variable resistor in circuit


I am new to electronics forum  and would like some advice on building  the servo controller circuit  in image.

I understand how to construct  most of  the circuit  on the breadboard except for the wiring of the 100K variable resistor.

The 100K trim pot I am using has the usual three terminals but don’t know witch terminal to fit where .

If I understand it correctly the 56k resistor goes to the end of the pot  track the other  end to pin 7 pn the 555  

but I dont know  where the wiper terminal should go.

Any help welcome,





A variable resistor is nothing more than a voltage divider.  Knowing this, it stands to reason that one side must be positive, the other must be ground, and the whisker is your signal out.  so 56K is positive side of 100K variable resistor, whisker goes to pin 7, and the bottom side of 100K variable resistor goes to ground.

I don't think you can hurt anything trying this.

  Joined November 18, 2019      8
Monday at 02:06 AM

Hi Dale,in the circuit the 100K potentiometer is used as a variable resistor.So we have to connect  it's wiper pin to one of it's fixed end.Hence now we will have only two pins,connect one fixed end of 100K potentiometer to 56K resistor,and the other end which is also shorted with wiper end, will be connected to pin 7 of 555 timer.Hope it helps!!!

  Joined August 22, 2019      125
Thursday at 12:29 PM



Simply put, a variable resistor is able to have its electrical resistance adjusted. These devices are used when working with electrical circuitry because they help to control voltage and/or currents. They specifically work with voltage and currents that are a part of the circuit.

A variable resistor is the type of resistor which changes the flow of current in a controlled manner by offering a wide range of resistances. As the resistance increases in the variable resistor the current through the circuit decreases and vice versa. They can also be used to control the voltage across devices in a circuit too. Therefore, in applications where current control or voltage control is needed, 

  Joined November 07, 2019      124
Thursday at 04:25 PM