Applications and Implications

Assignment

Start thinking about your final project and answer these questions:

1. What will it do? ✅
2. Who’s done what beforehand? ✅
3. What will you design? ✅
4. What materials and components will be used? ✅
5. Where will it come from? ✅
6. How much will they cost? ✅
7. What parts and systems will be made? ✅
8. What processes will be used? ✅
9. What questions need to be answered? ✅
10. How will it be evaluated? ✅

Final Project

What will it do?

It will sort coins, keep track of their values, and dispense coins to pay for everyday purchases.

Who’s done what beforehand?

See the References and Inspiration section below

What will you design?

I am planning on taking some existing designs and building on top of them to add more features.

The existing designs have some good features but could be improved by:

• Coin sorting
  • Eliminating manual operation of the crank
  • Auto-detecting which coins are being dropped in
• Tracking
  • Keeping up tally of how much money is in the piggy bank.
  • Displaying the total amount of money to the user.
• Coin dispensing
  • Automatically dispense the correct amount of coins up to the desired amount
  • Provide easy to use 1-click buttons for common everyday expenses

What materials and components will be used?

See iterative design section below to see which materials will be required by each iteration.

If we were to assume ideal circumstances (all iterations completed), these would be the bill of materials

• Main Body
  • 3D printed and Acrylic
• Electronics
  • 2 or 3 Atmel SAMD11C/21D Microprocessor(s): enough to control all the components.
  • 8 x Servo motor(s) to dispense each type of coin
  • 8 x Infrared LED and
  • 8 x Infrared sensors, to detect presence of coins
  • 1 x stepper motor, to automate the spinning of the top plate

Where will they come from?

• MDF boards
  • Purchased at Servei Estació, a local retailer
• PLA for 3D printing
  • Purchased at 3DJake, a local retailer
• Servos
  • From the local lab
• R.Pi Touchscreen and Coin acceptor
  • Purchased at Sparkfun

How much will they cost?

About a ~100 Eur

What parts and systems will be made?

Components:

• Coin intake:
  • A funnel for all types of coins to be dropped in (unsorted).
  • Circular coin dispenser that will rotate to move all the coins across the dispatching surface
• Coin sorting:
  • will have different sized holes (one for each type of coin, ordered from smaller to larger, starting from the first one)
  • the different sizes of holes will allow only 1 type of coin to fall through. The smaller ones will have fallen in previous holes, and the larger ones will not fit and will be carried forward to the following holes
• Coin Counting
  • Each holding cylinder will have a sensor that will detect when a new coin has been dropped in.
• Stateful coin tracking:
  • The system will keep tally of how many coins are inside.
  • It will also display the current amount to the end user.
• Coin dispensing
  • Each cylinder will have a dispensing mechanism that will be controlled by a microcontroller and actuated by a servo.
• Coin presentation
  • All the dispensed coins will be collected into a presentation tray where the user will be able to pick them up.

What processes will be used?

• 2D/3D Design
  • Case
  • Coin ejectors
  • Coin Ramps
  • Integration panels for commercial parts
• 3D printing
  • Coin ejectors
  • Coin collector funnels
  • Servo Holder
  • Pinion and Rack
• Laser Cutting
  • Case
  • Coin ramps
  • Integration panels for commercial parts
• Maybe molding/casting (to improve texture)
  • Interface buttons (unless I go for touchscreen)
• Electronics production
  • Main board for the microcontroller
  • Servo controller board
• Electronics programming
  • Main board for microcontroller

Features

• User input:
  • Users will be able to use 1-click buttons to request common amounts for everyday purchases
• Coin tracking:
  • Incoming coins increment counters
  • Dispensed coins decrement counters
• Coin dispensing:
  • The system will calculate how many coins of each type need to be dispensed in order to deliver the right amount of money, and it will use servo motors to eject the right type of coins.

What questions need to be answered?

• Where to find all the required material?
  • What can the lab provide?
  • Where can we purchase electronic components / recommended providers?

How will it be evaluated?

See iterative design section below.

Probably, iteration 4

Iterative Design

☝🏻🙂💡 These are temporary goals, for the real iterations (and adaptations to the real world), check out the project management page

Iteration 1 - MVP: 3 coin dispenser

A manually operated box that can sort 3 different coins and dispense them, on command, via button/serial input.

In scope

• It can sort each coins into the correct slot
• It can dispense coin of the right type, on command

Out of scope

• This will not count coins
• the coin ingestion crank will be manually actuated
• no checking/verification will be made, if a slot is empty, it will still try to dispense coins (and it will believe it succeeded)

This will help me understand any hidden angles or blind spots I might have missed, and adapt accordingly.

Iteration 2: Adding coin detection sensors

This will be like iteration 1, but with infrared sensors to detect when a coin goes into each of the slots

Iteration 3: 8 coin holder

Same as Iteration 2 but with 8 holders instead of 3, so it supports all Euro coin sizes.

If there were supply shortages, this might be reduced to 5 holders instead of 8, and the machine might be adjusted to reject smaller denominations coins (via separate tray)

Iteration 4: Adding user-friendly buttons

In iteration 4 we will add user-friendly buttons for 1-click operations (e.g. press button 1 to receive 2.45 Eur for bread, press button 2 to receive 1.90 Eur for the bus, etc…)

Iteration 5: Displaying total money stored

In iteration 5 we will add a small display to show the user how much money they have saved.

Iteration 6: Future improvements

In the unlikely case that I have time to spare, I would like to introduce the following nice-to-have features:

• Smart algorithm for coin dispatching:
  • Is it better to dispatch two 1 Euro coin or one 2 Euro coin? if we have few coins left?
  • Is it better to dispense 1.50 as 3 x 0.50 or as (7 x 0.20 + 1 x 0.10 )? What if there is no choice and we have to dispense 15 x 0.10Eur?
• Stateful machine / Battery powered
  • This would allow the machine to be turned off to save power
  • It would require the machine to support power-saving mode, or to store the current amount of money into EEPROM, so it survives restarts and power outages.

References and Inspiration

There seem to be 3 major categories of coin sorters in existence:

• Layered coin sorter
• Tilted ramp coin sorter
• Concentric coin sorter

Layered coin sorter

These coin sorters work by having distinct layers with holes of different sizes.

While the design is simple, the amount of work needed to automate this might be too much, as it requires random shaking in 3

Tilted ramp coin sorter

These coin sorters generally require lots of horizontal space, and need a feeding mechanism that ensures that the machine does not encounter mechanical problems (getting jammed, taking more than one coin at a time through its sorting ramp, etc…)

Concentric coin sorter

This design uses the same principles as the previous type but has several differences.

PROS:

• Same principles and function
• More compact: smaller size
• More efficient: 1 spin of the wheel can carry 6 x more coins.

CONS:

• More compact: components are more crammed. Making changes to the design will also be slightly more complex
• More efficient: the motor needed to spin the dispatching wheel will need to have enough power to rotate it, even if all the slots are full
• Coin dispensing will need to be carefully designed to make sure components don’t collide with each other.

Commercial products

• Counting 25 Gallons of Coins at 10,000 Coins per min!
• SparkFun Coin Acceptor.
  • Interesting
  • Slow (1 coin at a time)
  • Useful to count values of coins but not what we need.
    • We need to classify coins. Counting values is a nice byproduct we’ll get once coin classification works properly.

Non-commercial designs

Family tree of inspiring designs:

• A compact coin separator with manual actuation for Brazilian Reais instead of Euro.
  • Which is a remix of another coin separator
    • Which is, in turn, another remix of a different coin separator for Euro coins, designed by a 12-year-old
      • Which was inspired by a coin separator for US Coins
• A coin detector that uses infrared LEDs and sensors to notice when a coin drops into each sector.