Light Up Device Design Challenge

Assignment

This assignment is a design challenge that will be introduced in class, and then you will continue independently to complete it this week, following the instructions below. The recommended amount of reasonable time to spend on this challenge is ~6 hours max. At the end of the assignment, you will have a prototype of your solution, and an Engineering Notebook documenting specific "deliverable" items you are responsible for generating along the way as you progress from one step of the design process to the next. During the design process, you may generate hand-written notes, typed text, hand-drawings, CAD drawings, photos, images or screen captures, etc. All of these items should be embedded into a digital document format of your choosing and submitted as a link on CANVAS (Jamboard, Google Slides, Google Doc, etc.), and then posted to your Digital Course Portfolio by Week 8.

Brainstorming

The morph chart was feeling a little restrictive for me with this project, so instead, I used Jamboard. I just created sticky notes, rapid-fire, of anything that came into my head. Then I reviewed them and came up with 5 categories that they seemed to naturally fell into. I sorted the notes into those categories and made my primary and secondary selections from them. The Jamboard is available here if you want to see the selections more clearly.

I decided upon making an "On Air" sign for the door of my office. My office in a busy part of the house and often my family will walk in to get to the laundry room or let the dog out into the backyard. This is really disruptive during Zoom meetings or classes. A flashing sign that I can turn on and leave on as needed will remind them not to enter. Using upcycled containers from take-out gives me the ability to make multiple signs, so my husband can have on for the bedroom (where he works all day) and my kids can have signs as well.

Design Brief

Background: As my business and teaching have moved more and more online, I have found that much of my time is spent online in Zoom meetings, attending classes, or filming videos. Being disrupted by a family member with a laundry basket of underwear is really embarrassing when meeting with a new client, so it has become clear that I need a way to signal to my family during those times that I need my office door to stay closed and the noise in the kitchen to stay relatively low. However, I don't want to spend a fortune on such a sign. Using a plastic container from take-out leftovers, some spray paint, and a few LEDs with a switch will make it easy for me to alert my family when mom is working. In addition to accomplishing that goal, I'm also diverting waste from the landfill, cleaning out the infamous "Tupperware drawer," and making an item that will be easy to reproduce for other work-at-home moms or my husband.

Requirements:

• Turns on and off with a switch.

• Balances form and function.

• Uses at least 3 LEDs and a parallel circuit.

• Battery pack is hidden but accessible.

• Switch is remote from the sign, allowing the sign to be turned on from inside the office.

• Lightweight enough to hang above a door with minimal hardware.

• Easy to hang and take down when batteries need replacement.

• Creates enough of a visual that the warning can't be missed, even if the hallway light is on.

Constraints:

• AA batteries

• ~ 6 hours of beginning to the end of the design process

• Upcycled take-out containers as base

• Spray paints and acrylic paints available in the house

• Blinking LEDs leftover from Maker Camp for flashing affect

• Conductive Makers Tape from previous projects to make a quick circuit

• Scrap wire and from past projects to wire the switch

• Craft vinyl and the Silhouette vinyl cutter and software

Research

I researched Google images to see how commercial "On Air" signs looked. Most had a dark background, often black or red, with bold white letters. I decided to use red both for the front plate cover and for the lights to maximize impact.

I opted to use a black take-out container rather than white, because the white was more translucent. More of the light inside the sign bled with the white container and I didn't get as bold a result on the front of the container with the white as I did with the black container. I did decide to paint the inside of the container with glossy white spray paint to maximize the reflective properties inside, in hopes of brightening the effect on the front of the sign.

I tested my circuit using the battery pack and some alligator clips. I wanted to make sure that the red blinking LEDs were able to be powered with the AA batteries and didn't need a resistor. I tested 3, 4, and 5 LEDs to see who lit the sign well. In the end, I found that 3 LEDs lit the sign well, did not need a resistor, and were easily powered by the batteries.

Below is my Tinkercad model of the circuit.

Planning

I sketched the front and inside of the sign in my Engineering Notebook. As I took measurements of the take-out container it was clear that the curved, faceted shape of the container would limit the area I had for both the circuit and the test on the front. Taking careful measurements really helped when it came time to make my prototype, because everything fit as I planned.

I also measured the distance from the top of my door to the inside wall where I wanted to place the switch. It required more wire than I'd originally planned. That meant I had to hunt for additional supplies. Luckily I keep a roll of wire on hand for exactly this reason.

I also had to think about the best placement for the battery pack. I decided to place it on top of the sign, so it would be hidden, and centered so that the sign wouldn't tilt. I wanted the battery pack to be on the outside of the sign, so that I wouldn't have to open it, risking disturbing the circuit, when I wanted to replace the batteries. The downside of this position is that the batteries would then be difficult to access above the door. So I planned holes in the back of the sign that would make it easy to hang the signal and take it down when needed.

Planning the front of the sign was a bit of a challenge. I didn't want to use vinyl for the final lettering, as the light did not sign through the vinyl well. Also the top of the take-out container was clear, and the light ended up looking more like pinpoints. It was unattractive and harsh. I wanted to diffuse the light, but not block it. I designed to spray the inside of the top white a light coat of white spray paint. Then I planned to cut vinyl letters for the front, apply them, and spray paint with red, allowing the vinyl to mask areas so that the words would be left in white when the vinyl was removed. I planned this in my Silhouette Studio design software (below).

Prototyping

My plan for the front of the sign went a bit awry when I left the spray paint to dry for too long before removing the vinyl. As a result, so of the paint stuck to the vinyl and lifted or tore. So I had to touch up the lettering with glossy acrylic paint. Then I gave it a clear coat to look more consistent. For the next one, I will make sure I remove the vinyl letters right away or I will prime the front, mask with vinyl, and use acrylic paint so that I have more time to remove the letters.

For the inside of the sign, I used Maker Tape, which is conductive fabric adhesive tape used often in paper circuits and wearable electronics. I love it because it makes prototyping circuits really fast. However, it had some trouble sticking to the painted plastic. It took a bit more effort than expected to get everything attached well. One LED in particular wasn't sitting right and refused to light up. For the next one, I will instead use wire and hot glue it all to the inside or use a small breadboard.

The switch presented a few problems. I had a tough time getting a good connection between the battery pack wire and my insulated wire using a wire nut. It kept coming loose while I was hanging the sign and placing the switch. Next time I'll just solder the connection. I mounted the switch onto cardboard and attached the wire, but I should not have mounted the switch to cardboard until AFTER I'd passed the wires through the gap in the door frame. Instead, I had to run it along the inside of the frame. Luckily the wire is thin and there was plenty of clearance. I test a few ways to hang the switch on the wall. I added additional cardboard and nano tape so that it stuck to the wall but could be easily moved.

Testing

After hanging the sign above my door, I ran the switch to the desired location and tested that it turned on properly. It did after some adjustment to the wire nut connection. I had my husband stand in the hallway and observe the sign in action with the hallway light on and off. In both cases, he saw the flashing light clearly. from the end of the 10 foot hallway.

I did not mention the addition of the sign when my kids came home from school. Both immediately noticed it, even when off. They also tested it with the hallway .light on and off and said that it was clear when the sign was active. My youngest asked for one that says, "Go Away!" for her room.

For some reason, the flashing of the sign starts coordinated, but soon one LED flashed off rhythm. I suspect it is the one I was having trouble getting to light initially. I'll need to check that connection and fix it, but for now, it's meeting my needs.

I'll be monitoring hours used against battery replacement so that I can get an idea of how long the batteries will last over time. I may want to move to a rechargeable option if the batteries don't last long. There isn't much point in upcycling materials and using leftovers in the construction of the sign if I'll be wasting lots of batteries while using it.

Redesign

Items I'd like to redesign:

• Use wire and solder to make a better connection between the LEDs and other circuit components for more reliable performance.

• Consider using wood or plastic to make the back of the sign more sturdy. The flex of the plastic may be the reason that LEDs are not staying as connected as I'd like.

• Consider moving the battery pack inside of the sign, so that only the front needs to be opened, rather than taking down the sign to replace batteries. This would also allow the connection between the switch and battery pack to be soldered and glued into the sign so it moves less, hopefully limiting the connection issues I'm having.

• Change the way I make the front of the sign so that I don't need to do as much touchup. At the very least, set a timer, so I don't forget to remove the vinyl.