Mission Possible C

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nadroj
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Re: Mission Possible C

Post by nadroj » December 14th, 2013, 5:31 am

Wondering if transistors are allowed according to this years rules. Can anyone help me on that?

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Re: Mission Possible C

Post by olympiaddict » December 14th, 2013, 7:50 am

They are not.

+1 on hoping the sample ETL will be posted soon.

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Re: Mission Possible C

Post by GreatMindsThinkALot » December 16th, 2013, 5:15 pm

I know this was mentioned before but...

I know rule 3i. ("Only wires, batteries, photosensors (e.g., photovoltaic cells, photodiodes, photoresistors, phototransistors), light bulbs, LEDs, homemade solenoids, switches, and up to three motors may be used in the device. No computers, integrated circuits or other electric components are allowed.") excludes transistors. But without transistors, isn't it almost impossible to practically use any photosensors?

olympiaddict
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Re: Mission Possible C

Post by olympiaddict » December 16th, 2013, 6:00 pm

It's tough, but it's still possible to use phototransistors and photovoltaic cells.some phototransistors are rated for some decent amounts of current, and photocells can generate enough power to drive very small motors. Alternatively, you can have the sensor power a homemade relay, which connects a more powerful circuit.
It's gonna be pretty tricky to use photoresistors though.

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Re: Mission Possible C

Post by Uncle Fester » December 16th, 2013, 6:59 pm

A couple of years there was a similar ruckus over using photocells without transistors.

Here's a freebie from The Old Man, in non-electronic, non-math terms:

1) Find photocells with a relatively LOW "ON" resistance. 40 Ohms is the lowest I've found at discount prices recently . Get a bunch of them.
2) Use 2, 3, 4, or 20 IN PARALLEL to get the total resistance down (math is "typical resistance" divided by the number of photocells in parallel). Parallel, not series. In other words, one side of ALL photocells connect together at one point, and the other remaining wires connect together. Kind of like a ladder. DON'T WORRY ABOUT OFF RESISTANCES.
3) If the photocell array is in series with "something", like a HOMEMADE relay (read the rules), and both have resistances of 40 ohms, voltage divides in a simple ratio, and relay gets half the supply voltage. Not enough voltage to work? Keep adding photocells, and the relay voltage will increase.

BEWARE: Photocells are typically rated for 1/8 or 1/16 Watt. That's close to "zero". A blown photocell USUALLY emits a Gosh-Awful smell. Troubleshooting can be difficult, so best to overdo the number of photocells. If you don't have enough to share the current, what'll happen is the photocells will pop one by one, reducing available current, until current drops enough to where there's not enough to pop more photocells-- or power a relay.

And in other news, in Indiana, I allow reverse transfers, meaning stopping light, electricity, reactions, etc to start a transfer is okay. Been doing this for almost twenty years. It's been legal pretty much everywhere else, so it's not like I'm some kind of rebel. . . . Remember, "conservation of energy" hasn't EVER been mentioned in the rules for Mission, EVER.
Uncle Fester, Maker & Fiction Science Writer

The Misadventures of the Electric Detention
The Revenge of the Electric Detention
The Curse of the Electric Detention
>> Three full-length adventures, 26 short stories and counting!

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Re: Mission Possible C

Post by Uncle Fester » December 16th, 2013, 7:05 pm

Umm. . .

Photocells and photoresistors are the same thing. Cadmium Sulphide, resistance varies by photon contact.

Photocells don't "generate power". They dissipate it, or at least they do until they blow.

Phototransistors have polarity; watch out. They'll also blow at the slightest wiring mistake without making a sound, and frequently without a smell.
Uncle Fester, Maker & Fiction Science Writer

The Misadventures of the Electric Detention
The Revenge of the Electric Detention
The Curse of the Electric Detention
>> Three full-length adventures, 26 short stories and counting!

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Re: Mission Possible C

Post by Flavorflav » December 17th, 2013, 1:41 am

Uncle Fester is right, of course. With the old mission, we used two photocells (i.e., photoresistors) in parallel to trip a relay without too much trouble. We just had to put them and the light bulb into a small box so that they started in the dark.

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Re: Mission Possible C

Post by olympiaddict » December 17th, 2013, 4:16 am

sorry, when I said photocell I fell under the same questionable terminology as the original rules had used. my mistake. replace photocells with photovoltaic cells if you like.

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Re: Mission Possible C

Post by nadroj » December 17th, 2013, 5:56 am

Is it required for motors to be turned off? Also, has anyone had experience using an infrared sensor from an infrared switch as an energy transfer?

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Re: Mission Possible C

Post by gesturallyimprobable » December 17th, 2013, 10:05 am

Sorry if this has been asked already, bu if you move something to unblock a light bulb and have the light trigger the next action, would this count as a transfer of m --> ems? Or would it not be any transfer at all?

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