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PostPosted: 18.05.2004 08:35 
Ok so i already know what resistors are and how they work and what they do. My question is what in the ampere equivalent of one volt. like i want to make something go from 12 volts to three, what kind of a resistor would i use? You can reply to this, but since I am not a registered member, could you please send it to udamnpunks AT hotmail.com? I would probably find this out through some experiments with my voltage meter, but I have to go to sleep.


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PostPosted: 18.05.2004 08:37 
oh sorry i meant ohms


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PostPosted: 18.05.2004 09:10 
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Junior Modder
Junior Modder

Joined: 14.05.2004 09:19
Posts: 12
Location: Tampere
You really should read the basics of electronics... But cos' I'm in a good mood i'll try to explain.
All basic electronics is based on the great god of almighty the "Ohm's law". Ohm's law helps to determine the third value from the existing two.
U=voltage, I=current and R=Resistance
Ohm's law states:
I=U/R
R=U/I
I=U*R
So if we know for example the current and the voltage we can calculate the resistance.
To calculate the needed resistance of a circuit that "lowers" the voltage we need to know two of the components. The current and the voltage. This is hard to explain so i'll demonstrate.
If a basic Finnish man (luultavasti amis 8) ) wants to light led to his Toyota Corolla he'll calculate the circuit
Basic led needs about 1,2V to light up and needs a 20mA current. If the power suply supplies 12V we need a resistor in front of the led.
12V-1,2V=10,8V so 10,8V is the voltage that we need to be lowered. Cause the circuit is in series we know that the current flowing thru the resistor is the same that is flowing thru the led we can calculate the resistors resistance.
Ohm's law... R=U/I so -> resistance=10,8V/0,020A(20mA)=540ohms.
So we need a resistor that is 540ohms...
Hope this helps.

_________________
Elämä on ihmisen parasta aikaa....


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PostPosted: 18.05.2004 10:05 
just a quck question... is it 20mA on everyone?


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PostPosted: 20.05.2004 01:18 
Thanks. I had TRIED to read up on these stuff but when i googled resistors, i just got tutorials on how to calculate the resistance from the colored strips


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