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View Full Version : using a motor and led - problem


wardivich
09-09-2008, 12:09 AM
hi.
ive made a circuit which runs a DC motor and powers an LED. there is a switch in series to the motor.

problem;
the led is in parelel to the motor, when the motor is off, the led is on, but when the motor is on the LED is off.

i know why this happens, but is there a way for the LED to be on at the same time as the motor while using the same power sorce?

if i put the LED in series with the motor, will the motor slow down as the current is restricted?

iv'e got a feeling that there is a componant i don't know about.

any advice or suggestion would be welcomed.

thanks

Audioguru
09-09-2008, 12:26 AM
What is the colour of the LED?
If it is white or blue then it needs about 3.5V. Maybe when the motor is turned on its high current reduces the voltage across it and across the LED to less than 3.5V so the LED turns off. Then when you turn off the motor the voltage jumps high enough to light the LED.

Please attach your schematic for us to see what is causing the voltage to change.

wardivich
09-09-2008, 02:43 AM
thanks for that,

thats what i thought was happening.

8.4v batt - 3v Led - motor unkown.

i'm thinking that i'm gona have to get a bigger battery or a smaller motor.

wardivich
09-09-2008, 03:47 AM
i've got it working buy playing around with the resiters.

but i'm still wondering, if you have two componants from one power sorce, is there a way of securing a set amount of current to each componant? so it would work as if it was conected to two separate power suplys.

i don't need an explanation of how it would work, just the name of the thing (be it componant or circuit) that i can go away and reserch would be good.

SgtWookie
09-09-2008, 05:22 AM
i've got it working buy playing around with the resistors.
Congratulations :)

But I'm still wondering, if you have two components from one power source, is there a way of securing a set amount of current to each component, so it would work as if it was connected to two separate power supplies?
Yes, there are. You already know of one method; current limiting via resistors. However, this is not very efficient.

I don't need an explanation of how it would work, just the name of the thing (be it component or circuit) that I can go away and research would be good.
PWM (Pulse Width Modulation) circuits would be a great place to start. This is because instead of dissipating power (wasting it) by using resistors, you control how much current is given to a circuit by turning a switch on and off. The average power to the circuit is the same. PWM is a very exciting concept, and it is surprisingly easy to experiment with.

Check out our "Projects Collection" archives for various circuits.

wardivich
09-09-2008, 11:11 AM
excelent, thank you very much.
i shall start playing :)