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built of paper.

Monday, March 12, 2018

USB Ni-MH Battery Charger Part 3-The Schematic and Layout

I started this project thinking that I would try to fabricate it as I have never tried to fab a board before. But after I soldered on a perf board, laziness kicked in and I think I would just leave the project as it is.

Ni-MH Battery Charger Prototype

Ni-MH Battery Charger Prototype Topview

I goofed up big time during my component purchase. I wanted to order BQ2002PN, but because RS Online only sells them in a pack of 5, and I only wanted 3, I opted for another part, with “similar name. I thought it was the same! I bought 3 BQ2002TPN! I didn’t notice that until my controller just wouldn’t switch my current source on. I thought my soldering really sucks so much to the point that such a simple controller circuit wouldn’t work.

I noticed that the current source worked when the controller is not there, so I started poking around the pins and matched the readings with the datasheet. I found some discrepancies. My LED lighted up even though the current source was switched off. I’ve forgotten how did I find out I bought the wrong part, but that’s definitely a facepalm moment.

Anyway, I realised afterwards that BQ2002TPN only comes with temperature increate rate termination, dT/dt. Another facepalm moment, as my resistors were all designed for a dV/dt termination….. Another round of rework and adding in the thermistor, the design finally worked!!! And it worked so well that I could not believe it. It really terminated the charging after it detected a dT/dt of the battery. I have a plan to record and show the voltage waveform, but that can only be done during the weekend…

And for the schematic:

USB Ni-MH Battery Charger schematic

Still need some clean up. I’ve even picked-up FreeCAD to create 3D Model and produced a layout for this board. Well, maybe this project is not going to be fabricated, but the experience will definitely come in handy next time. Smile

image

The next post would be the end of this project series, it’ll be just a short post to describe how did I choose the resistor value to parallel with the thermistor. Hope you guys have fun reading this. Until next time!


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Sunday, March 11, 2018

USB Ni-MH Battery Charger Part 2-The Current Source

So I’ve looked around on the Web for a suitable design for my controllable high-side current source. I would like it to be as simple and cheap as possible. The first one is the usual Op Amp and FET combination current source circuit. But to power up an op amp using USB 5V I would need a rail-to-rail type, which is not that cheap. I stumbled upon this design. The answer also improved the initial design by adding a diode.

Constant Current Source

The idea is that, the voltage drop across R10 will be one diode drop, ~0.7V, so the current will be determined by the resistance of R10. Q1 is the ‘switch’ to control the current source from BQ2002. Q2 will adjust Vce accordingly to pass the current determined by R10. This also means that Q2 will have a big voltage across CE junction. 5V minus ~1.6V from battery, and 0.7V across R10, there’s still 2.7V across Q2, and we are passing around 0.7A. So that’s ~2W of power loss on Q2. This is not an efficient design, but it’s the simplest and easiest to be prototyped with my current stocks.

I needed to try this before buying any Power PNP. I used a configuration known as Quasi Complementary Pair to try my circuit. With a jellybean PNP and a Power NPN, they act as a Power PNP transistor. The circuit was commonly used during the old times when Power PNP had lower quality due to process technology. Anyway, my circuit worked, and I proceeded to buying a couple of TIP32 (as they are the most common parts and the cheapest….) and some BQ2002.


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Monday, March 05, 2018

USB Ni-MH Battery Charger Part 1-The End and The Beginning

These series of updates will focus on building a Ni-MH battery charger powered from USB. The main motivation is this: my battery charger from Panasonic got destroyed.Panasonic BQ-CC16

It is a Panasonic BQ-CC16. I bought it in 2014-15 time with 4 of the Eneloop cells. My wireless mouse is using one of the cell and they last so long with one charge, so I only recharge them when about 2 of them are discharged. Anyway, my mouse was out of battery that day, so I replaced it with another cell, but all of them apparently were already discharged. So I brought out the charger, pop it the cells and switched on the power. I saw sparks and fire coming out form the charger and soon, my other devices connected to the same extension were out of power. I had just burnt my fuse in the extension. Luckily, the extension still works after I replaced the fuse, and it is cheap. But the charger is not….

Arcing mark inside the cahrger

See the scary burnt marks from the arcing inside the charger? I’ll think twice now for placing my handphone charger so near to me when I am sleeping…

IMG_20180124_221731

It seems like the arcing happens at the trace near R02 and TP10. Very strange as they are not that close, and nobody has any complaints about this charger being that dangerous. So, maybe I misused the charger? I only charge like 3-4 times a year, so maybe some dusts have accumulated inside and caused the arcing? I would appreciate your comments if you guys have any idea how this happened…

PCB

The top side of the PCB. Seems well build to me. No flimsy dangling wires around. So why did it arc??? And the arc even blew my fuse…

Since I don’t know how the charger work, I can’t fix it. Maybe I’ll just connect some sort of DC supply to the secondary side.

Anyway, I initially wanted to buy a new charger, maybe multipurpose one, for Ni-MH and also Li-ion. But I thought that this would be a good project to build my own charger from scratch. I’ve been trying to build one, but the lack of motivation pushed me further and further, until this day…

I’ve looked up on several off the shelf ICs, the MAX712 and LTC4060. They seem easy to use and are quite promising. But their prices are to high for a possibly one off project like this. (Or would anyone wants to buy ? Hahaha) So I searched deeper and found BQ2002. It’s just a controller to switch a current source on and off based on the battery condition. So, I locked it down to this controller IC and started to research how to implement the current source. Stay tuned to Part 2, for my journey into the battery charger realm!


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Sunday, October 30, 2016

Arduino Uninterruptible Power Supply (UPS) Improved

A reader left a comment on my UPS post, he asked me to share the ‘improved’ design.

I would not really categorise it as an ‘improved’ design because I simply removed the P-MOSFET.

I also added a switch when they would not want the Arduino to be powered on.

Schematic

Arduino UPS

The UPS was meant to power up an Arduino Nano, from USB or a Li-Ion Battery.

I hope this blogpost will be helpful for anyone doing a small UPS for Arduino. Cheers


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Friday, April 29, 2016

Magnetic Levitation with Arduino

Hello guys! I posted my Magnetic Levitation project on Hackster.io! It is really a great site to share your own project!
Here is the link to my project: https://www.hackster.io/chanhj/magnetic-levitation-8c3ad0?ref=custom&ref_id=45065&offset=4

Magnetic Levitation

Even though I’ve posted some brief intro and instructions there, they are not very detailed. But then I am a lazy guy, so if you need more details, just leave a comment, maybe I can improve the post?
It's made with a U3503 Linear Hall Effect Sensor, a MOSFET and a LED. :D It is that simple.

Magnetic Levitation Circuitry

Magnetic Levitation Circuitry Interfaced with Arduino UNO


My code is copied directly from another guy listed in my hackster project. All credits go to him, I only edited the PID parameters. However, his code does not compensate for the field generated by the coil itself, maybe I can research more on that, keep planning... Less doing, all the time...


I have since then found another levitation project to make, it’s a rotating globe, with blinking LEDs! Who doesn’t love LEDs right? Until next time, keep making things! :D


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Tuesday, March 29, 2016

Experiment 8-AC Single Phase Induction Motors

I started to take photos of my Power Laboratory experiment for no reasons since my first lab work. Since many do not have the chance to actually operate an AC machine( even my electronics engineering course mates hahaha), ceiling fan and machine machine excluded, I think it’s a good idea I share the photos out.
My theory might not be perfect, so please correct me if you spot any mistake of any kind, I thank you in advance. ( But I wouldn’t go into too much theory though…)
My experiment is divided into Split-Phase motor, Capacitor-Start motor and Capacitor-Run motor. These are all induction motor, operating with a single phase supply. Thus we need to create another phase of supply to provide a rotating magnetic field to turn the rotor.
Capacitor-start motor
We used the capacitor-start motor without the capacitor, functioning as a split-phase motor. The auxiliary or the start winding has a high resistance and inductive reactance, while the main winding or the run winding has low resistance and high inductive reactance. Because of the different ratio of winding resistance to the inductive reactance, the run winding current  lags the start winding current, creating a phase difference between them. This creates fields that are out of phase, which in turn produces a rotating magnetic field in the stator. This develops torque in the rotor, starting the motor. ( And almost all of these are copied from my lab manual. Credits to whoever produced these sheets. )

The starting current of split-phase induction motor is 4 to 5 times of their full-load current, thus the starting period has to be short to prevent over heating. ( And I felt the heat after applying power for just 3 seconds!) A centrifugal switch will switch out the start winding ( which has high resistance and will overheat and burn out easily ) once the rotor reaches certain rpm.
Capacitor of capacitor-start motor
A big ass capacitor of the capacitor start motor.
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The construction of the motor
DSC_3056
Showing the auxiliary winding ( the thinner wire) and the main winding ( the thicker wire).
DSC_3057
Closer shot of the windings and also observe the clearance of the stator and the rotor.

The operation of a capacitor-start motor is pretty similar to a split-phase motor. Now we connect the capacitor in series with the auxiliary winding. This provides a rotating magnetic field as well. The cap and winding are disconnected with a centrifugal switch as well.
DSC_3059
This is the full setup, including ammeter, voltmeter, wattmeter and electrodynamometer.
DSC_3060
Another type of capacitor, mounted for capacitor-run motor.

The capacitor in capacitor-run motor is always connected to the auxiliary winding and power. It doesn’t get disconnected with centrifugal switch. The manual states that it’ll be more quiet at full load, but honestly I didn’t feel the difference. Still vibrating like no body’s business!


Determining the starting torque
Posted by Chan Hao Jie on Monday, March 28, 2016

This video was taken to find out the starting torque. The scale was too fast for my slow eyes! :(

Measuring the starting current.

Posted by Chan Hao Jie on Monday, March 28, 2016

Another one for measuring starting current.
DSC_3061
DSC_3062
I would slowly update this blog with my previous and next experiment. Other than Power Lab, I have Advanced Power Electronics Lab as well, dealing with thyristors! Stay tuned. :D
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Saturday, March 12, 2016

Feedly- My Daily Newsletter


Logo from Feedly website

I have been using this for over one whole year now. I think this is a very useful tool so I want to share this out.
feedly GUI
Feedly main screen, captured from the website introduction page

Feedly is a subscription tool. It is like a newspaper service, but it operates online. You choose whichever journals, articles or even YouTube channel you like, Feedly will collect their updates and arrange them nicely in your Feedly homepage.

Using Feedly is simple, just go over to the website, register and login, subscribe to your favourite sites so you would not miss any of the updates. So you can subscribe to my blog too if you want!

The biggest challenge for me before using Feedly is that I have too many websites to keep track of. And you would not have all the time to keep refreshing the website to check the updates. And e-mails are quite annoying for me. I used Google Reader before it is gone, then I found Feedly. My subscription ranges from Electronics and Arduino stuffs, to homebrew comical videos and Japanese lesson.

So, use it now to help in your reading. I call mine a One-Stop Reading Corner in this distracting world of Internet.

P/S I am not in anyway affiliated with Feedly. But it would be nice to give me like a one month premium service maybe? Haha.
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Sunday, February 07, 2016

Happy Chinese New Year

It’s almost New Year here in Malaysia. My Strike Freedom is still in building process. So I did some photo shooting with a “ang bao” (red packet).
Strike Freedom with ang bao
Strike Freedom is still my favourite Gundam until today. Maybe it’s because it is the first model I ever watched? Nothing beats childhood memories I suppose.
DSC06200
This is my sister’s calligraphy writing for Chinese New Year. She got the first prize for a contest in her school with this writing. Sure, it needs some polishing, but at least it’s better than mine.

So, happy Chinese New Year everyone! Wish you guys have a wonderful and prosperous year ahead!
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Tuesday, February 02, 2016

MBF-P02 Gundam Astray Red Frame from Daban Model

Hi guys. This is a Gunpla I finished like months ago. I did not have the time to properly take photos for this awesome figure! ( Its build is actually more playable than Akatsuki… My Akatsuki has a very weak leg peg that keeps falling off…)
Anyway, this is my first time taking photos for gunpla ( okay, not the first time, but this is the first trial of me trying really hard to pose the figure!), used one whole day with some intermittent breaks haha.
MBF-P02 Gundam Astray Red Frame -002
The standing pose. I tried hard to make it as cool as possible…
MBF-P02 Gundam Astray Red Frame -003
Side view
MBF-P02 Gundam Astray Red Frame -004MBF-P02 Gundam Astray Red Frame -007
I was trying a sword drawing pose. It turned out harder than I thought. Now I can appreciate the flexibility of human joints.
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First try of a dynamic pose for a Gunpla. But it’s a must for Red Frame. It’s built for this!
MBF-P02 Gundam Astray Red Frame -017MBF-P02 Gundam Astray Red Frame -018MBF-P02 Gundam Astray Red Frame -019MBF-P02 Gundam Astray Red Frame -020
This would have looked nice if I am taking photos outdoor. The reflection would be amazing.
MBF-P02 Gundam Astray Red Frame -022MBF-P02 Gundam Astray Red Frame -023MBF-P02 Gundam Astray Red Frame -025MBF-P02 Gundam Astray Red Frame -026MBF-P02 Gundam Astray Red Frame -028MBF-P02 Gundam Astray Red Frame -029MBF-P02 Gundam Astray Red Frame -032MBF-P02 Gundam Astray Red Frame -033MBF-P02 Gundam Astray Red Frame -034
Here comes the big sword!
MBF-P02 Gundam Astray Red Frame -035MBF-P02 Gundam Astray Red Frame -036MBF-P02 Gundam Astray Red Frame -037
But apart from looking cool behind, sword form… is really just a prop… LOL.
MBF-P02 Gundam Astray Red Frame -039MBF-P02 Gundam Astray Red Frame -041
Now I can fly!
MBF-P02 Gundam Astray Red Frame -043MBF-P02 Gundam Astray Red Frame -044MBF-P02 Gundam Astray Red Frame -045MBF-P02 Gundam Astray Red Frame -046MBF-P02 Gundam Astray Red Frame -047MBF-P02 Gundam Astray Red Frame -048MBF-P02 Gundam Astray Red Frame -049MBF-P02 Gundam Astray Red Frame -050MBF-P02 Gundam Astray Red Frame -051MBF-P02 Gundam Astray Red Frame -053MBF-P02 Gundam Astray Red Frame -054MBF-P02 Gundam Astray Red Frame -055MBF-P02 Gundam Astray Red Frame -056MBF-P02 Gundam Astray Red Frame -057
This is how I am posing Red Frame on my shelf now. By the way, I bought a new shelf, that’s why I pulled this model out of its box. It’s a shame not to showcase this guy. It’s stunning!
That’s all from me. Feel free to comment on my lousy skills, be it building or photoshooting. I made a lot of mistakes everywhere. Cheers!
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