X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f
X-Recipient: geda-user AT delorie DOT com
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=20120113;
        h=date:from:to:subject:message-id:in-reply-to:references:x-mailer
         :mime-version:content-type:content-transfer-encoding;
        bh=msWIvYgszA/VOXggBsZMJ/s+9uRv5MFUad7+445wb4s=;
        b=rymUmUOE4AZAw2tv2bzj/HgSCxerpYan6PBvLdh2LQP3sqvei2j5BpeQV07fCViKcU
         c/+hOf5q9GSP7w7y58oOl0BzucUmI+Q/dRaSML0CKXE15jftmn5h/PHeh2iStJayJxlQ
         enaa7PwK73i6Squ9lCiwebTq2QslDyLBKp+GXltHTSxaSsQrbx6YuBffxLzVnvkZ6hy+
         JiwkF3D7SwzUPYJBAIsXPhBLm0pWu8jECqmf5m6RMa9nS+usd/TA0RMVKq0ARNv5Q7cy
         os3m6llWw0auzTQY97yYF2bm4AKFMSchkRBwWw67R3Spw2JML3Bko4VPBHttjSPr2Otr
         A8wg==
Date: Fri, 16 Mar 2012 16:59:29 -0400
From: Vanessa Ezekowitz <vanessaezekowitz AT gmail DOT com>
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] Daughter's Science Fair
Message-ID: <20120316165929.07979000@rainbird>
In-Reply-To: <141573b.10133.1361cd30be4.Webtop.22@optonline.net>
References: <141573b DOT 10133 DOT 1361cd30be4 DOT Webtop DOT 22 AT optonline DOT net>
X-Mailer: Claws Mail 3.7.9 (GTK+ 2.24.6; i686-pc-linux-gnu)
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
X-MIME-Autoconverted: from quoted-printable to 8bit by delorie.com id q2GM0aF7031862
Reply-To: geda-user AT delorie DOT com
Errors-To: nobody AT delorie DOT com
X-Mailing-List: geda-user AT delorie DOT com
X-Unsubscribes-To: listserv AT delorie DOT com
Precedence: bulk

You guys are missing one of the fundamental ideas for this kind of project:  a chopper circuit.

Connect a few batteries, a switch, the coil of a low-voltage relay, and the "normally closed" switch in the relay in series with one of your coils (your primary) on the nail:

battery -> relay coil -> relay normally closed switch -
-> your power switch -> your primary coil -> back to battery

Connect the other coil (your secondary) on the nail to your light bulb (or better, an LED).

When you close the switch, assuming the batteries add up to enough voltage, the relay will start cycling rapidly, "chopping up" the DC and inducing something not too different from an AC voltage in your primary coil.

That should, in turn, induce a voltage in your secondary and light your bulb/LED/whatever.

Yes, it'll wear the relay out after a while, but its not like this needs to last more than a couple of days anyway.

-- 
"There are some things in life worth obsessing over.  Most
things aren't, and when you learn that, life improves."
http://digitalaudioconcepts.com
Vanessa Ezekowitz <vanessaezekowitz AT gmail DOT com>