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Showing posts from August, 2010

Reed Switches

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






Printed Circuit Boards - Construction Materials

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 them with heat a…

The Insides!

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 …

Restoring P89V51RD2 's Bootloader

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'sUNIPro 110uis one such programmer. The photos below explains the process of restoring t…