NOT FINISHED YET -- need to update the webscrapper to get the currencies.


Coin Counter is an easy-to-use Android application that can count how much money there is in coins, using the smartphone camera. It also provides a currency-convert calculator.


This application was designed to make the tedious task of counting coins quicker and less tiring, especially for small commerce, who always receive a lot of them from their clients. It also intends to help small business owners and costumers not to touch in coins as a measure of preventing the spread of COVID-19. Initially, our machine learning model was projected to achieve its task in a raspberry pie 3, ideally stopped at a determined position with a dark background allowing better recognition, but due to a loss of hardware we opted to implement it in an Android application which is also a good fit for this model.

What it does

It uses the smartphone camera to identify the value of each coin in an image and displays the sum of them. It also has a currency-convert calculator, where you can fill an amount and an exchange rate, and it returns the conversion result.

How we built it

Using the Android Studio API, as well as Pytorch and OpenCV.

Machine Learning

We trained a Convolutional Neural Network model called MobileNetV2, which we download from the Torchvision Python package. This model is more suitable for use in mobile devices, as it optimizes the number of floating-point operations needed for inference. To train this model, we created a dataset from scratch (link: and labeled all images using the software Colabeler (Link:

Precision Recal
0.98 0.98
0.95 0.97
0.97 0.98
0.98 0.97
1.00 0.98

Confusion Matrix:
[49. 0. 1. 0. 0.]
[ 1. 58. 0. 1. 0.]
[ 0. 1. 65. 0. 0.]
[ 0. 2. 0. 63. 0.]
[ 0. 0. 1. 0. 58.]

How to use this application

Once you access the app, you can choose to use the counter or the currency converter. If you choose the counter, you must point your smartphone's camera at the coins, which must be on a flat, opaque surface, and then you can view the count value. If you choose the converter, you must inform the quantity and the exchange rate, and then you can view the converted value.

Challenges we ran into

We have almost no experience in programming in java and XML, and it's the first time we made an application that uses the android camera, pytorch_android and OpenCV for Android.

What we learned

We learned significant aspects of the Java language, as well as how to perform image morphology with OpenCV for Android and how to translate a PyTorch model to Android.

What's next for My Coin Counter

For now, this application only supports the Brazilian currency ("R$"), but it can be improved to support other currencies as well. Also, it will be useful to get the exchange rate between coins from the internet rather than ask the user to fill it.

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