Photosensor-Brake System for a Small Plastic Car

[DonAlejandro]

Hello,

I am attempting to expand my physical understanding of some engineering principles I’ve learned during my first semester of ChemE. I am making a small plastic car that will be propelled with a weak fan. I am attempting something similar to a ChemE project car. Is there a way I can use a photo sensor to stop the front axel from spinning? Perhaps another approach would be to brake the circuit between the small battery and the fan it powers. How should I approach this? I assume I’ll have to use an arduino or raspberry pi, which I will have to learn to program. Thanks.

 

[anorlunda]

Yes, you can cut off the power to the fan. Yes you can make a brake that is triggered by a photo cell.

Are there some hard requirements? For example, the car goes 5 mph and we can sense the wall 2 inches away, the car must stop before hitting the wall.

Or are you just looking for the simplest way to stop the car without any hard stopping distance requirement?

 

[DonAlejandro]

Thank you for your response. The requirement is that the car comes to a stop at a given random distance less than ten or so meters. My plan so far is to repeatedly use a color-changing chemical reaction (an iodine clock) to cause the car to stop. With collected data I can predict Acid/Base amounts. I just don't know how to use a photosensor to do anything. If the goal was to cut the power to the fan, how could I do this?

 

[anorlunda]

Amazon list more than 1000 hits for "photo sensor switch", some as cheap as $3.28 I'm sure that the manufacturer's datasheet for any of them will show a sample circuit.

Since your electronic skills sound pretty basic, it would be best to buy as much as you can and build as little as possible.

p.s. I don't understand anything you said about the chemical aspects of this project.

 

[Baluncore]

It would be possible to detect the change of solution optical properties with a simple photo detector.

If the challenge is to stop the car at a specified distance then you need to have accurate control of distance, or of both speed and time. Knowing the temperature, your chemical clock reaction may give you accurate time, but velocity will be more variable. You would need to also regulate speed somehow.

What are the specified rules that you must follow?