vibrant lamp

Vibrant LampInteractive Prototype Design---- Lamp DesignBrandon Smith + Kaicong Wu + Heather Culbertson + Jonus Cleveland

The motivation for our lamp came from a simple lamp consisting of an array of LEDs like the one below. We were intrigued by its simplistic design and uniform pattern. We decided to redesign this lamp starting with the basic LED pattern and expanding the lamp to include motion and a method to change the pattern of displayed light. We came up with the idea to shine the LEDs through water

Group Work

Vibrant Lamp || Interacitve Prototype DesignPenndeisgn_Spring, 2011Tutor: Mark Yim + Sanmen Kim

Student: Brandon Smith + Kaicong Wu + Heather Culbertson + Jonus Cleveland


and using motion to disturb the surface of the water. The premise was that this would in turn change the refraction pattern of the light. We first thought to use a circular motion to move the water. We designed a large disk attached to a shaft which would be turned by a motor as seen below. Centripetal force would vary the pattern of the water based on the speed of rotation.


We built an initial prototype that was not actuated but could be manually rotated. From this we found that our initial design would not provide the desired behavior of the water so we decided to go in a completely different direction.Our next idea was to use a speaker to excite water in order to change the

refraction patterns of light. To determine the frequency which would result in the greatest reaction from the water (the natural frequency of our system), we attached the speaker to a function generator and stretched plastic wrap over the top of the speaker. We then sent a square wave into the speaker and varied the frequency until we reached the natural frequency as determined by the greatest reaction from the water. From our tests, this was determined to be around 150Hz.


Next, we designed a circuit to produce a 150Hz square wave to send to the speaker. We used an LM555 timer wired in astable mode.

The LM555 timer is not capable to supplying enough current to the speaker to achieve the desired reaction from the water. Therefore, a speaker driver circuit was necessary to increase the power sent to the speaker. We started with a commercially made 5W power audio amplifier chip (LM324). After prototyping this circuit, however, we found that it did not behave as expected and we were unable to We then prototyped and tested the push-pull circuit.


This circuit is capable of both pushing current into and drawing current from the speaker. The signal from the LM555 timer was first sent through two op-amps (LM324) to offset and amplify the signal so that we could achieve a -5V to +5V sine wave centered at 0V. This new signal was then sent through the push-pull circuit to amplify the current. We decided to use this push-pull circuit in our final lamp design and drew up the circuit in Eagle so we could get a PCB made. Since this circuit requires relatively low input voltage (-9V and +9V), it was easy to power using commercially available AC-to-DC power converters. This voltage was then sent through a 5V regulator (LM7805) to achieve the required input voltage for the timer and offset op-amp.


One we were able to get the circuit working properly, we were free to make several design iterations with different ideas about the configuration of the lamp, speaker, and LEDs. The first iteration used multiple speaker-disk combinations on several pivots.


We decided that given certain constraints, this multiple design would be unfeasible. Therefore we decided to go with a single speaker on a pivot. We added servo tappers to tilt the water tray. This would allow us to change the pattern of water when the speaker was off.


FINAL IMAGE

vibrant lamp

Documents

simple lamp

speaker driver circuit

initial prototype

initial design

simplistic design

natural frequency

lm555 timer

uniform pattern