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CO2 controller as designed by Gary Bishop

Hello.  Recently I sent this e-mail to Mr. Bishop himself, but I have not
received a response yet.  Perhaps some other EE people have built this
controller and could help me out, so here is the original message (yes
Gary, I _am_ a little impatient I guess :-): (so just pretend this message
is to everyone...hehe)

Hello!  I've recently taken up the task of building your design of a CO2
injection -- Tom Szymkiewicz (mrtom at wpi_edu)  Massachusetts Academy of
Mathematics and Science WPI - Worcester Polytechnic Institute USA
controller.  I am not an EE person, but a future physics major, and have
WWW: http://www.wpi.edu/~mrtom almost no experience or knowledge about
circuits, only a little from an introductory physics class and some books
that I have. I managed to solder everything, which later I learned to be a
mistake, because I could have used a bread board.  The point is that I
have checked everything and it seems to be in accordance with your
diagram.  But it doesn't work! (how could you have guessed? ;-)  I used
elements with the same parameters as you provided, with the exception of
the photocell from Radio Shack.  The particular one you used has been
discontinued by Radio Shack and I was forced to buy some 'assorted
Cadmium-Sulfide photocells', cat. no. 276-1657.  I'll desribe what
happened: 

1) I connected one of the leads from a 12.6V AC transformer to the
left-most lead of the 5V fixed regulator.  2) I connected all ground leads
to the other lead of the 12.6V transformer...is this my mistake? Shouldn't
I connect it to something that has a potential of 0 with respect to the 5V
in the circuit and not something that varies?  This seems to be a pretty
dumb mistake to me, but again, I have no experience or training in
electronics...only physics. 3) Nothing happened...isn't the green LED
supposed to light all the time? I tried covering the photocell and
uncovering it, and nothing happened. 

Is the current entering into the circuit supposed to be DC in which case I
would have to build a four-diode device described in one of my books to
convert the AC to reasonable DC? 

Yet another question...about the relay.  It looks like this:  [under-side
view]

1 4 ' 2 3 '

Am I correct in connecting leads 3 and 4 to the ends of the diode?  Are
leads 1 and 2 connected to the solenoid? 

Even more questions:  Can I replace the 500 microF capacitor with a 470
microF? Could you also please explain in non-EE terms where to connect the
power supply to? 

Maybe I will actually learn something from doing this project.  I would
greatly appreciate your help and I will be sure to let you know, if it
ever works ;-), about it's performance so that you have the requested feed
back.  Thank you in advance. 

-- 
Tom Szymkiewicz (mrtom at wpi_edu)  
Massachusetts Academy of Mathematics and Science 
WPI - Worcester Polytechnic Institute USA
 
WWW: http://www.wpi.edu/~mrtom