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Electronic box of tricks to perform the switching... This is the sequential switcher unit itsself. Based around a modified Vellemann "Programmable Running Light" kit, it is essentially a shift register chip clocked by a simple variable speed 555 timer circuit (which has an external speed control pot and blinking LED so the switching rate can be easilly set). When activated (normally by the main timer), the control relay sets the input to the shift-register high, and the 8 outputs subsequently go high one by one as it gets clocked by the 555. These outputs feed the coils of the six blue relays via transistors, with the last two of the eight outputs not used. The output contacts of the blue relays switch 24 volts out to the 110 volt control relays within the main panel, and to DIN sockets for connecting to external relays in remote equipment. At the end of the night when the lights are turned off, the original control relay is de-activated which sets the input of the shift register low, and in turn the outputs also go low, de-energising the relays and turning the lights off. The switcher circuit is always running, watching for a change of state of the input coming from the control relay.
The control relay is activated by two means, selected with a front "run mode" toggle switch. Ordinarilly it takes its switch-on cue from the control panel`s timer, via a variable delay switch. When the timer turns on it immediately energises the main power contactor feeding the 110 volt transformers. The delay switch is usually set to activate the sequential switcher`s control relay after about 30 seconds in order for things to stabilise and prevent switch-on surges. When the timer switches off, the sequential switcher`s control relay turns off immediately, but a delay-off switch prevents the main contactor from dropping out right away, giving the lights time to turn off in stages. After about twenty seconds, the contactor drops out, shutting the power off. The other activation method for the sequential switcher`s control relay is with a latching "button start" circuit, within the sequential controller. This is for the "Grand Switch-on Button" used to start the display at the beginning of the season. The button unit hooks up to the controller via a long 6-core cord terminating in a DIN plug that goes to a socket on the front of the panel. When set to "button" by the "run mode" switch (after the main power has been turned on either by the timer or the override switch), a yellow lamp on the front of the button unit lights. Turning on its "arm" key sets a ring of red LEDs around the button flashing instead of the yellow lamp. Pressing the button causes a ring of steady green LEDs to light around it in place of the flashing red ones, and latches a relay inside the controller, activating the sequential switcher control relay and switching on the lights in six stages. The button may then be unhooked and the controller switched back to timer mode without the lights turning off. There is a "reset" button next to the start-button`s socket that un-latches the relay should it need to be manually switched off, for example following a test of the system earlier in the day. |
