Transitioning from the classroom

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In summary: However, it is not as simple as just finding the power limitations of a 5mW LED and supplying that amount of current. You would need to be aware of the current draw of the LED, the voltage of the battery, and the resistance of the LED.
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sherrellbc
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I was thinking lately of taking a few battery-operated devices and converting them such that they could run off other energy sources (like outlets). But, I was wondering what concepts should be taken into consideration?

For example, I have a fan that runs off of two D 1.5V batteries; this is all I know. I do not know the current draw from the batteries (and consequentially the power limitations of the fan's internal circuitry). I know the limitations of the batteries, in terms of mA-h, but that is all and gives you little information. I was thinking perhaps attempting to come up with a Thevenin Eq. circuit and going from there, but with the electric motor to turn the fan I am not sure where to start.
--I was thinking 5v from an arduino, and then a transistor for current drive. Although, I am not sure how much current.

Or perhaps I want to run a small DC motor that I have. The only information on the datasheet is that it's 1.5-3.0V motor with 300mA draw at no load. What about when there is a load? Power dissipation limitations? Do you just arbitrarily design a circuit, perhaps a transistor, with an output of ~500mA at 2V?

Similarly, I was looking at converting a laser-pointer. The device uses three 1.5V batteries and the specifications are ~<5mW. This gives me a starting point much better than the other two projects mentioned above, but still leaves some uncertainty. Is this circuit as simple as using the power limitations of 5mW, and voltage of 4.5V, designing a circuit that will supply ~1.11mA? I have never seen an LED that draws such low current.

I am fully able to work through problems with the constraints and requirements given, but how to do you figure out such constraints to begin with?
 
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To answer your last question, how we figure out the constraints: We look at the datasheets and calculate from there :) The datasheets will most likely show you the "Absolute Maximum Ratings" which provide you with the knowledge of the absolute constraints, and then you design from there.

The fan:
If the batteries are in series and they thus provide 3 volts, the next step would be to figure out the current draw. If you don't have a measuring apparatus, or the datasheet, the only other way I can imagine doing it would be to measure the time it takes for the fan to use up all the juice for the fully charged batteries.
if they have for example 10 mA-h and it takes 1 hour, then you know that the fan has been drawing 10 milliamps. this would be an experimental estimate of the current draw. if you're not going to change the voltage, then you would be able to model the fan as a fixed resistor.

The DC motor:
The current draw would be greater when you have it loaded. The maximum power dissipation is not possible to know unless it tells you on the datasheet. So here you would need to be on the safe side. I would believe that supplying 400mA would still not be a problem. However, think about this. The current drawn by the DC motor provides a torque, given by the "torque constant" of the motor. If you want to design a driving circuit for the motor, you would need to make sure that the transistor and other components can handle the current draw.

The Laser pointer:
If you want to replace the battery, the yes.
 

What does it mean to "transition from the classroom"?

Transitioning from the classroom refers to the process of moving from a traditional classroom setting to a different learning environment, such as online learning, a research laboratory, or a corporate training program.

What are the benefits of transitioning from the classroom?

Transitioning from the classroom allows for a more flexible and personalized learning experience. It also provides opportunities to gain practical skills and real-world experience in a specific field of study.

What are the challenges of transitioning from the classroom?

Some challenges of transitioning from the classroom may include adjusting to a new learning style, managing time effectively, and maintaining motivation and self-discipline without the structure of a traditional classroom.

How can I prepare for a smooth transition from the classroom?

To prepare for a smooth transition from the classroom, it is important to research and understand the new learning environment, set clear goals and expectations, and develop good time management and study habits. It can also be helpful to reach out to others who have made a similar transition for advice and support.

What resources are available to help with the transition from the classroom?

There are various resources available to help with the transition from the classroom, such as online tutorials, workshops, and support services provided by the new learning institution. It can also be beneficial to seek guidance from teachers, mentors, or peers who have experience with the new learning environment.

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