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Topic: voltage divider help (Read 1 time) previous topic - next topic

mblackwolf

Oct 03, 2011, 03:54 pm Last Edit: Oct 03, 2011, 03:57 pm by mblackwolf Reason: 1
Hey guys,

I am going to be using a 6V battery for my project and need to step it down to other voltage for different components (i.e. 5V for arduino mega and my controller, 4.8V for servos, 3V for some other components). I am thinking of using a simple 2 resistor voltage divider since I dont know other ways minus a transformer. I know the basic equations (i.e Vout = (R2/R1+R2)Vin) but the thing I am stumped on is choosing the resistors. I know I can calculate the resistor values using the basic equations but I am not sure on if it will be better to use a combination of lower resistance resistors vs. higher resistance assume I can find a high reistance and low resistance pair that will do the same step down. Also, If I can find the right resistor pairs how do I choose the right wattage for the resistors as I have seen they typically come in 1/8, 1/4, 1/2, etc watt resistors. Thanks for any help also any suggestions on better ways to step down the voltage are greatly appreciated.

Just ran a quick calculation and wanted to throw in a example of the different resistor combos i.e. to step down 6V to 5V you could use R1=100 ohms R2=500 ohms or R1 = 1k R2 = 5k

Grumpy_Mike

Do not use a potential divider for generating voltages for powering stuff. It is the totally wrong thing to do. Use voltage regulators.

Noorman

You do not have to step down the voltage for the arduino to 5V there is a regulator on board.
The Arduino itself has a pin that can provide 50mA at a voltage of 3.3, so no need there as well.

Basically you do not need to step down a lot, check the specs for the servo, they tend to operate at a voltage of 6V.

Btw, using resistors for this purpose is not a good idea because of the power loss in the resistors.

Use voltage regulators instead, they are made for that purpose (78xx series).

Cheers, Peter
2B || !2B

... bonding electrons and bits!

mblackwolf

OK. Sorry I have a very limited electrical background do you typically build voltage regulator circuits or buy themm for specific voltages?

Grumpy_Mike

You normally buy them for a specific voltage. You only need to add two capacitors for a compleat circuit.

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