, in front of the output
  • 1× 2.2 µF electrolytic (C1) - spot it: a small can with a stripe down one side marking the negative leg; the file shows which way it goes. It sets the clock's range
  • 1× 100nF ceramic (C2) - spot it: printed 104. The counter's supply bypass
  • 1× 1N5817 Schottky (D1) - spot it: fat black body, gray band. It stops a supply plugged in backwards
  • 19× wire links - offcuts of component leg. One, J11, runs under U2's body; that is ordinary

Off the board

  • 8× B100K linear pots - STEP 1 to STEP 8. Each one's lug 3 goes to +V and lug 1 to GND, daisy-chained from pot to pot, and its wiper to its own STEP pad
  • 1× B500K linear pot - RATE, wiper and one outer lug
  • 1× SPDT toggle - DIR, forward or backward
  • An SPST toggle for power, in the supply's plus lead before the board's +9V pad. Every build on this shelf gets one, and the drawing above shows it
  • 1× 5 mm LED - it blinks with the clock
  • 1× 3.5 mm jack - the CV out
  • 1× 2.1 mm DC jack for a 9 V center-negative pedal supply
  • A box with room for nine knobs, two toggles, an LED and two jacks. Nobody has drawn a drill template for this one yet

The layout file is the guide

Like every layout on this shelf, the build document is the file: ↓ Download Mantis.json - import it into Copper Bottom and the editor gives you the board picture, the placement walkthrough, the electrical checks and a printable build sheet, all from the same file. No coordinates are written out on this page on purpose: the editor is the viewer, and a number typed twice is a number that can drift.

Strip a is +V and strip m is ground. R5 lies along strip f over a cut, so its two legs are on different copper even though they share a strip. The chips go in last: solder everything else, do the meter check below, then the chips.

The steps play in order

The counter's three outputs drive the 4051's three select pins, but not in the order you would guess: Q3 drives A, Q2 drives B and Q1 drives C, because that is the wiring that fits the board. So as the counter counts, the 4051 reads its channels as 0, 4, 2, 6, 1, 5, 3, 7. That does not matter to you, because the STEP pads are numbered in the order they play: STEP 1 plays first and STEP 8 last going forward, and the other way around when DIR is flipped.

The netlist

My script wrote this from the design and checked the board against it, and so did Copper Bottom: every connection the netlist names is on the board and nothing on the board is missing from it. Four chip outputs are left empty on purpose, so the netlist does not mention them: U2 pins 7, 12 and 13 (Q4, CARRY and BORROW) and U1 pin 8.

The off-board wiring

PadGoes to
+9VDC jack +, through the power switch
GNDDC jack -, the output jack sleeve, the blink LED's cathode, and lug 1 of all eight step pots
+Vlug 3 of all eight step pots, daisy-chained
OUToutput jack tip: the stepped CV, into another build's CV or pitch input
DIR COMDIR toggle (SPDT) middle lug: the clock
DIR UPDIR toggle (SPDT) one end lug
DIR DOWNDIR toggle (SPDT) other end lug
RATE WIPERRATE pot wiper (lug 2)
RATE LUGRATE pot lug 3 (lug 1 empty)
BLINKblink LED anode (long leg); its cathode to GND
STEP1step pot 1 wiper
STEP2step pot 2 wiper
STEP3step pot 3 wiper
STEP4step pot 4 wiper
STEP5step pot 5 wiper
STEP6step pot 6 wiper
STEP7step pot 7 wiper
STEP8step pot 8 wiper

First power-up

  • Before the chips go in. Plug in the 9 V supply, switch on, and check for about 8.7 V from the GND pad to strip a, and to the holes where the three chips' supply pins go: U1 pin 14, U2 pin 16 and U3 pin 16
  • Switch off, solder the three chips in, notch the way the file shows, and switch on. The blink LED should flash with the clock, and RATE should speed it up and slow it down
  • Set the eight step pots to different places and put a meter on OUT. With RATE slow, the reading should step from one pot's setting to the next, and flipping DIR should send it back the other way
  • Then plug OUT into the CV input of a VCO: the Mosquito 556 and the Opto Duet CV both have one

How it works, in one breath

One Schmitt inverter of the CD40106, with R1 and the RATE pot from its output back to its input and C1 on the input, is the clock: from about one step a second to about fifty, by arithmetic. Two more inverters copy it to light the LED. The DIR toggle sends the clock to one of the CD40193's two clock inputs, CLOCK UP or CLOCK DOWN, and R3 and R4 hold whichever one is not chosen high, which the counter needs before it will count on the other. Its outputs, three bits, choose which of the CD4051's eight channels is joined to its COM pin, and each channel is a pot's wiper sitting somewhere between 0 and +V. COM goes out through R5 as the CV.

Things to try

None of these have been tried, because none of this has.

  • Slower. C1 at 10 µF stretches the clock about four and a half times, into a slow walk
  • A photocell for RATE, across RATE WIPER and RATE LUG, and the pattern speeds up in the light
  • Into the Mosquito 556's CV jack, with its pitch knob setting where the pattern sits

A counter stepping a 4051 through a row of pots is the standard analog sequencer, and belongs to everyone who has built one. This up/down version and its layout were drawn for this site, and anything wrong with them is mine to fix.