Resistor compatibility

Discussion in 'General Electronics Chat' started by bill502, Mar 20, 2008.

  1. bill502

    Thread Starter New Member

    Mar 20, 2008
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    Can a resistor that has 5% tolerance be used in place of one that was originally 10% tolerance if all the other values are the same as the original?
    The original was a 1/4 watt 2.2 ohm +/- 10% ( Red, Red, Gold, Silver). I ordered one from an electronics supplier, and when it came in, it was a 1/4 watt 2.2ohm +/- 5% (Red, Red, Gold, Gold). They told me it was actually better than my original because its tolerance would not allow it to fluctuate more than 5%, where my original allowed 10%. My thinking is that the resistor does not determine the amount of fluctuation in the voltage of the circuit, but must be able to tolerate whatever fluctuation may exist, up to +/- 10%. That being said, a resistor with +/- 5% tolerance would not replace my original because if the fluctuation exceeds 5%, it would possibly heat up and become a fuse at some point. Am I right or wrong? Thanks !!
     
  2. hgmjr

    Moderator

    Jan 28, 2005
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    I can't think of any reason that a resistor with a tighter tolerance could not be used in place of a resistor with a wider tolerance provided the resistance value is at or near the same value.

    hgmjr
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    Resistor tolerance refers to how close the actual value of the device is to the stated value. It has nothing to do with voltage tolerance. A resistor is insensitive to the voltage across it. The current through the resistor is critical. That determines the power it dissipates, by the formula P = I^2 * R (power equals the current squared times the resistance).

    A 100 ohm 10% resistor will measure anywhere between 90 and 110 ohms. The same resistor with 5% tolerance will measure from 95 to 105 ohms. That is a tighter resistive tolerance, meaning less variance from the stated value.

    At one time, 20% resistors were common. To get an accurate resistive value, you had to hand-select the resistor with an ohmmeter.
     
  4. bill502

    Thread Starter New Member

    Mar 20, 2008
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    Thanks for the explanation. To be sure I understand what you said, I can replace the original +/- 10% tolerance resistor with the +/- 5% with no trouble? Also, I confused voltage with current in my original question, but it made sense to me the way you explained it. I'm repairing an electronic speed control / radio receiver that is made on the same circuit board. I don't know what part of the circuit the resistor I'm replacing is on. Seems like there would most likely be current fluctuation on the speed control part of the circuit, so I just need to be sure the part I'm replacing will work. Thanks for your help, I do appreciate it !!
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
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    The 5% resistor will work perfectly well. Looking at it another way, modern parts are better made, so you can't even get 10% tolerance resistors anymore.
     
  6. bill502

    Thread Starter New Member

    Mar 20, 2008
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    I can't thank you enough beenthere. I appreciate your assistance as well hgmjr. I read in another part of this forum where a user was upset that a new user asked for help without having anything to offer to help improve this site. I must admit that my lack of knowledge about electronics classifies me as someone that has nothing to offer the site as well. I came here for help, and I found it. I'm very thankful that the site is available, and that there are people that will help others without expecting anything in return. Thanks again.
     
  7. beenthere

    Retired Moderator

    Apr 20, 2004
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    Thanks for your thoughts. The main purpose of AAC is to share knowledge.
     
  8. hgmjr

    Moderator

    Jan 28, 2005
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    Members neither new nor old are under any obligation to contribute to the forum. Many of our members such as yourself are still in the early stages of learning the basics of electronics. All members are encourage to participate at the level they feel most comfortable. If you never participate beyond asking questions that is just fine.

    Even new members often ask questions that illicit answers that can help illuminate a concept to another member. In this way even those who only ask for assistance can inadvertently help others acquire knowledge by the nature of the question asked.

    hgmjr
     
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