question for electrical minded

[stuee147]

ok so iv made a 6 volt lighting system with a 6v motorcycle battery and to keep the battery topped up iv fitted a dynimo. the problem i have is that if i leave the dynimo conected to the battery when im not useing it it discharges the battery over night.
i know there is something like a realy or something that sort of only alows the current to flow in one direction, but for the life of me i just cant remember what it is called.
so anyone out there know ?

also along the same sort of lines i seem to remember many moons ago playing with LED lights and im sure i remember using an LED as this sort of one way voltage regulator thingy and it worked well with the added bonus of having a charge light so i knew when it was charging the battery.
but it was so long ago i cant recall if it was just a LED or if i made some form of regulator cirket.

i hope some one out there can work out what im on about and how i need to do it lol

stuee

 

[midlife]

Rectifier diode springs to mind from o level physics 1976 ?

Shaun

 

[stephec]

Diodes only let currency flow one way, that's what an led is.

 

[cosmicbike]

A diode is why you need, allows current flow in one direction only. You may well get away with just an LED..

 

[stuee147]

i was thinking a LED would do it but i wasnt entiely sure i think i might play with some LEDs and see what i can come up with to start with i put an inline fuse that i removed when not in use, and at the moment i have conected a switch to cut off the dynimo but i have forgot to flick the switch a few times

 

[G3CWI]

An LED is a diode (the clue is in the name). However, it is not the right sort of diode for this application. A better choice would be:

http://www.ebay.co.uk/itm/like/3003...1=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108&ff19=0

What you need depends on the characteristics of your system but this diode would be be a good start.

 

[User33236]

Bear in mind that a diode, in forward bias, will drop around 0.7v across it. What is your dymano putting out?

 

[raleighnut]

Don't dynamo's put out an AC current.

 

[User33236]

A dymano creates DC, an alternator creates AC.

 

[TVC]

Don't dynamo's put out an AC current.

Dynamos are DC generators, basically they are just like DC motors using a magnet to excite a coil.

 

[raleighnut]

According to Sheldon hub 'Generators' wrongly called Dynamos are AC devices

http://www.google.co.uk/url?sa=t&rc...44LQBQ&usg=AFQjCNHUHxwObZkU3IgpwtuUj1x9KBA0VA

 

[jonesy]

Yes, you need to fit a bridge rectifier if you want it to charge a battery.

 

[Paulus]

How about fitting a simple in line switch? Vehicles have the ignition switch which cuts the power flow.

 

[midlife]

I thought bike dynamos had a commutator which output DC current?

Shaun

 

[User33236]

According to Sheldon hub 'Generators' wrongly called Dynamos are AC devices

http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CEAQFjAA&url=http://sheldonbrown.com/dynohubs.html&ei=5t8iVZTNKIm4sQHv44LQBQ&usg=AFQjCNHUHxwObZkU3IgpwtuUj1x9KBA0VA

http://en.m.wikipedia.org/wiki/Dynamo