Generally the fixed resistor is called a "stop resistor" It prevents (when) the pot is turned to zero ohms and a large current flows through the pot and it gets damaged.
A fixed resistor can also be placed above and below the pot so that when the pot is turned in one direction, the voltage at the top of the pot is passed to the centre pin and when it is tured anticlockwise, the voltage on the other end of the pot is passed to the circuit being controlled.
This allows the pot to have a maximum and minimum voltage and this voltage may control an oscillator circuit or a number of other circuits such as amplifiers, speed controls, etc.
A fixed resistor can be placed on the centre pin and in this case the voltage on the pot can be as high as rail voltage and providing the circuit requires very little current, it will see full rail voltage and the resistor will simply be a: "safety resistor"
This is just a starting-point as you can go into "pot resistances" and "resistor resistances" and fill a whole chapter. In fact this is a very important chapter that has never been presented in any text book.
I have seen a 1M pot used to adjust a resistance value for a 2N3055, where the resistance required is about 470R. I mentioned this to the owner of the site and here is his comment:
I often use the 1 MegOhm linear taper pots because they are precise enough for determining initial values. Once those are determined, you can take a resistance measurement and install fixed values in their place.
If you have ever tried to set a resistance of less than 1k on a 1M pot, you are better than me.
To advocate this on an electronics site shows how little you know and understand about electronics.
More of the above persons faults can be seen on Talking Electronics website
Spot The Mistake Page 12.
Selecting the right pot is quite a technical matter.
A fixed resistor can also be placed above and below the pot so that when the pot is turned in one direction, the voltage at the top of the pot is passed to the centre pin and when it is tured anticlockwise, the voltage on the other end of the pot is passed to the circuit being controlled.
This allows the pot to have a maximum and minimum voltage and this voltage may control an oscillator circuit or a number of other circuits such as amplifiers, speed controls, etc.
A fixed resistor can be placed on the centre pin and in this case the voltage on the pot can be as high as rail voltage and providing the circuit requires very little current, it will see full rail voltage and the resistor will simply be a: "safety resistor"
This is just a starting-point as you can go into "pot resistances" and "resistor resistances" and fill a whole chapter. In fact this is a very important chapter that has never been presented in any text book.
I have seen a 1M pot used to adjust a resistance value for a 2N3055, where the resistance required is about 470R. I mentioned this to the owner of the site and here is his comment:
I often use the 1 MegOhm linear taper pots because they are precise enough for determining initial values. Once those are determined, you can take a resistance measurement and install fixed values in their place.
If you have ever tried to set a resistance of less than 1k on a 1M pot, you are better than me.
To advocate this on an electronics site shows how little you know and understand about electronics.
More of the above persons faults can be seen on Talking Electronics website
Spot The Mistake Page 12.
Selecting the right pot is quite a technical matter.
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