Relay Extension for DMX Demultiplexer
eight DMX channels for eight relays
Published in issue 308, March 2002
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).
Resistors:
R1-R8 = 1kΩ
Capacitors:
C1,C2 = 33nF
C3 = 100nF
C4 = 10µF 25V
Semiconductors:
D1-D8 = high-efficiency LED
D9-D16 = 1N4148*
IC1 = 74HCT164
IC2 = 74HCT573
IC3 = ULN2803
IC4 = 7812
IC5 = 7805
Miscellaneous:
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 Ω) (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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Click below to download a PDF copy of this article from Elektor magazine. Please note. In view of the complexity of international markets, Elektor cannot guarantee the availability of components for this project.
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