Let's talk about the cash monies.

Big Purchases = Big Impact

Our biggest purchases were also the most important parts of our project. We invested over $40 for an Arduino Mega because each of our 12 servos needed to be controlled from a PWM port. The Arduino Uno that we had been using had only 6 PWM pins while our new Mega had 14. We also spent over $75 on purchasing our servos. We intially bought only as many servos as we needed (12), but when two of them became non-functional without any discernable cause, we decided to buy backup servos in case any more problems arose. Our final large purchase was the black acrylic material that we laser cut our paddles out of. We had originally cut our paddles on the ShopBot out of material that we had found on campus. However, this material was scratched and the paddles were not ideal. Purchasing new material that we hand picked ourselves allowed us to get the shiny, slightly reflective finish that we imagined for the paddles.

On Campus Resources

We are very fortunate to have free and open access to all of the materials and tools on campus at Olin. We hadn't realized how much we relied on Olin's resources until we tallied up all of the costs of the "Free for Us" materials. In addition to helping us offset our financial costs, having the materials that we used on hand allowed us to prototype more rapidly. Instead of having to spec an item, buy it online, and wait for the package to arrive, we were able to find a part, or even an inspiration for a new idea, by poking around the POE lab or ECE stockroom.

Out of Pocket Costs

After spending all but 86¢ of our class budget, we realized that we did not have a way to mount Janis on the wall in the library, where she would be put on display. Since the idea of having Janis stay in the library was a relatively new idea, the cost of the French cleat for mouting was an unexpected expense. However, our team decided that we would be comfortable spending the extra money out of our own pockets in order to help our project come to completion.

Purchased Using Our Class Budget1
Date Purchased Vendor Item Price
 11/02/2015  Amazon  Elastic thread  $5.99
 11/03/2015  Amazon  5V 10A power supply  $11.99
 11/13/2015  Hobby King  HexTronik HXT900 Micro Servos (x12)  $52.90
 11/13/2015  Amazon  Arduino Mega  $43.81
 11/15/2015  Amazon  LED light strip and USB power attachment  $13.92
 11/15/2015  Amazon  Brackets (x10)  $4.48
 11/15/2015  Amazon  Ultrasonic sensors (x5)  $8.69
 11/17/2015  Michaels Craft Store  Wooden dowels (x4)  $2.51
 12/04/2015  Hobby King  More HexTronik HXT900 Micro Servos (x6)  $24.902
 12/09/2015  Altec Plastics  18"x36" sheet of black acyllic (x2)  $79.95
Class Budget Subtotal   $249.14
Extra Team Spending3
 12/11/2015  Amazon  French cleat  $14.97
Extra Team Spending Subtotal   $14.97
Free for Us4
Item Notes Price
 Infrared (IR) sensors (x6)  From POE lab, $8.75 each, priced on DigiKey, $8.75 x 6 = $52.50  $52.50
 3-pin sensor connectors for IR sensors (x6)  From POE lab, $0.99 each, priced on Pololu, $0.99 x 6 = $5.94  $5.94
 ¼-20 2" black oxide hex-head bolts (x8)  From MechE cart in the POE lab, $0.28 each, priced on Fastenal, $0.28 x 8 = $2.24  $2.24
 ¼-20 lock nuts (x8)  From MechE cart in the POE lab, $0.07 each, priced on Fastenal, $0.07 x 8 = $0.56  $0.56
 ¼-20 2" machine screws (x4)  From MechE cart in the POE lab, $1.39 each, priced on Grainger, $1.39 x 4 = $5.56  $5.56
 Behr Lump of Coal Flat/Matte Interior Paint  From library, $31.98/gallon, priced on Home Depot  $31.98
 3/4 in. x 4 ft. x 8 ft. plywood  From ShopBot area, $49.98, priced on Home Depot  $49.98
 3D printing filament (128.28 grams)  From 3D printing area in the library, $0.035/gram, cost based on Olin estimate, $0.035 x 128.28 = $4.49  $4.49
 Protoboard  From ECE stockroom, $6.72, priced on DigiKey  $6.72
Free for Us Subtotal   $159.97
Project Total: $424.08

1. Each team was given a budget from the class of $250.
2. On the reimbursement form, the price of the servos was mistakenly recorded as $24.09 instead of $24.90. Therefore, there is a 81¢ difference between the reimbursement amounts and the amount we actually spent.
3. After we spent our in class budget, any extra purchases were out of our own pockets.
4. This applies to supplies that we found in the POE room or aquired elsewhere on campus. The costs are an estimate of what we would have paid if we purchased the materials on our own.