Sunday, February 26, 2006

Handshake for Power and all that...

10:56 am on 27th February 2006, I get a mail from Professor Prabhat Ranjan (from DA-IICT), my collaborator in WSN (for more about WSN, see my previous post) saying that he has bought a handshake powered torch and he intends to explore the feasibility of using the built-in dynamo for powering WSN nodes. Good Idea I say. So we decide to first try these generators on a suitable Homo Sapien. Someone who is a keen and regular jogger or likes to bike. We could hang the generator around his/her neck and see how much power it belts out.

I suggest him a way to measure this power. Use one of the plenty of AVR Butterfly devices I have in stock, courtesy Lars Aarrestaad from Atmel, Norway. Now the Butterfly is a really cool portable computer as you see here. In its less than credit card sized footprint, it packs a LCD display, AVR controller, piezo buzzer, thermister based thermometer, LDR based light sensor, a voltmeter, 4-way joystick and a 4-megabit dataflash data storage chip. All this is powered with an on board 3V lithium coin cell; and it costs USD20 approximately. Nice price, nice power consumtion..

My students Gaurav Ajwani (ICE, 8th semester) and Sparsh Arun (ECE, 8th semester) have been working on a bicycle computer using a Butterfly and they are almost done (you would get to read all about it in a future issue of MakeZine ), so they had all the software tools to adapt their bicycle computer to record power being outut from this handshaking generator. Just record the output voltage on a fixed resistor, R, and power is V*V/R. Sample close enough and keep adding area under the curve and you would get an estimate of energy being produced by the generator.

Professor Ranjan... you would have this recording contraption by the end of the week in your mailbox :)

Dhananjay Gadre


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