koppchen / serge-tkb-led-mod

Small PCB designed to add row indicator LEDs to the Serge TKB.

Serge TKB LED Mod

Small PCB designed to add row indicator LEDs to the Serge TKB (Touch Activated Keyboard Sequencer). This was designed for The Human Comparator TKB version, which was based on the original Serge TKB schematics.

This repo contains the EAGLE board and schematic files, along with the LTSpice schematic for circuit simulation.

LED mod PCB

The LED Mod PCB is small enough to be mounted on the top right corner of the main PCB.

Pads labeled GND, VCC, A, & B are wired to the bottom of CD4520BE on the main PCB. Pads labeled 1, 2, 3, & 4 are wired to the LEDs of sequencer rows A (1), B (2), C (3), and D (4).

Wiring the CD4520BE pins to the LED mod PCB.

Mounted mod PCB

Two nuts will give enough space between the main PCB and mod PCB for the wires.

LED wiring

LED anodes are wired to the mod PCB pads 1-4. LED cathodes are wired to ground.

BOM

Value	QTY	Description	Mouser Part #
CD4051BE	1	CMOS Single 8-Channel Analog Multiplexer/Demultiplexer with Logic-Level Conversion	595-CD4051BE
R1	1	4.99k Resistor
R2	1	1.2k Resistor
	4	Standard LEDs - 3mm Red 25mcd 640nm 40 deg Diffused	604-WP710A10LSRD
	4	LED Lenses Red Fresnel 3mm Lens	593-1700R

Resources

Serge TKB Schematics:
http://machines.hyperreal.org/manufacturers/Serge/schematics/