Cash register that can tally the amount of cash in it

1. 1. Introduction
Accounting for money is an important component in business management. In the retail
industry, this is especially the case when dealing with large amount of inventories. Big
corporations like Wal-Mart and Fairprice use the point of sale system (POS) for their
transactions. Taking this concept, the project aims to develop a small POS system that acts as
an electronic cash register and money counter that accounts for the sales of the day by
calculating the amount of money (coins and notes) inside the cash register using sensors.
This system will be helpful for small and medium enterprises as it will be cheaper and less
complicated than the actual POS system. Our idea is that we can attach a small sensors on the
different compartments of the cash register to record the amount of coins or notes inserted
according to its value assigned on the compartment. Therefore the sum of the money can be
tallied together and matched with the sales.
2. Designing process
We want to design the cash register as physically close to the cash register that is on the
market today. We also consider the money counter and coin sorter design to incorporate into
our design. After brainstorming and discussions, we have encountered a few problems.
1. The type of sensors suitable. Coins and notes require different techniques of sensing
2. Algorithm and codes for calculation. The software component of the system.
3. Integration of the program and the cash register to a computer, finding a suitable
interface chip
For this project, we make a simulation of the process using a box with buttons to
represent the different compartments of the cash register. There are 7 compartments during
the simulation. 5 are buttons and 3 are toggle switches. 1 button is used for summing function.
A sensor is connected to the toggle switches to represent that each compartment are
connected by one sensor. The sensor uses will sense the coins. The layout of the simulation is
represented on appendix B
3. Main equipments
1x PhidgetInterfaceKit 8/8/8 $150
Using this interface kit, we can directly convert the sensing which is analog counting
convert to digital signal that can be read by the computer. Also its major advantage is it
can be connected directly to the computer using a USB port.
3x Toggle switches $1-2 per piece
5x Switches $1-2 per piece
For the simulation of sensing the coins and notes

2. 1x Proximity sensor around $20
For sensing coins.
4. Hardware
As mention early, the box that we created act as a simulation for the actual product. The
reason we choose the phiget interface kit is that converting analog to digital signal require a
complex electronics configuration to implement. Thus by using the interface kit, we can
make use of this available technology to allow direct connection. This way, it saves both
money and increase efficiency of the whole system without creating a complex structure.
The placement of the sensors is determined after the considerations of the coin sorter
machine structure. As the coin sorter differentiate coins through mechanical spinning of a
disk and sorting by the size of the coin. A hole is made to allow the different size of coin to
enter into its individual compartment.
Therefore by placing sensors at the side of the opening of different compartment in the
cash register, we can get the amount of coins to be calculated individually.
Placement of A sensor on a coin compartment
The sensor we use is proximity sensor. It works by emitting an electromagnetic field that
detects any object that is within its field. The reason we use proximity sensor is because it is
sensitive and it does not require any physical contact for the sensor to detect the coin. It is quite
cheap and user friendly without any physics background. User just requires knowing the range of
the electromagnetic field. Connection of the sensor is shown below.

3. As it can be seen, there is a need for a ‘common’ ground, to prevent electrical anomalies
and safety.
Improvements to consider
For the notes counting, we require different type of sensor to calculate as notes does not
contain metallic object. We can use maybe a small laser sensor to detect the notes. For coins,
we can make the sensor as small as possible to fit into the cash register maybe into a nano
size sensor. This way we reduce the size and cost of the cash register. The sensor only can
detect one coin at a time. We can form need more sensors to include more coins to be
detected at one time
5. Software
The programming software we use to write the code is Visual C++ which is being taught
in Year 1 computing course. It will provide the ‘skeleton’ of the program and it will be
converted to Visual Basic for a better graphic representation of the program. The code is
shown in appendix A.
Basically it is a simple code that collects the digital signal from the different input of
interface kit which represents the different compartments of the cash register. After the total
function is activated by the total button, the total of each input will be multiply together with
the values that are assigned and then the values will be summed together giving the total
sales of the day.
The most important part of code is that is it simple. The program returns the sum hence it
can be represented with a notation of O(n1+…+nx) as it is the summing of x amount of
functions.
Improvements to consider
The current code only can count by adding the coins. The cashier is required to take out
of all the coins inside the compartment and pour them back again after activating the

4. program. We can rewrite the code to include subtraction to allow the cashier to take in and
out the coins due to the transaction with customer without hassle.
Also we can implement more functions like undo, recount
6. Integration of software and hardware
This process took up the most of the time in this project. We require following the
code provided by phidget allowing the program and the sensor to run together and the
computer need receive the input of the sensor for calculations. This product require
phidget driver to run interface kit. Also the circuit design of the product require proper
configuration.
The interface kit has to be activated by the initialization code that is provided by the
company. The code requires some modifications to apply to our project.
The system works using in active high. It means the signal is initially set to 0. After
the sensor detects a coin, it will transmit a signal and activate the value to 1 to the
different index on the chip, which in turn will be activated by the sensor signal. After
both of them are activated to 1, the program will start the count loop.
7. Marketability
This product will be suited for small and medium enterprise that does not require
the actual POS system as they do not have a large amount of inventories. This product
allow the boss to monitor the daily sales and to prevent workers from stealing as all the
sales will be saved in the computer and tallied at the end of the day.
8. Conclusion
In this project, we have learnt to use an interface kit to integrate the program and
the sensors together to form and counting cash register. We learn and select the suitable
sensor for coin detection. Using the proximity sensor we can sense the amount of coins
inside the compartment in a fast and efficient way.
We write an addition code from scratch using Visual C++ and the knowledge
from the computing course. Additionally, we combine this knowledge with the specific
initialization code provide by phidget company to activate the interface kit to detect the
signals from the sensor. In the end created a system of the cash register.
9. Reference
Inductive proximity sensor
http://www.phidgets.com/products.php?category=1&product_id=3527

5. Programming code; http://www.phidgets.com/programming_resources.php
Appendix A
Appendix B