Retractable Holiday Lighting System Group 17 Travis Tate and Brittany Potter
Introduction • Finding time and energy to put up and take down holiday lights can be tough. • Nobody likes to look at holiday lights still hanging a month after the holiday. • A retractable holiday lighting system with low visibility parts when the lights are retracted solves both of these problems
Objectives • Only have to put up lights once instead of every year • Quickly and safely deploys lights once installed, eliminating need to climb ladders • Low visibility means its not an eyesore and blends in with the home’s exterior • Dusk/Dawn sensor that turns lights on at night and off in the morning
Switches and Debouncing • Extend/Retract Switch – The switch being in the high position ( i.e. 'ON' ) indicates that the user wants to Extend the lights. Low ( 'OFF' ) indicates the user wants to Retract the lights. This signal is then used to control whether a positive or negative voltage is sent to the DC motor, thus controlling the direction in which the motor runs. • Light Switch – In the high position ( 'ON' ), the switch will force the lights to be on, regardless of the status of the Dusk to Dawn Sensor and Switch. The low position ( 'OFF' ) yields lighting control to the Dusk to Dawn Sensor and Switch. • Dusk to Dawn Switch –If the Dusk to Dawn Switch is high ( 'ON' ) and the Dusk to Dawn sensor indicates it is night, the lights will be turned on.
Sensors • Stop Signal – The two ends of the string of lights attached to the holiday tracked will be marked with reflective material. A sensor generates a signal when it “sees” these markers. As the track is being extended/retracted, the first marker is to be ignored since its the far end of the lights that is wanted. A toggle flip – flop ( JK wired to be a toggle ) indicates when the second marker is reached. The motor should then cease operation. • Stop Sensor – A photodiode is used to detect reflected light at the opening where the light track enters the motor housing. The surface beneath the photodiode is black and the lights pass over this surface. This photodiode is being compared to a photodiode that is always exposed to a black surface. When the white marker at the end of the lights passes under the sensor photodiode, the amount of reflected light should increase resulting the comparator to output a logic value of ‘1’. Otherwise, the output is a logic value of ‘0’. Because of the highly sensitive nature of the photodiodes and the effects of ambient light, this voltage is then debounced using a simple SR latch before being fed into the rest of the circuit. • Dusk to Dawn Sensor - A photodiode is used to detect ambient light in order to determine whether its day or night. It is compared to a photodiode that has its photoeye covered. The comparator will then output a logic value of ‘0’ when the sensor diode’s voltage is equal to or lesser than the covered diode’s voltage ( i.e. it is dark outside ). Otherwise, the output is a logic value of ‘1’.
Logic Diagram • Simple logic is performed on the signals from the Dusk to Dawn Sensor, the Dusk to Dawn Switch and the Light Switch. The output is to be a logic value of ‘1’ if the Light Switch is ‘ON’ or if the Dusk to Dawn Switch is ‘ON’ and the Dusk to Dawn Sensor indicates it is night ( i.e. its value is ‘0’ ). This generates the Lights Control Signal. • DC DC converters are used to step – up the control voltages for the two 12VDC relays from 5V to 12V. • The Lights Control Signal feeds into a 120 VAC SPDT Relay with a 5 VDC control input. The output of this relay is the power going to the outlet that the holiday lights will plug into. • The Stop Signal from the Sensors Subsystem and the signal from the Extend/Retract Switch are fed into two cascading 12 VDC relays. • The Stop Signal is used as the control signal on the first relay, an SPDT relay wired with +12 VDC and 0 VDC as its two possible choices. This ensures the 0 VDC will be sent to the motor when it is supposed to be stopped. The output of the SPDT relay is then fed into the choices of a DPDT relay. • The DPDT relay is wired in such a way that it will either output a positive or negative version of the output voltage of the SPDT relay. The DPDT relay is controlled by the signal from the Extend/Retract Switch. Positive voltage out corresponds to extend while negative voltage out corresponds to retract. The output of the DPDT relay is then used as the power going to the motor.
Design Issues • Photodiodes have low voltage output. • Comparator circuit • Photodiodes are highly sensitive to changes in light. • Debouncing stop signal • Placement • ‘0’ level photodiodes for comparison • Relay control voltages
Initial Track Designs Both designs use a motorized pulley system that would allow the light carriers to go down and around the end pulley. Fishing line, rope, or rubber band were all possible choices to be used as pulley cable.
Initial Track Designs Track with cart that carries the lights. Rope or rubber band would be used for this configuration.
Initial Track Designs • This design would have used no carriers and fishing line was the main possibility for the pulley cable. • The lights attached to the cable directly and would have been wrapped around a spool in the motor housing. • Initially this design was used but testing, showed its major flaws: • The lights wound and unwound faster than the fishing line from the spool • The plug-in for the lights would wind around itself with each revolution • There was not a good way to attach a big enough spool to our motor
Final Track Design Schematic from website of Tru-Roll The carts could be bought separately and the track made but it would be best just to buy the track that was made for them. Rope and rubber band was tested with this design but the carts did not roll well enough to be used.
Demo Track • Graber 2-way traverse rod from Lowes • This was used for the demo. • Rope with it was tested first but it was too tough to get it tight enough to pull it. • Rubber band that came with pulley used with motor worked excellent and allowed for extension and contraction of the rod.
Inside Motor Housing Housing is made of plywood because it would be easier to decorate however the owner wants it. It might be more commercially viable to make it out of plastic.
Control Circuit Placement The three switches for the lights, dusk to dawn control and motor control can be place wherever the owner wants them. They will be connected to the control circuit which is inside the motor housing. This is different than our original block diagram where the control box and motor housing were separate.
Recommendations • Make the motor and lights controls wireless to replace or in addition to the switches • Tracks with bends in them for fitting around buildings. • Dusk to Dawn motor control as well as the lights (Tony’s idea) • Motor speed control