• Re: Simple useful circuits

    From Peter Sotropa@21:1/5 to Tabby on Tue Feb 15 15:27:03 2022
    On Monday, 30 November 2015 at 02:38:25 UTC-7, Tabby wrote:
    On Sunday, 29 November 2015 20:48:46 UTC, Rich S wrote:
    On Saturday, November 28, 2015 at 4:17:34 PM UTC-5, tabb...@gmail.com wrote:
    On Saturday, 28 November 2015 18:30:33 UTC, Tom Miller wrote:
    <ri...@engineer.com> wrote in message news:590a8c4a-7f21-47b2...@googlegroups.com...
    On Saturday, November 14, 2015 at 6:56:24 PM UTC-5, tabb...@gmail.com wrote:
    I'm looking for ideas for things to make in the 3rd world from electronic
    junk. What simple circuits have you found useful? Whether as tools or end
    products. Have already done minimal versions of audio amp, sig gen, alarm,
    voltmeters. I've a list of ideas but I'll bet you have some interesting
    ones I've not thought of.

    Here's a purely electronic device... simple, life-saving -- a fire alarm:

    Developing world uses a lot of open flames, so risk of fires is very high.

    A CO detector might serve well also.

    Cooking fire fumes are a big cause of death. But is there a technology to detect CO that can be made for 10 cents a piece?


    There's a plastic film that darkens (turns orange) when exposed to CO. It's not the most sensitive technique, but may be good enough, especially if it is near the potential source. A simple electronic circuit to detect the photo-optic change would be

    A low-battery warning would have to be included too (though, if the battery is the most expensive part, then just discard the whole thing with a fresh unit).

    Another issue is that the film could get dusty, dirty, aged (after some amount of CO exposures, the film will not return to fully clear) leading to false alarms. So it has to be designed to keep the dust out. The aging may not be a problem if its
    replaced after a time and/or after any alarm event.

    I do not know if anyone has designed this into a product yet!

    Google so far shows lots of experiments on films, but nothing buyable.

    You might be interested in our patent prototype. http://lightswitchracing.com/Receipt%20of%20Patent.pdf

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