The tools is up to you to define based on your skills, You can assemble the circuit using only a solder iron and solder core if you have some assembly skills but here I share the tools that I used easily complete the assembly of the Surface Mounted Parts, you may find that some tools are extra but you consider that it depends on your capabilities.
- I used a low temperature profile solder paste from CHIPQUIK SMDLTLFP10T5
- I used precision tweezers to deal with the small components.
- The small size hot plate MHM30 from miniware is suitable for the size of my circuit and I used (optional) a digital microscope camera to inspect the assembly results.
The Circuit Schematic
The main component of our Circuit design is the TP4056 Lithium Battery charging IC, this chip could provide charging for one Lithium Cell at a time it means we can’t use multiple Lithium Cells to charge them together through one TP4056 Chip, and it could work through USB port and this is what we will include in our design.
It also has a temperature sensing input to measure the Battery temperature to regulate the charging current, and a programmable battery charge current depends on the used lithium cell reference.
The chip includes two charge status output indicators, designed as open drain outputs, check more details about this chip through its datasheet here.
Our schematic also includes a Battery protection circuit, I mainly used the DW01A Battery protection IC designed to protect Lithium batteries and increase them lifetime through its charger detect input pin and the MOSFET gate connection pin for charging cycle control then this chip has to be installed alongside with a MOSFET and this is what we will need in our schematic.
As Always I moved to Altium designer to draw the schematic related to my circuit design, and Here I placed the USB C connector as main power entry and I brought the TP4056 and DW01A chip and I connected it to a MOSFET, here I placed a Battery Header connector for charging OUTPUT, I mentioned that the TP4056 Has a programmable current charging pin that could be configured depending on the used lithium cell, I used a 1KOhm resistor to match the current needed for my small lithium Battery, you can check the chip datasheet to define the appropriate resistor value based on the Lithium Cell that you are using.
The Circuit Design
After getting the schematic ready I transformed it into a PCB design and placed the parts in a small board size layout as always, since this is a circuit prototype to test the parts connection then no many things to consider about the routing.
After getting the GERBER Files of my circuit design ready, I moved to JLCPCB and I uploaded my design files to place a PCB order from them, I selected the minimum settings for economic order price and due to the very small PCB design size I got my boards for free.
Charger Ciruuit Assembly
I put the solder paste on the components exposed pads, and placed the components to their placements on the board, I used precision tweezers for this task because I’m dealing with very small components here.
The next step is soldering, I’m very happy to use the cool small size soldering hot plate from miniware, especially because it matches the small size of my PCB designs.
I shared a microscopic view of the soldering process.
Do not forget to clean the board with some flux removal solvent,
I then added the Battery header connector and soldered the through hole pins of USB connector.
Test the Circuit
Here is my charging circuit ready to start, I placed the Battery to the charger and plugged the USB connector to a 5V power source and here we go, the red light indicates that the Battery is in charging mode, after waiting for some minutes the Red Light is turned Off and the green light indicates that the battery is fully charged then the charger circuit interrupts the charging current output to protect the Battery and here is my battery charged.
As I mentioned in the beginning of this article, this...Read more »