CNC Plotter

Using machines to do human tasks has been a focal point of human development for the past decade. A CNC Plotter is a minor step in that direction by using machines to draw on paper.

Engineer

Alec S.

Area of Interest

Engineering, Finance

School

Homestead High

Grade

Incoming Sophomore

Final Milestone

My final milestone is…

Third Milestone

My third milestone is…

Second Milestone

My second milestone is…

First Milestone

My first milestone is…

Starter Project

For my starter project, I chose to do the MintyBoost battery charger. It supplies power from two 1.5V double A batteries contained in a battery holder to the USB port on the circuit board and the connected device. The majority of the components on the circuit board, like the boost converter chip, IC socket, ceramic capacitors, electrolytic capacitors, power inductor, and 3.3K resistor are used to transfer power from the batteries to the connected device. The rest of the components, which include the 75K 1% and 49.9K 1% resistors and diode, are used for less important tasks, like figuring out what type of charger is connected. 

Parts List

R5 Resistor: The stripes are in orange-orange-red color order, which indicates a 3.3K resistor. This resistor is used to improve the high current capability of the boost converter chip. Something to note about this resistor, and all resistors in general, is that they are non-polar, which means they can be inserted any way into the circuit board. You don’t have to worry about putting it in “backwards”.

R2 and R4 Resistors: These resistors have the pattern Violet Green Black Red Brown, which means that they are 75K 1% resistors. These resistors are used to figure out what kind of charger is connected.

R1 and R3 Resistors: These resistors have a Yellow White White Red Brown pattern, which indicates that they are 49.9K 1% resistors. These resistors serve the same purpose as the R2 and R4 Resistors, which is figuring out what kind of charger is connected. The only difference between these two are their size and their color pattern.

C1 and C2 Capacitors: These ceramic capacitors are also non-polar, so they can be placed into the circuit board in any orientation. The capacitor in the C1 slot is responsible for stabilizing the output voltage, and filters out high frequency noise so that the 5V output is nice and smooth. The C2 capacitor is used to stabilize the internal reference of the boost converter chip. This keeps the chip stable so that it will generate a voltage as precise as possible.

D1 Diode: This diode is used to ensure that energy is transferred from the batteries to USB port, and not the other way around. Diodes have a special property that allows current to flow only one way, and because of this, the diode has to be inserted in a certain way into the circuit board, and is not non-polar.

IC Socket: This socket protects the boost converter chip and ensures that the boost converter chip can be replaced. It is placed over the resistor in the R5 slot.

L1 Power Inductor: This component is used by the DC/DC converter chip to store and convert power from low voltages to high voltages. Inductors are just a coil of wire, so they have no polarity, and can be placed either way.

C3 and C4 Electrolytic Capacitors: The two electrolytic capacitors placed in the C3 and C4 slots help smooth both the input and output voltages, to keep them stable during the up-conversion. They are used for low frequency noise, and are often paired with a ceramic capacitor. Electrolytic capacitors are polarized and must be placed correctly or the circuit will not work. The longer wire is the positive one and must be placed in the positive hole in the circuit board, and the shorter one is meant for the negative hole.

Boost converter chip: This chip is responsible for upping the voltage in the system while lowering current. It is inserted into the IC Socket, and is not soldered on to the circuit board, so that it can be replaced.

Battery holder: Contains two double a batteries and supplies their power through red and black cables that are soldered onto the circuit board.

USB port: A USB-A charging cable can be inserted into this port and power can be drawn to the connected cable/device from the system.

First, I soldered in the resistors. The R5 Resistor came first, then the R2 and R4 resistors, and then the R1 and R3 resistors. After that came the ceramic capacitors, which went in the C1 and C2 slots. Then came the D1 Diode, which was the first polar component I had to solder in, so it had to be inserted into the circuit board in a certain way. I then soldered in the IC socket, which went directly over the R5 resistor. It had eight connections and fit neatly into the circuit board. After that, I soldered in the power inductor in the L1 slot and electrolytic capacitors in the C3 and C4 slots. I then soldered in the wires of the battery holder and inserted the boost converter chip into the IC socket. I then checked that the circuit board/battery holder wasn’t warming up, and it wasn’t, so I moved on to check that the proper voltage was surging through the circuit board. Everything was in order, so I finally soldered in the USB port. I had accidentally left the batteries in while I soldered the USB port on, so they got really hot, which was bad. I replaced them with new batteries and plugged in a charging cable and my bluetooth earbuds case to test if it was working. The charging indicator light came on, so everything worked perfectly.

I did run into a few problems while working on this project. The 75K 1% resistors that went into the R2 and R4 spot on the circuit board would not go in all the way, due to their wire ends being too long. I attempted to bend the ends even more so that it would fit, but to no avail. I ended up just jamming them in there and praying that it would work. Luckily, it did. The resistors were elevated a bit off the circuit board, but that turned out to be helpful, as the 49.9K 1% resistors that went in the adjacent spots fit easier because there was more room closer to the circuit board. Another problem I encountered was when I soldered in the USB port. I accidentally left the batteries in while I was soldering, so the batteries and the circuit board got very hot. It’s a miracle that nothing exploded. I let the whole thing cool for a bit before swapping out the batteries for new ones and testing it.

Overall, this project was a good way to practice my newly acquired soldering skills for my main project, learning how to properly document my work, and acclimating to the BlueStamp environment. I definitely learned a lot that will be useful for my main project.

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