[Olpc-socal] [support-gang] What Sensors and Where To Buy?

[Kevin Mark]

--- On Thu, 9/20/12, Caryl Bigenho <cbigenho at hotmail.com> wrote:

From: Caryl Bigenho <cbigenho at hotmail.com>
Subject: [support-gang] What Sensors and Where To Buy?
To: "support-gang at laptop.org" <support-gang at laptop.org>, "IAEP SugarLabs" <iaep at lists.sugarlabs.org>, "OLPC SoCal" <olpc-socal at laptop.org>
Date: Thursday, September 20, 2012, 8:37 PM








Hi…


OK, here I am again with another "dumb" question… well, maybe not so dumb after all as I'll bet there are others out there who could also use this information. On the OLPC wiki there are several very nicely illustrated instructions about how to make sensors to use with the XO… temperature, humidity, light, etc.  But, they don't include a materials list or reference to sources where the parts can be purchased.
http://wiki.laptop.org/go/Making_XO_sensors


Radio Shack? Edmond Scientific? Parallax.com? or where? Curious people, myself included want to know. Can someone help here?


Thanks!
Caryl (GrannieB)


P.S. Here's an example of the type of info needed. This site sells a number of light sensors but they call them things like Photoresistor, Photo Transistor, Light to Frequency Converter. These are all little ones that appear similar to the one in the instructions on the wiki. How do you tell which kind you need?
I'm not someone schooled in Electronics, just an autodidact. If you are talking about a 'light sensor', this is usually a device that when exposed to visible white light will change its electrical resistance. If you are familiar with the concept of volts, current, and resistance, the basic components of Ohms Law, this device would be part of a circuit and act as a gauge for the amount of lightness or darkness in a room.  So the device would increase its resistance which is measured in Ohms when more light hits the active surface. if you buy this[0] at Radio Shack, it will contain various types of these cells. The main difference is their resistance range. Some might vary the resistance from 0 to 1,000 Ohms, some might vary from 0 to 10,000 Ohms. Or other response ranges. 
The names can vary. I first knew them as a Cadmium Sulfate Cell, they can also Light Dependent resistors. Or Photoresisitors.
As for the light to frequency converter, that is a different device.For the sake of experimentation and convience, the radioshack package might be an OK $4 investment. If you know someone who likes electronics, they might have these parts to space. Even better if you can visit a 'hackerspace' where they can help with a few parts and explanation.
I think the main use is to connect the light sensor directly to the audio-in port of the XO, which means a few wires, an audio jack and the light sensor. The 'Measure' Activity should provide a basic idea of how the sensor reacts to varying amounts of light.
[0] https://www.radioshack.com/product/index.jsp?productId=2062590
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