Chasing Illuminated Staircase: Difference between revisions
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==The Control Circuit== | ==The Control Circuit== | ||
A circuit had to be designed to allow the 0-10volt [[analogue control signal]] to power the relays that would turn each step's lamps on and off. The signal from the demultiplexer did not provide enough current to drive the relay coil, nor enough to drive a transistor. Therefore, the signal from the multiplexer had to be stepped up in two stages. First it was passed through a 4011 NAND gate, then through a transistor & finally passed over the coil of the relay. | A circuit had to be designed to allow the 0-10volt [[analogue control signal]] to power the relays that would turn each step's lamps on and off. The signal from the demultiplexer did not provide enough current to drive the relay coil, nor enough to drive a transistor. Therefore, the signal from the multiplexer had to be stepped up in two stages. First it was passed through a [[4011 NAND gate]], then through a transistor & finally passed over the coil of the relay. | ||
[[Image:StaircaseIndividualCircuit.jpg]] | [[Image:StaircaseIndividualCircuit.jpg]] | ||
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). The output from the logic gate had enough current to drive the base of the transistor. | 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). 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 | ||
