Wednesday 17 June 2015

voltage - Using pot as variable resistor: should wiper be connected to spare end terminal?


I've heard somewhere that a rheostat uses two pins while a potentiometer uses three. But still, the thing i would like to know is if there's anything different with the adjustment if I wire the pots like this:


enter image description here


Or will it not matter how I wire it? Thanks!



Answer



Electrically, these 2 circuits are equivalent. However, the advantage of the circuit on the right is that if the internal moving tap loses contact with the resistive element, the circuit still appears as a resistance rather than an open circuit. The latter can cause problems with some applications (for example, causing a voltage regulator to lose regulation or generate a large voltage). That is why most designers use the circuit on the right.


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