Week 1 Basic Design

 

Introduction

Mobile phone is now an essential part of our daily lives, it plays an important part in communication, photography, social networking, etc. We have all more or less encountered the situation when the battery of our phone is running low and can not find a place to charge the phone.

The power bank has become popular based on this, our project aims to a deliver solar power phone charging device, i.e, a power bank with solar panels on it. With this, we would be able to extend the usable time of the power bank by charging the power bank whenever there is sunlight or when we forget to charge the power bank before leaving home. Additionally, it is environmentally friendly since solar power is renewable energy.

 

Structure design

The components included in the circuit:

1. Tp4056 chip * 1

2. 3.7V, 10.4Ah Li-ion rechargeable battery pack * 1 

3. Toggle switch * 1

4. 5V solar panel * 2

5. LM2577T-ADJ * 2

6. 5V 1A micro USB charger * 1

7. 1N 5821*1

8. 100uH inductor*1

9. Capacitors that are necessary

10. Resistors, wires that are necessary

 

In week 1, we put up a test for the circuit separately. 

Stephen built up a circuit on the breadboard to test whether the solar panel could provide us with a 5V voltage. For the rechargeable battery pack, Xinyu examined and found that the voltage across the battery back is 3.6V as expected. In addition, Giles worked on the DC booster circuit, hoping to boost the voltage given by the battery pack to the number we desire.

                

                               

We use the flashlight on the phone to simulate the sunlight when conducting the experiment in the lab room. However, we later discover that the voltage produced varies greatly according to the distance between the light and the solar panel. A tp4056 chip was then introduced to reduce the fluctuation of the voltage produced by the solar panel.  More importantly, it could also prevent the battery from being overcharged. 

Another problem reveals when we were testing the circuit after including the chip, the chip became really hot in a short time after we plugged it into the power source. Aiming to solve it, we thought about using a heat sink to help with the cooling process. As well as trying to figure out whether could it be some kind of mistake we made during the construction of the circuit that lead to the overheating of  tp4056.

 

Next week

1. Find out what causes the overheating of tp4056 and exclude the problem.