Electronics FAQ

Read an FAQ on "reed switches" here and the wikipedia entry here . Here is what a pack of 1000 pieces of reed switches looks like.

There is a lot of confusion amongst students and fresh graduates with regards to the PCB fabrication process. I have accumulated some knowledge from around the web (References: Link1 | Link2 ) and added some of my own here to serve as a ready reckoner of a few important notes regarding PCBs. PCB Process in Brief: Copper laminate -> Drill board -> Deposit Copper -> Photolithography -> Tin lead plate or finishing -> Etching -> Hot air level -> Solder mask -> Electrical Testing -> Routing and V-scoring -> Product inspection -> Final cleanning -> Packaging. PCB Terminology Base Laminate - That sheet of insulating material (a.k.a. dielectric ) to which a thin copper foil is affixed on either or both sides. This material is constructed by repeatedly uniting two or more layers of material together. The process of creating a laminate is lamination , which in common parlance refers to the placing of something between layers of plastic and glueing...

What better way to teach students about architecture of embedded systems than to actually open up a few and show it to them? We opened up a digital camera, an iPod, a GSM Cell phone, a TV game and a few computer accessories. We then stuck their innards between two thick pieces of A4 sized transparent plexiglass each and bolted them together to form exhibits. For the digital camera, we even printed out a pair of transparencies to outline the various sections on the main board. During the workshops, they proved to be a great practical teaching aid for exposing students to some real life design. After a few workshops, the glue gave way and the various sections inside the exhibits started falling apart. Since the sides were open, the dust made matters worse. And because we used to pack all of these 5 exhibits together, the bolts on each of them ended up scratching the surfaces of the plexiglass. In the second version of these exhibits, we ought to make the transparent box sturdier and dust...

If you have used P89V51RD2 a lot, you would have realised that many times it happens that the microcontroller refuses to be recognized by FlashMagic and then you have to resort to replacing the microcontroller with a new one. Assuming that your hardware circuitry and computer are free from any problems, there are only two things that could have gone wrong - your microcontroller has suffered an internal hadware failure (maybe because of overvoltage or ESD) or the bootloader residing inside the microcontroller has got corrupted. Microcontrollers with spoilt bootloaders can easily be fixed by re-programming the bootloader into their flash memories. So before dunking those seemingly dead micros into the waste baskets, try to resuscitate them by reprogramming their bootloaders. Heres how you can do this using a Universal Programmer: Step 1: Acquire a "Universal Programmer". UC Micro System's UNIPro 110u is one such programmer. The photos below explains the process of...

We have all used InfraRed based remotes to control various appliances around our house. All these remote work by transmitting data in form of flashes of infrared light - and wherever one needs to transmit data, there is always a protocol involved. The RC-5 protocol from Philips has been used in TVs, VCRs and other appliances since the past three decades. It was developed by Philips but was adopted by many other manufacturers. Now days RC-5 has been superseded by RC-6 and various other protocols from various other manufacturers. These newer protocols have better features and are more flexible. San Bergmans's KnowledgeBase on Consumer IR is a nice place to lookup information (protocol specs, circuits, embedded code) on any of the old or new IR based protocols. Here is how a RC-5 TV remote control transmitter unit looks like: And here is a InfraRed receiver/demodulator: A RC-5 codeword is 14 bit long. The first two are the start bits, then comes the toggle bit and finally the 5 bits ...

I²S stands for Inter Integrated Sound and is similar to the I²C which is used for transmitting data between Chips on a circuit board. ( wikipedia article on I²S). I²S is used for connecting digital audio devices together, (for example between the main processor and the audio codec chip on cell phones or computers or between the CD transport and the DAC in a CD player). I2S interface consists of at least 3 signals: Clock Left right clock Data line The eKA8562A Chip which is a USB Audio Controller (and can be used as an oscilloscope ) sports an I²S interface. Here are a few signals captured at the various pins (I²S output) on this chip: Pin 5 of eKA8562A - I²S BCLK Output Clock - This signal is used as the clock to latch in the bits appearing on the data line. Pin 6 of eKA8562A - I²S LRCLK Output Left Right Clock - This signal is used to tell the receiving devi...

Enterprising undergrad engineering students can achieve a lot if given the right set of tools. Once you level up to designing some complex circuits, a signal generator and an oscilloscope would definitely go a long way in helping you in debugging your projects. I bought my first oscilloscope ( Acute DS1202 200MHz PC based) for INR 37,500 after accumulating my salary for 4 months at my first job. But I always wished I has an access to an oscilloscope as a student. It seems that now days there is a low cost option for students to use: the PCs sound card. Most modern motherboards have an onboard Audio Codec Chip which is used to accept and output sound, you can find atleast 3 audio jacks labeled Microphone, Line In and Line Out on the back side of your CPU Cabinet. You can then use specialized freeware/shareware applications which can turn your PC into an Oscilloscope/Signal Generator. Here are screen shots of some of these: Oscilloscope 2.51 (aka Winscope) - the captured wavefor...