variable resistor in circuit

Dale Barton's picture


Joined: Nov 19, 2019

Replies: 0
variable resistor in circuit
November 19, 2019 - 10:22pm


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,





Jim's picture


Joined: Nov 18, 2019

Replies: 7
varialbe resistor
November 20, 2019 - 3:31am

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.

Debasis Parida's picture


Joined: Aug 22, 2019

Replies: 19
Variable resistor
November 20, 2019 - 10:31am

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!!!