Photocell Bonus

Balsa Man
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Re: Photocell Bonus

Post by Balsa Man » January 25th, 2010, 10:41 am

Balsa Man wrote:THanks for being polite, too-- I get enough yelling and name-calling at work.
Of course. Coming from The Man, it really had me worried, hence my.....somewhat exhaustive :"operative words".....diatribe (when, but had I checked, it was nailed by the 1/16 clarification. Thanks
Uncle Fester wrote:I doubt any sup cares how old a box is. After all, it's supposed to be imaginary.
Thanks, also; made sense to me it wasn't/shouldn't be an issue, but.....the devil is in the (rukes) details. It is a cool box.... Now the kids just need to finish getting all the new stuff installed.
Len Joeris
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yoyo1299
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Re: Photocell Bonus

Post by yoyo1299 » February 5th, 2010, 6:39 am

I definitely need help...

This is my current setup:

4 AA's --------- 4 photo receptors in parallel -----------a 1.5-3v motor (yeah i realize i'm putting a lot more voltage in the circuit than i should) --------- Back to battery pack

I am using a flashlight that runs off of 4 c cell batteries. Nothing works :/ Should I try more batteries in my circuit? I have three different motors to try from a Super High Speed motor (9v), the one i'm using currently, and a larger motor, can't find the details about it. It's quite a powerful motor tho.

All of my circuity is from radio shack. I've followed everyone's instructions.

Help?

Thanks!

cypressfalls Robert
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Re: Photocell Bonus

Post by cypressfalls Robert » February 5th, 2010, 1:53 pm

yoyo1299 wrote:I definitely need help...

This is my current setup:

4 AA's --------- 4 photo receptors in parallel -----------a 1.5-3v motor (yeah i realize i'm putting a lot more voltage in the circuit than i should) --------- Back to battery pack

I am using a flashlight that runs off of 4 c cell batteries. Nothing works :/ Should I try more batteries in my circuit? I have three different motors to try from a Super High Speed motor (9v), the one i'm using currently, and a larger motor, can't find the details about it. It's quite a powerful motor tho.

All of my circuity is from radio shack. I've followed everyone's instructions.

Help?

Thanks!
Read the Photoresister Circuit Wiki
after that try putting the right voltage with your circuit

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Re: Photocell Bonus

Post by Dark Sabre » February 5th, 2010, 1:57 pm

yoyo1299 wrote:I definitely need help...

This is my current setup:

4 AA's --------- 4 photo receptors in parallel -----------a 1.5-3v motor (yeah i realize i'm putting a lot more voltage in the circuit than i should) --------- Back to battery pack

I am using a flashlight that runs off of 4 c cell batteries. Nothing works :/ Should I try more batteries in my circuit? I have three different motors to try from a Super High Speed motor (9v), the one i'm using currently, and a larger motor, can't find the details about it. It's quite a powerful motor tho.

All of my circuity is from radio shack. I've followed everyone's instructions.

Help?

Thanks!
Do you have a voltmeter?

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Re: Photocell Bonus

Post by yoyo1299 » February 5th, 2010, 2:15 pm

Yes i've followed the Wiki.

Yes, I have a voltmeter. Should I check Ohms? I've tried that, but the reading is confusing..

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Re: Photocell Bonus

Post by fleet130 » February 6th, 2010, 5:12 pm

This is your circuit below:
Image

You didn't mention start/stop switches, but I included them as they are a good idea to keep from exhausting the batteries prematurely. The start switch is a normally open switch actuated by some previous action. It could be done manually during final prep for a run.

The stop switch is shown as a separate normally closed switch. In Practice, it is often opened by completion of the action performed by the motor. For the current action being discussed, it could be the same switch as the start switch and actuated manually after the run is finished.

With the circuit connected and both switches(if used) turned on, shine the light on the photoresistors and measure the voltage across the motor.

If it is less than what the motor needs to run, you must add more photoresistors, more light or both. You could also add regular resistors instead of photoresistors. Since the resistance of normal resistors doesn't increase in the dark, this would exhaust the batteries faster.

There are many more factors to consider, but measuring the voltage drop across the motor should compensate for most of then.

The motor should be the lowest voltage/lowest current you can find. Generally, the smaller the motor, the better. Surplus pager motors are great!
Information expressed here is solely the opinion of the author. Any similarity to that of the management or any official instrument is purely coincidental! Doing Science Olympiad since 1987!

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Re: Photocell Bonus

Post by tinytom » February 7th, 2010, 3:53 pm

Uncle Fester, not complaining, but just asking for clarification so we don't get dinged again. Our team used a photovoltaic cell to run a motor. The judges said the clarifications said a photovoltaic cell is not a photocell. (I didn't think that was the point of the clarification, btw.) We did not get points for that step. We looked at a number of definitions of 'photocell' online and checked a number of online dictionaries. Many of them said photocells are photoresistors and some also said they could be photovoltaic cells.

What is your call? Is a photovoltaic cell legal in Mission this year?

Thanks!
tinytom

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Re: Photocell Bonus

Post by tinytom » February 7th, 2010, 4:05 pm

Dark Sabre, I guess I should have directed that post 37 to you. Is a photovoltaic cell legal this year? If not, could you explain why?

Thanks!
tinytom

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Re: Photocell Bonus

Post by Dark Sabre » February 7th, 2010, 5:53 pm

So that clarification that you read states:
Mission Possible: Section 3.d. should read (see additions in bold): "Electric components shall be limited to batteries, wires, motors, switches, resistors, capacitors, commercial photocells (i.e., cadmium sulfide (CdS) cell, photoresistors or light dependent resistors), mechanical relays, lightbulbs, and LEDs. No computers or transistors will be permitted in the device." (11/9/09)
fleet talked about what using "i.e." there meant, at one point:
fleet130 wrote:Taken literally, the clarification allows only "cadmium sulfide (CdS) cell, photoresistors or light dependent resistors".

i.e is an abbreviation for the Latin "id est" ("that is" in English)) and includes only those items specifically listed.
Nationals confirmed that interpretation with this FAQ: http://soinc.org/node/514
The revision to Section 3.d. "commercial photocells (i.e.cadmium sulfide (CdS) cell, photoresistors or light dependent resistors" seems to only include photoconductive type photocells. Does this mean that photovoltaic type photocells (i.e. solar c...
Correct, photovoltaic cells are not allowed.
Previously, FAQs and Clarifications only officially applied to the National tournament, though states and regionals often obeyed them.
This year at least..."These Official Rules Clarifications apply to all states and all tournaments and originate at the national level." appears on both the clarification and FAQ pages.
So the above should apply to all tournaments.

So no, photovoltaic cells are not allowed at the moment. Why? Well, they just decided that was how it was going to be :lol:
The original rules left it kinda vague as to what was allowed and in the clarification process, they decided to ban photovoltaics and allow only photoresistors.

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Re: Photocell Bonus

Post by Flavorflav » February 8th, 2010, 1:41 am

Which I think was a terrible idea, BTW. A lot of teams don't even know about the clarifications on Soinc.org. As I understand it, the switch was made because they didn't think solar cells would work - so why 2nd tier people for trying? If they get it to work, more power to them (and their motor!); if not, they don't score the task. What's the problem?

Ah well, it is what it is.

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