• on Audio/Video/Photography
  • Published in issue 3/2002 on page 0
About the article

Relay Extension for DMX Demultiplexer

eight DMX channels for eight relays

The DMX demultiplexer, which was described in Elektor Electronics recently, enables you to drive eight analogue outputs with a control voltage from 0 to 10 V, a standard that is used for many lighting installations. For less elaborate equipment, such a control voltage is not actually necessary, since the control is limited to either ‘on’ or ‘off’. This is the intended application for this extension circuit which provides eight relay outputs.The remote control of lighting installations with voltage or current is still very common nowadays, despite the existence of DMX512. In all likelihood either because the design is quite old (dimmers mostly), or because it is equipment where the additional costs of a digital interface would be unjustifiable (stroboscopes, smoke generators). This was one of the motivations for designing the 8-channel DMX/10-V interface, which is able to control such equipment directly (refer to Elektor Electronics November 2001).
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Component list
R1-R8 = 1k?
C1,C2 = 33nF
C3 = 100nF
C4 = 10µF 25V
D1-D8 = high-efficiency LED
D9-D16 = 1N4148*
IC1 = 74HCT164
IC2 = 74HCT573
IC3 = ULN2803
IC4 = 7812
IC5 = 7805
K1-K8 = 2-way PCB terminal block, lead pitch 7.5 mm
K9 = 20-pin IC-socket
Re1-Re8 = E-Card relay, 12V, type V23057 B0002 A101 (330 ?) (Siemens)
Length of 20-way flatcable with DIL20 IDC connectors
PCB no. 010002-2
* D9-D16 may be omitted because the ULN2803 has internal flyback diodes.
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