标签: interest

Hi, long time no see! This September will be a different one for me, since I am not a student anymore... I was busy for my Final Year Project (also known as Graduation Project, or 毕业设计) in the last term. And after finished all the schoolworks in May, I became lazy... I still remember how happy I was when I got to know logic gates in my first year in University. However, I have not tried all the logic gates that I have yet... Fig. My DIP IC collection in these 4 years Now I am working in a technology company as a junior engineer. My main duties include the development of some sensors.   Although the workload in school was heavy, I still do other hands-on works for interest. Here are just some of the tasks over the past few months..   Reuse and repair a LCD from an old notebook computer ------------------------------------------------------------------------------- A friend gave me a very old notebook computer. However it could not be turned on... Since it was too old, I decided not to repair it... Fig. A very old computer (manuf. in 2000), cannot boot up   To re-use the LCD panel, I bought a LCD kit from Taobao. The model number of the panel is LCM14C421F, from Toshiba. After connecting the panel to the kit, the screen was grey out.   Fig. Re-use the panel as a monitor with a TV kit, however, the screen is grey The vendor of the kit said it was due to the bad OP262. I could not find one on my hand, so I replaced it with a general Op Amp, LM358. Although from the datasheets of OP262 and LM358, LM358 has a much lower performance, it worked.   Fig. Replace the OP262 by a LM358   Fig. The LCD works fine afterwards I was surprised that it could show the contents clearly...   Fig. The LCD Kit   The Li-ion battery of the notebook was taken apart. Then with some 18650 battery cases, they were used for external chargers, which could be used for phones.   Fig. The 17670 Li-ion Battery   The remaining parts were put to recycle.   ------------------------------------------------------------------------------- Replace a circuit board of a LCD TV ------------------------------------------------------------------------------- The power circuit of a LCD TV went out of order. The 5VSB was only 0.x V. The markers (model number) of the SMPS controller could not be seen clearly. And I could not find the same board online for replacement. So it was replaced with a 'universal' LCD power board. Because the backlight circuit was not compatible with the old one, reusing the old circuit would be good. Fig. Taking apart of the backlight circuit   ------------------------------------------------------------------------------- Repair a router ------------------------------------------------------------------------------- I like collecting routers and re-distributing to friends. Sometimes I could buy a 2nd-hand router from local street vendors (地摊) for as low as HKD$5 to $10 each. Then I will check and give out to people who need a router. Some routers worked fine. While some needed firmware upgreades. And a few were bad. I would try my best to repair and usually my job was successful, but not always. Fig. Top I like collecting routers; Bottom: MP9141ES replaced by LM2596 ------------------------------------------------------------------------------- Repair an induction cooker (failed) ------------------------------------------------------------------------------- An induction cooker was out of order. The fuse was burnt. The IGBT and the AC-DC bridge was bad (conducting). After replacement, the fuse would not blow out. However, after started the cooker for a few seconds, it would stop heating. Fig. The induction cooker and the power board I tried replacing the transistors driving the IGBT and some other components, but still failed. ------------------------------------------------------------------------------- Repair a notebook ------------------------------------------------------------------------------- The IC in QFN (or DFN) packages were not well soldered (dry joint), making that the notebook out of function. After soldering the ICs, everything was fine then. Fig. Re-solder the USB3.0 and Ethernet IC in QFN packages   This problem is quite commonly seen in different devices. The side (not only the bottom) of the pins should be soldered properly in order that the joint would not be broken in high temperature. However, I heard that JEDEC standards do not require this (the side to be soldered)... ------------------------------------------------------------------------------- Repair another notebook ------------------------------------------------------------------------------- Just to improve the heat conduction. Fig. Improve the heat conduction by aluminium sheets ------------------------------------------------------------------------------- Repair another notebook ------------------------------------------------------------------------------- Broken joint for the graphic chip (in BGA package). Hopefully it could run for a long time. Fig. Heat re-flow on the graphic IC ------------------------------------------------------------------------------- Repair another notebook ------------------------------------------------------------------------------- The SMPS controller was out of order, causing the notebook could not be started. Fig. Replacing the notebook's controller IC, MAX1999 ------------------------------------------------------------------------------- Repair a radio alarm clock ------------------------------------------------------------------------------- Bought a radio alarm clock for $20 from street vendors 地摊. The power circuit was burnt and repaired. I changed it to a regulator circuit by MC34063 with input voltage 12V, output 4.5V. Fig. The alarm clock ------------------------------------------------------------------------------- Repair MP3 players ------------------------------------------------------------------------------- I bought 5 MP3 players for HKD$10 each. I saw that actually the scratch-protective sheets were not torn - the MP3 players could be brand-new! However, none of them could be charged no matter how long they were connected to external power. The battery could be over-discharged. Fig, The MP3 players, and installed dedicated charger IC (left-bottom)   I found that there was no Li-ion charge IC inside. The Li-ion battery is connected to the USB port power via a diode and a resistor only. Then the charging current is limited by the PPTC of the battery... Although they were using Samsung's flash, the charging circuit was poor... Then the battery was taken apart and charged separately. After that, each of them has been installed with a TP4056 IC for charging. ------------------------------------------------------------------------------- Repair an air dryer ------------------------------------------------------------------------------- Replaced the rusted push button of an air dryer. Fig. The control board of the air dryer   Replacing a small component could save money and the appliance. -------------------------------------------------------------------------------   My on-going projects: 1. A school website (not paid) 2. A PCB for a robot 3. Have fun on Raspberry Pi and Banana Pi Fig. A Raspberry Pi and Banana Pi, from Taobao 4. Play with Intel Galileo Board Fig. The Galileo Board, also from Taobao 5. DIY a simple air cleaner 6. DIY a ice box (by Peltier effect panels)   As time went by, I will leave (actually already have left) the University. I will miss the lovely cats. Fig. The lovely cats in the University