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MB-LRE8x2CS PCB / 16 LEDrings/Encoders Control Surface

Welcome to the wiki page of the control surface board featuring combo DINx4 and improved DOUTx4 modules with 16 LEDrings and 16 encoders.

You can find the tread of the PCB design here.

The last revision of the PCB is rev 2.5.

It is a very practical and cheap way to make a midi controller with adding only a core or make a more important controller without having to wire LEDrings.


The PCB have components soldered on the two sides.
Top side: Encoders and LEDs.
Back side: All others components (see BOM below).

The PCB is two sides white silkscreened on green FR4 material, 1.6mm thickness, 1Oz copper, HASL, 100% E-tested & ROHS compliant.

The board is 3,368 x 13,472 inch (342,2mm x 85,5mm): just less than 2U standard.
The diameter of each LEDring is 1,299 inch (33 mm) with the use of 3mm LED.


Protoboard (note this is not the last version but has same dimensions and LEDs/Encoders positioning):
Protoboard in action:

You can see the LEDring animation in this poorly quality video.



You can download a better definition version here.



You can download a better definition version (without ground surfaces for better visibility) here.


You can download Top silkscreen here.

You can download (mirrored) Bottom silkscreen here.



You can download a better definition version here.


The origin (0;0) is the bottom left corner of the board.


You will find the coordinates of LEDs/Encoders in this files (new version with better accuracy positioning!).

3mm board holes

Coordinates of the six holes (in inch):

0,16 0,16
6,736 0,16
13,312 0,16
0,16 3,208
6,736 3,208
13,312 3,208


2ULN2803 Transistors Darlington arraysULN2803#1, ULN2803#2ULN 2803A595-ULN2803ANoptional
810k 6 Pin SIL resistor networkRN3, RN4, RN5, RN6, RN7, RN8, RN9, RN10SIL 6-5 10K264-10K-RC
474HC165IC1, IC2, IC3, IC474HC 165511-M74HC165
474HC595SR1, SR2, SR3, SR474HC 595511-M74HC595
8Ceramic Cap 100nF=0,1uF “104”C1, C2, C3, C4, C6, C7, C8, C9Z5U-2,5 100n80-C412C104K5R
1Polarized Electrolytic Capacitor 100 uFC5rad 100/16140-REA101M1CBK0611P
2220 Ohm 16 Pin DIL resistor networkRN1, RN2-652-4116R-1LF-220or 16x Resistor 220 Ohm
16220 Ohm metal film resistor8 for RN1, 8 for RN2METALL 220MF1/4DCT52R2200FInstead the 2 RNs above
22-row DIL Header (2×5 pins)“IN”, “OUT”SL 2X10G 2,54649-67996-420HLFFor Reichelt, buy only 1 item and cut it in 2 parts
11-row SIL Header (1×16 pins)“TO_SWITCH_BOARD”SL 1X36G 2,54649-68001-416HLFoptional
16PEC16-4020F-N0024ENC1, ENC2, … , ENC16-652-PEC16-4020FN0024Undetended - without build-in switch
orPEC16-4020F-S0024 -652-PEC16-4020FS0024Undetended - with build-in switch
10Socket 16 pins-GS 16571-1-390261-4
2Socket 18 pins-GS 18571-1-390261-58 (NOT 9) bridges to solder if not using ULN2803s
256LED 3mm or rectangular (2x5x7mm)LED1, LED2, … ,LED256LED 3MM RT-Reichelt model recommended

This is a Mouser Orderlist (Thank you Lamouette). You have only to add your LEDs and Pinheaders.

LED black list

Since Tk discovered a brightness problem with some rectangular 5x2x7mm LEDs, we found it useful to create a list of LEDs wich are successfully or unsuccessfully tested. Members are welcome to edit this page to add their LED feedback.

ModelTypeLinkGoodNot goodCommentAuthor
Kingbright WP103HD5x2x7mm rectangularMouser X Tk
LED 3MM RT3mm roundReichelt X Tk
“10001”5x2x7mm X X Used without ULNs(prototype)Fairlightiii
Kingbright L-934ID3mm roundSegor Electronics X rvlt
Kingbright WP132XID3mm roundMouser X Used without ULNsgrizz
Kingbright WP132XID3mm roundMouser X Used withMIDIbox NG & ULNsMaG2k
Kingbright WP113SRDT5x2x7mm rectangularMouser X Used withMIDIbox NG & ULNsMaG2k
smashTV is selling3mm roundsmashTV X Used withMIDIbox NG & ULNsMaG2k
Tayda Electronics3mm roundTayda Electronics X Used withMIDIbox NG & ULNsMaG2k


LEDs & LEDring

Each LEDring is composed of 16 LEDs.
You can use 3mm LEDs or 5x2x7mm rectangular LEDs (because the different angles of the LEDs in the LEDring) or all other LED with 0.1 inch (2,54 mm) leads spacing.
There's not enough space for 5mm LEDs.


The LED polarity: the cathode (short leg) has to show to the center of the LED ring:

LED polarity

You can use 16mm “standard” encoders (ALPS STEC16, Bourns PEC16-4xxxF-Nxxxx series, encoders sell by voti, …).
You can use instead PEC16-4xxxF-Sxxxx series (with built-in switch). Probably others built-in switch encoders comply the PCB footprint but you have to compare before datasheets.

16 pins SIL header

If you use switched encoders, one of the two pins of the built-in switch is grounded while the other pin is connected to a pin of this SIL connector.

The silkscreen include the name of each switch.

2x5 pins DIL headers

They are 1:1 with J8/J9 of Core8/Core32/LPC17 so you can use practical IDC female Connector or still more easier pre-built 2x5 Pin IDC Ribbon Cable.

Be careful to the connection to the MBHP_CORE_LPC17 module because it could be confusing, since the SO pin of J8/9 has to be connected to the SI pin of the LRE2x8 board, and SI to the SO pin (for MBHP_DOUT/DIN we usually have the same names for these signals, this detail has been overlooked).


This component provide more current to the matrix LED than the 74HC595 shift registers can and improve the brightness of the LEDs.
You can use or not Transistors Darlington arrays.
In the second case (and only in this case), you need to bridge 16 of the 18 free pins 2 by 2 (in red on the picture):

Be careful to not bridge the 2 last pins
(those opposite to the “head” of the chip).
DIP switchDIP switch
An idea is to use e.g. DIP16 Switch. (NT 08 at Reichelt).
220 Ohm 16 Pin DIL resistor network

As in the SmashTV's PCB, you can replace a DIL resistor network by 8 resistors.
In this case I recommend to use 1% metal film resistors because with the tolerance of standard carbon resistors you could see maybe different brightness of each LED of the LEDring.

10kOhm 6 Pin SIL resistor network

Be careful when sourcing SIL resistor networks because a 6 Pin SIL resistor network can be 5 commoned resistors (what you need here) or 3 independant resistors.

Polarized Electrolytic Capacitor 100 uF

It is the only polarized cap of the board. The silkscreen indicate the “+” and “-” signs on the board.

Diagram interconnection

One board connection
Diagram interconnection

Only one 2×5 Pin IDC Ribbon Cable is necessary to connect the board.

Global interconnection
Diagram interconnection
You can download a better definition version here.

You can chain 4 of this board or connect yours extra DIN/DOUT modules e.g. on the DIL connector named “OUT”.
You can connect also this board at the end of the chain and connect this board with the “IN” connector after yours others modules.

With the use of the upcoming MIDIbox NG (planned for Winter 2012/13) you will be able to have 2 chains of 4 boards each (2x4x16=128 encoders and 2x4x16=128 LEDrings).


For an eventual next revision of the PCB, this is a list of improvements that members are free to complete:

  • Changing IN/OUT sockets by polarized sockets and improving the silkscreen (to avoid confusing SI/SO pin). Tk Done
  • Moving cap C5 (too close to the IN socket). Tk Done
  • Trying to move some critical vias. Fairlightiii Done
  • What about the use of ULN2803s? Fairlightiii Let them here for 8×2 configuration, not present on upcoming 4×2 and 8×1 boards
  • Trying to add DINX2 onboard to handle the 16 encoder switches (start/end of the chain?). Fairlightiii Not planned to be implemented
  • What about the size of the PCB? Fairlightiii Slightly less big (I won some mm in the edges)
  • new arrangment of encoders and LED-rings in 4×4 matrix? MaG2k Upcoming 4×2 and 8×1 boards
mb-lre8x2cs_pcb.txt · Last modified: 2016/06/22 00:03 by psykhaze