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Hello everybody! I need some help with something.

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cmboyl02

New Member
Hello everybody! I can't seem to find anyone to help me with my problem at my university. I am going to be in a entrepreneurship competition next Saturday and need some help putting together a circuit for our exhibit. Our company will distribute kinetic road surfaces and speed bumps that generate electricity from the braking process of vehicles, which would otherwise go to waste in the form of heat.

The exhibit is a scaled down version of the road surface that I want to act as a switch for a circuit that will light 3 leds. So when the toy car crosses over the surface 3 leds will turn on in a toy house for a 10 seconds. I want it to run off 3 to 18 volts. I have looked at a few other schematics on the site and was worried that since the time the switch is activated is so short maybe some of the designs incorporating capacitors might be ineffective. I have some bright white leds that i believe run off 3.1V.

Sorry my thoughts are so scatter brained, but sleep is not something I get to do a lot of these days. Any help you guys can offer would be more then appreciated. Thanks for reading.

Picture here:**broken link removed**
 
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bychon

New Member
One way is the ancient but versatile 555 chip. Dead simple to make a 3 second, one-shot output that happens every time the bump switch gets closed. (it's also called, "monostable"). You'd be looking for LM555 or TLC555 circuit examples. I use Mouser Electronics - Electronic Component Distributor or National Semiconductors to find this kind of thing...or I could attach a drawing...
Another way is to have the bump switch connect a voltage supply to a large capacitor, then let the capacitor discharge through 3 resistors into 3 LEDS. The "fade out" of the brightness would make the demo give the idea that power was generated by the car and slowly gets used up.
 

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Hero999

Banned
Sorry but I don't think it's a very good idea.

Any speed bump which generates power will slow the car down more.

There have be a few threads about it over the years about and most people here didn't like the idea of having to pay more for their fuel so it can be used to generate power for LEDs or something.

https://www.electro-tech-online.com...energy-from-speed-breakers-speed-bumps.41628/
https://www.electro-tech-online.com/threads/generation-of-electricity-through-compressed-air.89335/
https://www.electro-tech-online.com/threads/tell-me-which-one-will-be-better-idea.41095/

Speed bumps are not very environmentally friendly, if you want to generate clean energy then go with wind solar power etc.
 

cmboyl02

New Member
Hey Bychon, can you help me draw this up i did a couple hours of reading I'm just having trouble understanding how it works.
 

xpi0t0s

Member
Our company will distribute...speed bumps

Aargh! I hate speed bumps. I hope you go out of business, or accept bills from people with shagged suspension.

that generate electricity from the braking process

And you're not going to get round me by spouting pseudoscientific envirotard mumbo jumbo.
 

cmboyl02

New Member
Haha I think it is a terrible idea to tell you the truth, but for the class you have to push the idea and try to sell it to the judges or you fail. It is unrealistic that it would pay it self back in any amount of time and with cars pushing towards electricity and regenerative braking it will quickly become obsolete.

I could really use some help though. I'm out of my league on this one.
 

canadaelk

Active Member
My take:
1) Is it not a little late to the deadline to ask for help?
2) Many times on this forum it was stated "We do not do home-work"
3) Why do new posters only have questions? (I did not)
4) If you are "out-of-your-league" why be in it?
Sorry to be so direct
 

bychon

New Member
Let's see, battery, switch, capacitor, 3 resistors to 3 LED's. It's barely more complicatd than a flashlight.
 

cmboyl02

New Member
I know this setup makes some of you sick about how badly it was made, but this was put together with what I've learned in a short time. I could really use some help on getting the appropriate values in there.

What is the output voltage of the capacitor is it 6.3 volts no matter what?
Is there anyway to make the capacitor drain completely with out dimming the diodes out so slowly?
Any suggestion to make this thing work better?

It works and i am fairly satisfied with it after an afternoon of work, but i'm sure it could be better with some help.

**broken link removed**
 

bychon

New Member
Capacitors don't output voltage until after you've put some in, and then, they still don't convert it to the maximum rating on their label, only the amount you put into them.

The circuit is supposed to go: Battery, switch, capacitor, then the other end of the capacitor goes back to the battery, all in series, and the + on the capacitor must be connected to the + on the battery when the switch closes. Then you put a resistor from the capacitor + to an LED which is connected to the - of the capacitor. You can add more resistor/diode circuits in parallel to the first one. You can add a resistor or 2 from + to - of the capacitor to get it to drain quicker. The problem here is that you have not named a battery voltage or size, so the resistors can not be calculated.
 

bychon

New Member
The capacitor is not rated to survive that voltage. If you get the right capacitor, 9 volts minus 3.1 volts is 5.9 volts. 5.9 volts divided by .02 equals 295 ohms. Use 330 ohm resistors to let .018 amps flow through each LED.
 
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