As featured in the blog post "Prototype Post-Mortem: Four-Step Octaved Sequencer", these are the prototype PCB designs for a (yet to be totally finished) fun little noise toy.
The PCB and its electronics are possibly available as a DIY electronics kit. This repo serves as the assembly guide for the kit, as well as the EAGLE project so you can fabricate your own from scratch, should you want to!
Demo video: https://vimeo.com/501110534
|C1||10uF||Polarized, electrolytic capacitor||Tempo timer|
|C2||.1uF||Ceramic capacitor||104||556 IC bypass|
|C3||10nF||Ceramic capacitor||103||Pitch timer|
|C4||.1uF||Ceramic capacitor||104||4017 IC bypass|
|C5||.1uF||Ceramic capacitor||104||4040 IC bypass|
|C6||220uF||Polarized, electrolytic capacitor||Amplifier|
|D1||Diode||Step 1 output|
|D2||LED||Step 1 indicator|
|D3||Diode||Step 2 output|
|D4||LED||Step 2 indicator|
|D5||Diode||Step 3 output|
|D6||LED||Step 3 indicator|
|D7||Diode||Step 4 output|
|D8||LED||Step 4 indicator|
|IC1||556||556 Dual 555 timer||Timers for tempo (on left) and pitch (on right)|
|IC2||4017||4017 counter/divider||Decade counter for steps|
|IC3||4040||CD4040 or MC14040, 12-stage binary/ripple counter||Divides pitch frequency into octaves|
|IC4||386||LM386, low voltage audio power amplifier||Amplifier|
|J1||ON/OFF||Header connection||For external switch (not included)|
|J2||- 9V +||Header connection||9v battery snap|
|J3||- SPK +||Header connection||To 8ohm speaker|
|R1||680||Resistor||Blue Grey Brown||Max tempo|
|R2||220||Resistor||Red Red Brown||Tempo timer|
|R3||5.6k||Resistor||Green Blue Red||Pitch timer|
|R4||10k||Resistor||Brown Black Orange||Counter pulldown|
|R5||1K||Resistor||Brown Black Red||For step 1 LED|
|R6||1K||Resistor||Brown Black Red||For step 2 LED|
|R7||1K||Resistor||Brown Black Red||For step 3 LED|
|R8||1K||Resistor||Brown Black Red||For step 4 LED|
|R9||10k||Resistor||Brown Black Orange||Mixer for octave 1|
|R10||10k||Resistor||Brown Black Orange||Mixer for octave 2|
|R11||10k||Resistor||Brown Black Orange||Mixer for octave 3|
|R12||10k||Resistor||Brown Black Orange||Mixer for octave 4|
|SW1||4 position SPST DIP Switch||Octave mutes|
|VR2||50K||Variable resistor||503||Step 1 pitch|
|VR3||50K||Variable resistor||503||Step 2 pitch|
|VR4||50K||Variable resistor||503||Step 3 pitch|
|VR5||50K||Variable resistor||503||Step 4 pitch|
- Be sure to match polarity on electrolytic caps, diodes, and LEDs! The longer leg of the LED is positive
- The four ICs don't solder directly to the PCB. Instead, solder the included sockets, then insert ICs.
- IC3 may be marked as either CD4040 or MC14040. The two models are pin-for-pin compatible.
- The J1 (on/off) header is included for convenience if you have a switch you'd like to use. If not, short the two pads together.
All done? Try these ideas:
- Swap out for a bigger speaker to really hear the bass
- Increase gain on the 386 with a 10uF cap between pins 1 and 8
- Try bigger pots for the step tuners
- Increase R1 for reaaalllly looongggg steeeppsssssssss
- Swap R9-12 with pots to get individual volume controls for each octave as they mix together
- The 4040 has 12 "octave" outputs but we're only using four...
This PCB was last updated April 2018. In addition to the issues from the post-mortem:
- Some footprints are slightly mis-sized and require bending leads
- Volume control is linear instead of logarithmic, so range sweep isn't great
- Battery and speaker wires need relief holes to prevent breakage over time
- 1.1.2: Adds IC, header, and polarity labels; reorders octaves
- 1.1.1: Adds mounting screw holes and a header for on/off switch (not included)
- 1.1: Initial version featured in the blog post
Designed by Oskitone. Please support future synth projects by purchasing from Oskitone.
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