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Resistor and current calculation

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Indiann

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The voltage divider, divides the voltage but also reduces the current to zero.By making a voltage divider, i am getting an exact divided voltage(12 volt) with no current. It suppose to divide the voltage and not the current.

For example, if i want to divide 12 volt from 24 volt. I had used two equal resistor
(i.e)R1=10K and R2=10K
input volt vin= 24

Vout=Vin*R2 / (R1+R2)

How to divide the voltage without decreasing the current???
Advance thanks..
 

By dividing by half the value of each resistor, you keep the original current. Is there anything not mentioned in this question, or are you not very familiar with the Ohm's law ?
 

The voltage divider, divides the voltage but also reduces the current to zero.By making a voltage divider, i am getting an exact divided voltage(12 volt) with no current. It suppose to divide the voltage and not the current.

For example, if i want to divide 12 volt from 24 volt. I had used two equal resistor
(i.e)R1=10K and R2=10K
input volt vin= 24

Vout=Vin*R2 / (R1+R2)

It's no true "but also reduces the current to zero" , that equation is valid only when Iout=0

When Iout<>0 --> Vout=Vin*R2/(R1+R2) - Iout (R1//R2)


The voltage divider is not suitable for power source due the excessive dissipation and output highly dependent of the load.


How to divide the voltage without decreasing the current???

Forget voltage dividers unless for very low power applications. See "buck converters" or applications of MC34063.
 
Thank you eduardo, i understand now when to use voltage divider and buck converter. Can you show some examples or calculations of buck converter. I have searched but its not clear or understandable.
 

Thank you eduardo, i understand now when to use voltage divider and buck converter. Can you show some examples or calculations of buck converter. I have searched but its not clear or understandable.

Look for a MC34063 online calculator (ie **broken link removed** )

But in the datasheets you have circuits diagrams for many configurations and calculations.
 
Look for a MC34063 online calculator (ie **broken link removed** )

But in the datasheets you have circuits diagrams for many configurations and calculations.

Buck converter seem like complicated and i have tried the circuit not working.
 

Buck converter seem like complicated and i have tried the circuit not working.

Keep in mind https://www.aliexpress.com/store/pr...Voltage-Power-Module/1414081_32760917735.html


But you should have started with:
Input Voltage = 24Vcc
Output Voltage = 12Vcc
Output Current = ??? (The most important, who decides the type of converter)
Type of Load = ??? (for maximun ripple and voltage regulation)

According to this it will be preferable:
- Resistor divider or resistor series.
- 7812
- 7812+transistor boost
- Step down converter

Because the universal solution does not exist.
 

Input volt = 24
Output volt = 12
Input current = output current
Load = motor

According to this spec, it seems buck converter will suits. I thought of trying to make buck converter circuit rather than buying, so that i may get a little idea about voltage and current dividers.
Voltage divider used for divide voltage with zero current.
Buck converter (step down) used to reduce voltage, but output current will be as same input.

Can you guide me to make curcuit for buck converter.
 

Hi,

Input current = output current
According to this spec, it seems buck converter will suits
The first statment is true for linear regulators. But is is not true for (switching) buck converters (And if it really is the case with a buck converter, then the buck converter makes no sense)

Can you guide me to make curcuit for buck converter.
There are many buck converter ICs. (I´d never build one on my own. It takes too much time and i don´t think it is cheaper)
Many converter Ic manufactureres have interactive selection guides to choose the best fit.
The datasheet describes all to build a complete buck converter circuit. With all calculations, layout considerations and so on. Additinal information can be found in "application notes".
If you know a manufacturer of those ICs --> visit the internet pages

If you don´t know a manufacturer, then go to a electronic parts distributor´s internet pages. Then you will see some devices and the name of the manufacturers.

But as already said: You urgently need to know the expectable load current. Add some margin.

Klaus
 

Input volt = 24
Output volt = 12
Input current = output current
Load = motor

Do you think that the same circuit is used for a current of 100mA than for a current of 100A?


For a motor you not need any voltage converter, it's enough a simple pulse width regulator.

Something like this:

FIEG47SGXL5P0NJ-LARGE.gif

**broken link removed**

- It need a diode in parallel with the motor.
- Adjust duty cycle to 50%
 
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My input supply= 24v
Where my load (motor) needs only 12v. So i need to divide the supply voltage and i have to give load.
And i am also interested to know and willing to make buck ( step down) circuit.
 

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