Chasing Illuminated Staircase: Difference between revisions
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Passing the signal from the demultiplexer through the 4011 logic gate gave the advantage of a clean on/off signal going to the transistor (the channels used for the stairs on the lighting desk were also set to non-dim). A 0 to '''+10''' volt demultiplexer was used, as oppopsed to the more common 0 to -10 volt, which allowed the demultiplexer signal to drive the 4011 inputs. 4011 chips were used because they were available in house. The output from the logic gate had enough current to drive the base of the transistor. However, as the input signal passed through the NAND gate it was inverted - i.e. the output from the NAND was high when the input was low and vice versa. Because of this a PNP transistor was used. The PNP transistor activates when the base voltage drops. The output from the transistor had enough current to drive the coil of the relay. | Passing the signal from the demultiplexer through the 4011 logic gate gave the advantage of a clean on/off signal going to the transistor (the channels used for the stairs on the lighting desk were also set to non-dim). A 0 to '''+10''' volt demultiplexer was used, as oppopsed to the more common 0 to -10 volt, which allowed the demultiplexer signal to drive the 4011 inputs. 4011 chips were used because they were available in house. The output from the logic gate had enough current to drive the base of the transistor. However, as the input signal passed through the NAND gate it was inverted - i.e. the output from the NAND was high when the input was low and vice versa. Because of this a PNP transistor was used. The PNP transistor activates when the base voltage drops. The output from the transistor had enough current to drive the coil of the relay. | ||
9 volt power was supplied from a normal domestic mains transformer, which could output upto 450mA. 12 power for the transistors and lamps was provided from a car emergency jump-starter. The jump-starter was placed inside the staircase and was trickle charged during rehearsals and between performances. This meant that only a single 13A extension cable and a single control cable were run to the staircase. | |||
==Construction== | ==Construction== | ||
The staircase had 15 steps, so the circuit above was replicated to include 15 resistor/transistor/relay sets. As each 4011 chip contains 4 logic gates, only 4 chips were needed. | The staircase had 15 steps, so the circuit above was replicated to include 15 resistor/transistor/relay sets. As each 4011 chip contains 4 logic gates, only 4 chips were needed. | ||
