Tech Tear Down – Computer Mouse


1_computer mouse artsy PCB shot

I had the sudden urge the other day to tear apart another electronic device, the victim being the computer mouse that I use for my Raspberry Pi that happened to being lying so very innocently on my desk. The picture above is an ‘artsy’ flash shot of the inside of the mouse.

Taking it apart was easy. There was only one screw in the center of the undersided that I removed with my trusty old mini Phillips screwdriver. The bottom and the top plastic pieces easily came apart, revealing a PCB pressed into the bottom, connected to the wire coming out of the mouse. The PCB itself wasn’t attached with glue or screws, so it popped out easily.

2_computer mouse parts labeledYou can see the little red left and right click buttons in the image below. When you click the mouse, the plastic of the shell of the mouse hits the read button. It’s not plastic that makes the clicking noise when it hits the button, its the button itself that makes the noise. The scroll wheel has a third little red button under it that allows for the scroll wheel to click. In the middle, there’s a motion sensor that detects where the mouse is moving. Inside the black box on the right is a red LED, the ‘laser’ that lights up the bottom when the mouse is on. In addition there’s a multitude of caps and resistors.


In the images below, you can see the bottom of the PCB, and how it fits into the plastic casing. There’s a little transparent piece of plastic that goes under the PCB, and it helps focus the LED light. 3_computer mouse plastic casing4_computer mouse PCB in position



Tech Tear Down – Laptop Computer Charger

WARNING: DO NOT ATTEMPT TO DISASSEMBLE OR TAMPER WITH YOUR LAPTOP COMPUTER CHARGER; they contain giant capacitors which are capable of delivering fatal electric shocks if tampered with or touched. The charger used for this Tech Tear Down had not been plugged into a wall for over a year, and the capacitors were completely discharged.

Ever wonder what’s inside that little black box on your computer charger? Recieving yet more throw away electronics, I took apart an old computer charger to see what was inside.

Before I delve into what was inside, here’s a little background on what the little black box does. When you plug something into a wall, you’re plugging into your house voltage, which is usually around 120 volts, with alternating current (AC). That many volts is enough to fry most electronics, so there has to be a way to reduce the voltage and the current down to something more usable. That’s the job of the little black box on your laptop charger. It takes the 120 volts and steps it down to a much lower voltage, usually between 10-20 volts. You may notice a your charger getting hot if you have it plugged in for a while; that’s the extra voltage getting dissapated as heat.

It took quite a while to get it open, as it should, to keep the components inside from getting damaged or more importantly, touched. This first image is what it looked like with the black casing off. The printed circuit board and all of its components are encased in a few layers in metal and plastic to help dissapate the heat.

1_computer charger one piece metal shell

With the casing off, most of the guts were exposed. There’s great gobs of white glue, and a significant amount yellow plastic tape. In the middle you can see a capacitor (it has a smaller piece of yellow tape on it), or a component that holds and stores and electric charge. This would be just one of the caps (short for capacitor) responsible for zapping you should you open the charger up without discharging the unit first.

2_the guts with glue and tape laptop charger

Next I painstakingly removed all the tape and began to tear it apart to see all the components. It’s mainly made up of large capacitors and inductors (components that hold a current).

3_computer charger, labeled parts

I completely destroyed it, saving the ‘cool’ components. I got a nice 300Ω resistor (I didn’t have any of them), a giant 420 V 120 uF cap (good as a souvenir), some useless caps, and a decent small inductor I’ll try out on something. If you look at the tan PC board below, you can see that it’s well labeled as to where the components go, and every part has a name, like C1 or CX1.

4_computer charge, all the pieces together

Overall, it was interesting to take apart a computer charger. I saw some capacitor varieties I’ve never seen before.

The Flickering Candle LED!

Remember that Pi Candle I made a month ago?

I was doing a quick scan of the Makezine website, and I discovered an LED assortment with built in chips that make them flicker when DC power is applied! If I made my candle with one of these special candle flickering LEDs, then I wouldn’t need to connect it to the Raspberry Pi or Arduino. I could just power it off of a battery!

See the picture below, courtesy of Makershed:

candle flick LED courtesy makershed

Happy Arduino Day!

arduino_Uno R3

Today is the Arduino’s birthday!

For those who are laymen, the Arduino is a microcontroller, or a device that allows you to program circuits to do what you want. The Arduino  (there are many different models, but the most commonly used is the Arduino Uno) is open-source hardware, meaning anyone can build off of it and make changes to it, and it’s not for profit. The Arduino is used by makers to prototype electronics. The Arduino is an amazing tool for anyone interested in building something totally new.

To celebrate Arduino Day 2015, I’ve been working on my first 4X4 LED matrix using a shift register integrated circuit on a breadboard! I’ve built most of the circuit, but I have to fix some of the wiring so it’s not as crowded. You’ll notice that I tried to color coordinate the wires. I’m still working on the programming, but when I’m finished, the LEDs matrix will display some cool patterns!

4x4 led matrix prototype

Tech Tear Down – Toy Cellphone

toy story phone diagramReceiving the throw-aways  from my sister’s toy phone collection for use in my electrical endeavors, I opened up an old Disney store Toy Story fake cell phone to see what I would find. Basically it has  17 buttons, which create assorted noises and blink LEDs on the ‘screen’ and in the antenna. Or at least it used to, because the batteries are long dead.

Taking apart the back first near the batteries, revealed the capacitive printed circuit board for the rubber buttons. On the back side of it, there’s a couple 5% tolerance resistors. Under that, there’s an 8Ω speaker commonly found in many electronics, and you can also see the coin cell holders and the LED connections. The date on the PCB said it was made in June 2003. Other than the screws holding the toy phone together from the outside, the plastic snaps together and keeps the LEDs and PCB in place.

Being a throw-away item, I was able to obtain a few parts for my own use. The resistors are unusable, because the leads are to short, and I have not yet obtained a soldering iron. I always keep all screws from electronics, because I know they’ll come in handy someday.

100_3833parts salvaged from toy story cell phonetoy cell phone capacitive PCB

555 Timer – Make a Siren LED Blinker

image of 555 circuit on breadboard

Basically, you can use a 555 IC to generate a square pulse. Depending on how you wire it takes a DC input, like a 9v battery, outputs a blinking signal. Hooking an LED up to the output will cause it to blink on and off at a frequency dependent of the value of the size of resistors you use. There’s a couple of ways you can wire it up to do different things, but in this case, we’re going to operate the 555 timer in astable mode, meaning it takes a constant input, and outputs a pulse. From there, will take that pulse output and use a capacitor and resistor  to make a simple differentiator, which transforms the square wave into a much cooler spikey wave.

Here’s what you’ll need:

  • 555 Timer
  • 1 100uF Capacitor
  • 1 0.47uF Capacitor
  • 2 1MΩ Resistors
  • 1 330Ω Resistor
  • 1 680Ω Resistor
  • Breadboard
  • Various wires
  • 9v Battery or 4 AA 6v Battery Pack

Dont’ worry if you don’t have the exact resistors above. Swapping out different resistor and capacitors is half the fun of 555 timers. Provided you do it right, you’ll see differences in frequency and in the way the LEDs blink.

Wiring up a 555 can be a little messy sometimes. If you’re used to programmable circuit layouts, the 555 wiring is much messier than that. You’ll have to watch where you plug things in.

Basically the 555 operates in its astable mode, and generates a square wave. Then the differential section creates a spikey wave which you wire to the LEDs. Here’s what the progression of the signal from beginning to end.

graphs of voltage to time

Build your circuit based on the schematic below, referring to my image for the  wiring setup. Watch the polarity of the LEDs and caps though. The interesting thing about this circuit is that one of the LEDs is wired in reverse, meaning the red LED in the image below is wired backward compared to the green one. On the above graph, you can see the differentiator output voltage alternates between negative and positive. It’s like the voltage goes backward then forward. When you have two LEDs hooked to the circuit opposite each other polarity-wise, then they’ll blink back and forth. If you put them both in the same polarity-wise, then they’ll blink at the same time, either both on the negative spike, or both on the positive spike.

If you’re finding it’s not blinking or working consistently, the problem most likely lays with the values of you caps and resistors. The two resistors in the astable mode 555 control its output frequency. The higher the resistor value, the slower the frequency. It’s best to stay with high value resistors when dealing with LEDs so the blinking will be visible to your eyes. For the differentiator, stay with lower resistor values so the LEDs don’t get too dim. Keep the differentiator cap higher in uF than the 555 cap. There are mathematical equations that relate resistor and capacitor values to frequency and the differentiation factor, but that’s a little to complicated for here.

fritzing 555 diagram

Tech Tear Down – Rechargeable Crank Flashlight

A crank flashlight is wonderful to have on hand; you never have to worry about the batteries. I have one that I use all the time. I decided to take it apart to see exactly hodiagram of flashlightw is functions, and there’s really quite a few things in there. The flashlight has one big button plus a crank you turn to charge it up. If you click the button once, all three LEDs light up, if you click it again just the center one lights up, and clicking it a third time shuts it off.

I started by remove four screws on the back to reveal the inside.

Inside, there’s a DC motor that connects to the crank shaft. When the crank is turned, the DC motor turns too, which generates a voltage, and the battery charges up. The push button, which is right in the middle of the PCB (printed circuit board), whidiagram of PCBch is the only input to the system. All of the capacitors, resistors, and diodes are used to control the process through which the LEDs cycle through the on and off cycle. I was interested in the four-legged integrated circuit (IC) in the middle. I’m used to seeing eight-legged ICs.

Next I removed the screws (circled in yellow in the above pic) holding the PCB to the black box. From there I could remove the clear plasticflashlight shell shell around the light, and pull the PCB away to reveal more screws that attached the whole chunk to the outside shell. There’s only three little LEDs that provide all the light given off by the flashlight!

Finally, I took apart the black box which contain the gear mechanism for the crank. The three gears are set up so that turning the top gear (connected to the crank shaft) slightly makegear mecs the bottom gear (connected to the motor) turn a lot. You can see there’s some slimely stuff that looks like petroleum jelly all over the gears to help the turn smoothly and quietly.

After I took it all apart, I put it back together using only my trusty little phillips screwdriver.