Dynamo Capacitor Design Problem

Loven

Hi all

Im a 3rd year industrial engineering student and im required to design an innovative means of harnessing energy. My project revolves around harnessing the rotational motion from 4 university turnstiles to electrial energy to be stored in a capacitor with a diode in series. the energy collected during the day will be used for emergancy lighting above the turnstile. I know the amount of energy is minute. i will also use gears ad gear ratios.·Is this a viable idea. if not, how can i improve it? And what electrical components will i need for the circuitry? Any feedback will be much appreciated. Can dynamos operate bi-directionally ie suppose a person enters and exits through the same turnstile.will the·dynamo charge the capacitor in each case?

PS I have a brief knowledge of electronics so please keep it simple or explain any technical terms. Thanks. This design project is a purely theoretical one, and it does not require me to physically build the sytem.
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stevenmess2004

Sounds doable. But you will need fairly large capacitors. You would probably be better off using a battery as it will be cheaper, smaller and take longer to self discharge. It will probably also be easier to charge than a cap (capacitor).

Before you get too far do some basic energy calculations to check if you will get enough energy to power the light for long enough.

For the circuit you will need some kind of charger for the battery or cap and something to get the right voltage for you light.

The dynamo should be able to work in both directions if you wire it up properly.

What, not build the system?? There goes all the fun!

As this is for uni I probably shouldn't say much more. Google will be your friend.

whicker

oh bother,

if you say "This design project is a purely theoretical one, and it does not require me to physically build the system", then what do you need our help for?

I love blue sky thinking, anything goes. The system I would design would be so efficient (and expensive) that they'd never recoup the cost in energy savings versus just plugging the lights in. :P

ChrisP

My approach would be a very small, say 4" square, or the largets size that would fit anyway, surplus 3 phase brushless servo motor. Easily mountable, readily obtainable for a very low price, also a ready built dynamo, permanent magnet and very very efficient·as an alternator when back driven·for something that can be picked up for scrap.



Remember, were talking emergency lighting here, not a reading lamp or floodlight so the light output doesnt have to be very high.

3 Phase brushless motor with the phase leads conencted to a 3 phase bridge rectifier (capture positive and negative voltage) gives you a DC output voltage, motor speed, gearing etc will determine voltage output. However since the current output capability is relatively low I wouldnt bother investigating a voltage regulator. Use the load from charging the backup battery as a voltage limiter, a comparator circuit sampling the voltage would disconnect the battery from the generator set once the battery reached a fully charged state. For lighting using one of the 1, 3, or 5 watt LED's would give you a substantial amount of light for very little current cost.

One thing you might investigate from a practicality standpoint would be looking into switching your generator into a dead load (resistor etc) when it switched away from a fully charged battery to avoid the friction on the turnstile from suddenly dropping off or changing when it switches out.

Beau Schwabe

ChrisP,

"surplus 3 phase brushless servo motor" - The right Stepper motor might work also, and provide more phases (<- better energy transfer)... I'd scope out the local "Assisted mobility" store and educate myself on wheel char motors.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

ChrisP

Beau,
Thanks for the heads up, I'll have to look at those. I work with 3 phase brushless every day so they're very easy for me to pick up even current models pushing 90% efficiency. Never realized that steppers may do even better!!