Photocell Bonus

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Re: Photocell Bonus

Post by DeltaHat » December 21st, 2009, 12:28 pm

Absolutely not.
Laser levels, pointers and other laser devices are intended to be operated under the control of a human operator at all times. They are not meant to be attached to a somewhat independent mechanical device such as a robot operated in a room filled with contestants, judges and spectators who are preoccupied with other activities.
Lasers must be human controlled. Mission possible machines are autonomous by design. Therefore, they cannot include lasers.

Source: http://soinc.org/lasers
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Re: Photocell Bonus

Post by teamcosmos » December 29th, 2009, 9:18 pm

can you use a single pnp transistor in the circuit with the photoresistor - this would make it possible to run motors etc easily but still controlled by the light hitting the photoresistor. never mind i just read the rules clarification ( no trasistors ) :(

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Re: Photocell Bonus

Post by fleet130 » December 30th, 2009, 12:11 am

cypressfalls_Robert wrote:could the light source of the photoresistor circuit mentioned above consist of a laser by any chance?
http://soinc.org/lasers wrote:All lasers are required to have a safety label stating the class they fall under. Lasers missing the required label will not be permitted. Due to the difficulty of verifying power output, only commercially assembled laser devices may be used.

Image
(actual label may vary)

Class 1, 2 & some Class 3a lasers are labeled with a "Caution" and the possibility for injury is minimal. They can be allowed without question provided contestants avoid indiscriminate exposure to other contestants, judges or spectators. Careless/indiscriminate use may be grounds for disqualification.


Image
(actual label may vary)

Some Class 3a & all Class 3b lasers are labeled with a "Warning" and there is a definite, though small, possibility for eye injury. These are allowed if they are mounted in a fixed position on a stationary device.

They may not be used on mobile devices such as robots and vehicles. Contestants must take fail-safe precautions to eliminate the possibility of accidental exposure to the eyes of judges, spectators, contestants and other people in the room. Shielding must be provided to insure the laser beam cannot exit the boundaries of the device. Accidental eye exposure is proof that proper precautions have not been taken and the team must be disqualified if it occurs.
The implication is that lasers with a "Caution" label may be used anywhere, as long as precautions are taken to prevent eye exposure. Any eye exposure, even accidental, is proof of careless/indiscriminate use and contestants may be disqualified if it occurs.

Lasers with a "Danger" label may not be used on mobile devices, but they may be used on fixed devices such as with Mission Possible. The laser beam must not be allowed to exit the boundaries of the device. Any eye exposure must result in disqualification.

Bear in mind that all laser devices also contain other electronic components such as transistors and integrated circuits to control the current to the laser diode. If these electronic components are prohibited, the laser would violate the rules.

As always, the only way to be sure is to pose the question to the judges of the tournament you will be competing in.
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 gh » December 31st, 2009, 4:26 pm

The laser diode itself would be pretty difficult to justify as legal by the 2010 rules, let alone the support electronics.
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Re: Photocell Bonus

Post by DeltaHat » January 1st, 2010, 9:44 pm

gh wrote:The laser diode itself would be pretty difficult to justify as legal by the 2010 rules, let alone the support electronics.
Good point, given the whole ban on transistors.
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Re: Photocell Bonus

Post by rocketchicka » January 8th, 2010, 1:29 pm

can someone tell me how to set up a photocell? I tried setting them up with a motor, but nothing's happening. Do need batteries or something? :?:
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Re: Photocell Bonus

Post by cypressfalls Robert » January 8th, 2010, 3:27 pm

rocketchicka wrote:can someone tell me how to set up a photocell? I tried setting them up with a motor, but nothing's happening. Do need batteries or something? :?:
p-----------------X----Battery----X------------|
p-----------------X------------------------------|Motor

p= photocell
X= joint
-= wire?
|= motor

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Re: Photocell Bonus

Post by bugsrcool » January 10th, 2010, 10:00 am

Use the setup on the first page under the Wiki. It works perfectly on some motors. Some motors have way too much current and too little resistance to work with a photocell. We tried several motors until we found a couple that worked well under the amount of photoresistors we put in and the light source. None of them worked at full power because there was always some resistance still left in the photocells even under some very bright lights.
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Re: Photocell Bonus

Post by Dark Sabre » January 10th, 2010, 11:05 am

I updated both the fist post in this thread and the wiki diagrams to be more clear about what design should be used (remove all references to that random resistor), reworded some stuff that has been made irrelevant because of the rules clarifications, and hopefully made it more obvious that a battery was required in the circuit.

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Re: Photocell Bonus

Post by fleet130 » January 19th, 2010, 2:41 pm

I was able to get the motor in this solar racer kit to spin with just the light from a common 2-cell mini-maglite.
ImageImage
[Click Photos to Enlarge]

These kits are pretty expensive (in my opinion), but it gives you some idea of the size of the motor. You could replace the photo-voltaic photocells with photo resistors connected in parallel and a battery as explained above. These tiny motors are often available from surplus liquidators. I have bought them from Radio Shack. They were being sold as replacement motors for the small re-chargeable radio-controlled cars.

Kits from Tamiya, such as the "Blue Eagle" and "Honda Dream", have motors that are about the same length and are about twice the diameter.
Image
[Click Photo to Enlarge]

As a much less expensive source you might try googleing for somthing like "surplus pager motor"
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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