Hundreds of millions of electric batteries are thrown away every day due to insufficient voltage for use. Although these batteries are low voltage, they still contain a lot of unused energy. Thus, millions of joules are left unused. The idea of the device presented in this article is to try to extract as much energy as possible from these batteries.
Tools and materials: -Toroidal inductors with a ferrite core; -Six bipolar transistors 2N2222; -Six resistors 1 kOhm; -Six diodes Schottky 1N5819;
– Printed circuit board;
-Soldering accessories; -Seven battery holders of different types; -Arduino; -Power switch; -Plastic case; -DC/DC converter; -Display; -Power button with backlight;
Step one: general principle of work
The principle of operation of this device, later called the Joule thief power bank (JTPB), is based on the parallel operation of several Joule thief schemes. The reason for this is that there are many different DC/DC boost converters on the market, but most of them operate at voltages higher than 0.8 V. Some of the boost converter circuits previously made by the master could operate at voltages close to 0.2 V.
The main idea was to make several JTs work in parallel. A printed circuit board with 6 JT support was created to implement the project.
Their output voltage must be fed to the input of a 5V buck converter, which could power or charge some external device. The circuit also has an Arduino used to measure the battery voltage and a display to display the value.
Step two: payment
First, the wizard developed a diagram of the device. You can download it below.
He ordered the board at the corresponding service for the manufacture of boards. Files for self-manufacturing or ordering a board can be downloaded here.
After making the board, I started assembling the components.
Step three: case
The master bought a plastic box for the case in the store.
In the case, you need to make several holes for the display of buttons, a USB connector.
Step four: display
The master glued the display with epoxy resin, then applied a protective layer of UV resin to the screen.
Step Five: Converter
The converter will supply power to the Arduino. The master soldered wires to the board and glued it inside the case.
Step six: Arduino
Since the Arduino has to measure the voltage of 6 batteries, the master uses 6 analog inputs: A0, A1, A2, A3, A6, A7, A8. Pins A4 and A5 are used to connect the display. The master soldered the ends of the flat cable to these pins. Additional cables have been soldered to the 5V and GND pins (common ground and ground/power for the OLED module). Cables were also soldered to pins D8, D9 for the button and its LED.
Step seven: connection and final assembly
All connections were made according to the scheme (not shown there only switch connections to D8, D9). The technician has installed the battery holders on the top of the case. I used glue-moment for fixing.
Two of them are connected in parallel – a coin-cell battery holder and one AAA battery holder. Thus, only one of them needs to be fitted with a battery when the device is operating.
Step Eight: Programming
After assembling the device, you need to load the code into Arduino. The code can be downloaded below.
JT_Bank.ino Step Nine: Device Operation
The video below shows the JTPB operation.
Note that the Arduino is powered by an external power supply. The reason is that the DC/DC converter cannot supply 5V output voltage when the system is connected to the load. Because of this, the Arduino ADC reference voltage and battery reading are inaccurate. Using a combined DC/DC converter can solve this problem.
In addition to the main task, the device can be used to check the battery charge level.
Despite some problems and shortcomings, the described device can be used to charge and power various electronic devices, saving costs and energy resources.