Wednesday, October 14, 2009

Scrounging Around…….

This post is similar to one I had made on BITS 360 a while back. Having finished my Bachelor’s degree from BITS-Goa, I’ve now transferred to the Pilani Campus. So this is my first post after coming to Pilani.

As was in Goa, here too several ‘poor’ students (a point to note is that the word ‘poor’ refers to the usual scarcity of money that college students, being college students, face, and not an actual financial constraint :-D) wanted to know where they could cheaply source components. Obviously, I feel it my moral obligation to provide scrounging references. Read on to find out where I usually source a large part of my components.

Some excellent sources for jugaad are mentioned below. The list format is -
"Old electronics - many students throw out...."
"You will be able to scavenge...."

  • UPS systems
    buzzers, relays, power transistors, resistors, SRCs, triacs, massive heatsinks, even more gargantuan transformers (these are bl**dy heavy), awesome lead acid batteries (be warned, a faulty lead acid battery may be the very reason for the UPS' demise :-/ )

  • Electronic ballast tubelights (the new kind of 'slim' tubelights), CFL bulbs (I find loads of faulty ones in BITS - just ask the electrician, he'll only be too glad to get rid of them!)
    Ferrite chokes, thick wire to make air core inductors, high voltage capacitors, diodes, SRCs.

  • Alarm clocks (I don't really know how these get damaged...most BITsians claim that they fell down, or someone sat on them - I personally think they were chucked at the wall when they woke their owner up too early in the morning! ;-) )
    High pitched buzzer / speaker, 32768KHz crystal, tiny gears

  • Keyboards, mice (optical and ball), CD/Floppy drives, other PC junk
    JACKPOT!!! - buttons, leds, capacitors, optical sensors (optical mice have a very cool 18*18 pixel CCD - Google ADNS2610; anyone looking for advice or interface details, buzz me, I've done this), motors, heck maybe even a working 12 / 5 / 3.3V SMPS!

  • Phones (the traditional telephones, and newer cellphones)
    Magnetics, audio stuff. Mobile phones are a veritable source of ultra-small components: you need a steady hand, an SMD rework station, and guts of vanadium-steel to take these babies apart. I've used LCDs, very powerful white LEDs, joysticks, memory card connectors, buttons, etc from (discarded) mobiles. Most Nokias use the BL5C / BL4C - this is an uber-cool LiIon (old) and LiPoly (new) flat battery, 3.7v @ 700-1200mAh. I've drawn 15Amps from this thing for 60sec! No kidding! My multimeter leads got hot and one of the tips actually melted. I would not recommend doing this at all - you may damage the battery irreparably, and worse still risk explosion-caused burns (remember the Nokia battery-replacement drive a couple of years back?). Still, the BL5C is very good for small bots and compact electronics. You can get it for 750 bucks (original) or 120 bucks (cheapo duplicate). The duplicate seems to work fine, but test it out before buying.

While the phrase “one man’s junk is another man’s treasure” fits aptly, be warned that scavenging can be time consuming and the components obtained from the abovementioned sources can be unreliable. Having issued my warning - good luck, and happy scrounging!

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