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MIDI Lights & Slide Control

controlling slide projectors with MIDI commands

MIDI Lights & Slide Control
In the January 2001 issue we showed that it was possible to control other things with MIDI besides the usual musical instruments. This time, MIDI signals are used to control light sources. There are four adjustable triac outputs and eight relays to control, for instance, four slide projectors.When controlling lights, it is not easy to maintain synchronisation between light and sound when the control signals reside on different media. There exist a plethora of professional equipment that make synchronisation possible, but usually have a price tag attached that is well beyond the means of the amateur. Cheaper systems may have limited expandability and often cannot be interconnected with systems from a different brand.Hence the idea to control (slide) projectors and relays via MIDI, where ‘light events’ can be manipulated with a MIDI/audio-sequencer. Synchronisation is no longer an issue, since everything is now controlled from a PC. By using MIDI as the medium, the application of the MIDI lights is now independent from any hardware or software. If you have at your disposal a MIDIsequencer with audio capabilities, then it is possible to mix the sampled audio with MIDI. And, if this sequencer possesses more than one separate MIDI-output, then it becomes possible to connect multiple light controllers.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info / Update
A few readers have reported lamp flicker when the control is operated. No problems are observed with constant brightness. Flicker may be suppressed by lengthening the synchronisation pulse. This is easiest done by increasing the value of C1 and C2 to 3.3 nF
Component list
(All resistors SMD case # 1206)
R1,R2,R31 = not fitted
R3 = 150 Ohm
R4,R6,R9,R10,R35-R38 = 1k Ohm
R5,R25 = 220 Ohm
R7,R8,R12,R13 = 10k Ohm
R11 = 270k Ohm
R14 = 2k Ohm 2
R15 = 4k Ohm 7
R16 = 8k Ohm 2
R17,R18,R22,R24 = 82 Ohm
R19-R21,R23 = 680 Ohm
R26,R40...R43* = 100k Ohm
R27-R30=VDR 48-96 V, e.g., Siemens S10K50 or S07K50
R32,R34 = 270 Ohm
R33 = 100 Ohm *
P1 = 5k Ohm preset, 'ordinary' vertical model or Bourns type 3386
C1,C2,C20 = 2nF2
C3,C13 = 33pF
C4,C9 = 10µ F 16V radial
C5,C6,C7,C14-C19 = 100nF, lead pitch 5mm
C8 = 1000µ F 25V radial
C10,C11 = 1µ F 16V radial
C12 = 3nF3
C14 = 100pF
D1,D4-D7 = LL4148 (SMD)
D2,D3 = 1N4001
D16 = LED, green
D17 = LED, yellow
IC1,IC8,IC9,IC10 = MOC3020 (QT, formerly Motorola: www.qtopto.com)
IC2 = 7805
IC3 = PC900 (Sharp)
IC4 = LM339
IC5 = 555
IC6 = SAB80C535-N
IC7 = 74HC573
IC11,IC12 = ULN2803
IC13,IC16 = 74HC4049
IC15 = 27C256, programmed, order code 000179-21
K1-K10 = 5-way DIN socket, PCB mount, pjns arranged at 180°
K11 = 15-way sub-D socket (female), PCB mount, angled pins*
K12 = 2-way PCB terminal block, lead pitch 7.5 mm
X1 = 12 MHz quartz crystal
F1 = fuse, 100 mAT (time lag), with PCB mount holder
S1 = 4-way DIP switch
T1 = mains transformer, sec. 2 x 9 V/ 4.5VA (e.g., Monacor/Monarch VTR4209)
JP1 = 2-way pinheader
68-pin PLCC socket
Heatsink for IC2, e.g., SK104-50 (Fischer, Dau Components)
Re1-Re8 = 12-V relay (e.g., Zettler AZ5Y-1C-12DE or Siemens V23101-D6-A201
Enclosure type LC650 (Eurodis, Bolton)
PCB, order code 000179-1
Disk, contains sourcecode and binary file, order code 000179-11
* optional, for extensions
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