Relay Extension for DMX Demultiplexer

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).