Need a transistor-less, IC-less photocell circuit

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Yerry
Posts: 40
Joined: Wed Mar 02, 2005 1:01 am
Location: Kentwood, MI USA
Contact:

Re: Need a transistor-less, IC-less photocell circuit

Post by Yerry » Sun Nov 15, 2009 7:16 pm

Thanks for all the help! Leaning towards the many-CdS-cells-in-parallel route.

One unfortunate thing; due to "rules lawyers", everything is spelled out to an extreme-- even commas matter. Also, since I used to be a National Supervisor for this very event, anything my kids do is scrutinied to an extreme, which means I have to be very careful as to what I approve. Unlike other coaches, I don't touch their stuff (proof: look at their soldering, er, welding), so it all needs to be do-able.

Okay, here are all the applicable rules:

10V dc max, source AND components (it took two years, but they finally banned our use of choppers)

No diodes, transistors, microprocessors or other solid state, and no 'modules" containing such.

No motors may be running before the device starts.

"Activate a photocell which will provide the power to operate a motor, which leads to the next action." [this is the actual task]

+++++++
So, any "sticky wickets" that might crop up: the "no motors running beforehand" and a requirement that all steps be in sequential order A -> B -> C ->D etc., means that this thing has to turn the motor ON.

Also, the motor has to do "something" to start the next step, which means that, with a low-current motor, it can't be required to do much, like push a ping-pong ball.

Not sure if "provide the power to operate" means a relay can't be used. There's been no "chat" about it amongst the event supervisors yet (I run the event in one state). Personally, I say they CAN be used.



Looking for CD spindle motors as I type,
Yerry

User avatar
CeaSaR
Posts: 1752
Joined: Sat Nov 08, 2003 1:01 am
Location: Phoenixville, PA USA
Contact:

Re: Need a transistor-less, IC-less photocell circuit

Post by CeaSaR » Sun Nov 15, 2009 10:08 pm

rules laywers wrote:No diodes, transistors, microprocessors or other solid state, and no 'modules" containing such.
A photocell is a solid state device, so technically anything containing one would be in violation of the rules.
Hmm... quite the paradox, eh? :mrgreen:

CeaSaR
Hey, what do I know?

User avatar
Lenp
Posts: 1453
Joined: Thu Oct 26, 2006 8:11 pm
Location: Maryland
Contact:

Re: Need a transistor-less, IC-less photocell circuit

Post by Lenp » Mon Nov 16, 2009 4:34 am

Ceasar...

I doubt that a photo resistive cell could be classified as a solid state device, no more than a common resistor would be. These were around long before 'Solid State' was a buzzword. Probably to put a label on it would be to call it an 'variable passive' device much like a potentiometer or variable capacitor. Photo transistors, scr's and the like would be solid state.


Yerry...
Since they don't specify 'how much light' is necessary how about a magnifying glass focused on a thin string that when burns releases a switch to close and start the motor? A sunlamp may be sufficient! :grin:

Len
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

User avatar
CeaSaR
Posts: 1752
Joined: Sat Nov 08, 2003 1:01 am
Location: Phoenixville, PA USA
Contact:

Re: Need a transistor-less, IC-less photocell circuit

Post by CeaSaR » Mon Nov 16, 2009 11:04 am

TheFreeDictionary.com
Medical-Dictionary @ TheFreeDictionary.com
Merriam-Webster.com
Dictionary.reference.com

Just on the first page of a Bing search for ' definition of "photocell" '.

A LDR, or CDS cell are resistive in nature, but are still solid state devices that vary, usually negatively, when
exposed to light. As tough as the rules laywers have been made out to be, they should be more specific in
their description by specifying what type of photocell to use.

Nitpicking the nitpickers,

CeaSaR
Hey, what do I know?

User avatar
Lenp
Posts: 1453
Joined: Thu Oct 26, 2006 8:11 pm
Location: Maryland
Contact:

Re: Need a transistor-less, IC-less photocell circuit

Post by Lenp » Mon Nov 16, 2009 11:25 am

And so, what about the magnifying glass approach~
Rube would be proud!
Len
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

User avatar
CeaSaR
Posts: 1752
Joined: Sat Nov 08, 2003 1:01 am
Location: Phoenixville, PA USA
Contact:

Re: Need a transistor-less, IC-less photocell circuit

Post by CeaSaR » Mon Nov 16, 2009 12:45 pm

How about the cascading avalanche effect where the first light magnifies and burns through the string
which then allows it to be automatically repositioned to shine on 1 or more LDRs which then turn on more
lights which shine on more LDRs which then are reduced enough in resistance to turn on the motor. Put
a propeller on the motor and you can make it do something with wind power.

If you make it turn on a CD player (CD spindle motor), you could make it an audio driven event. :shock:

Gotta love Rube!

CeaSaR

Yerry,

You'll have to let us know when we can expect the news coverage of the event. We have to see what
everyone came up with and who won, etc.
Hey, what do I know?

Yerry
Posts: 40
Joined: Wed Mar 02, 2005 1:01 am
Location: Kentwood, MI USA
Contact:

Re: Need a transistor-less, IC-less photocell circuit

Post by Yerry » Wed Dec 09, 2009 10:07 pm

Using 6 D cells (9V), a 1.5v pager motor, some photocells on sale from Electronics Goldmine and a breadboard it was a breeze for Johnny Boy to figure out the circuit. Took him more time to solder some wire to the tiny pager motor that it did to set up the photocells.

three photocells in parallel dropped 6-7V while the motor dropped 2-3V. Motor had a vibrator weight (off-center on the shaft) and it hopped all over the place. However, the photocells got hot ans started acting flaky. So, JB added a 47-ohm resistor in series with each photocell and increased the photocells in parallel to 8. Works great, 100% reliability. Motor hops and slides off the angled board it sits on, and falls about 10" until it hits the end of the supply wires, which are looped around a smap switch, transferring action to he next step. Kid's pretty sharp-- after two years of colossal failures (at other events), he's building like gangbusters, everything works the forst time, and (best of all) I never have to remind him to clean up after himself! Now if I can get the other 30 slobs to do the same, and they're not even builders. . . .

First tournament (an invitational) is in mid-january. the big ones, Regionals and States (the ones that count) are in March and may, and pictures won't get put up until after. Competition is pretty tough here. . . .

Thanks from Johnny Boy and I for your help.

Yerry

Post Reply

Who is online

Users browsing this forum: No registered users and 35 guests