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How to make a resistive divider

A resistive divider is an electric circuit to which we join a voltage and so obtain its reduction. The resistive divider consists of two resistors, connected like in the following image scheme.

Joining a voltage to the point VCC, we obtain the voltage reduction at the point VCC/2. To calculate the voltage decrease at the point VCC/2, we apply this formula:

This way, we reduce the entrance power in function of the resistors’ values. Suppose we want to reduce the entrance power in half. For example, we have a 12 volt power at the VCC entrance and we wish to reduce it to 6 volts at VCC/2. We shall put that R1=10k and R2=10k. According to the formula:

According to the formula: VCC/2=6 volts.

This is a theory, but in practice, the tolerance in resistors’ values makes that we really don’t have exactly 6 volts, but 6,1 or 5,9 volts. If we need an exact adjustment of the exit power (VCC/2), we should exchange the R2 resistor with a 20k trimmer and ten circles. This way we vary the trimmer until we obtain exactly 6 volts at the exit VCC/2.

The wiring diagram of the resistive divider

The resistive dividers are used a lot in our assemblies with microcontrollers PIC, since their maximum admitted power is 5 volts. This way we can adjust the power entrance to the microcontroller we choose.

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