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Resistor rule of thumb? — Parallax Forums

Resistor rule of thumb?

piguy101piguy101 Posts: 248
edited 2011-06-19 11:45 in General Discussion
I've read somewhere that the rule of thumb for resistors is to use half or less of the wattage it is rated for if you are using the resistor for extended duration. Is this true? I am planning on getting a 10W wire wound resistor and powering it around 8 watts, will the resistor be o.k.?

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2011-06-19 10:34
    A resistor rated at 10W is, unless the rating is specifically for a limited period of time, indeed designed to be used up to that amount of power dissipated. Some very high power resistors are specifically rated for a certain time on with a specific minimum time off to cool (like RF dummy loads).

    That said, your 10W resistor will run hot at 8W and the heat will affect components around it. You'll need some way to get rid of the excess heat like ventilation.
  • piguy101piguy101 Posts: 248
    edited 2011-06-19 10:37
    Would a small fan from a computer suffice?
  • Mike GreenMike Green Posts: 23,101
    edited 2011-06-19 11:45
    You could certainly use a small fan, but any setup where air can circulate freely would do the job. "Ventilation" doesn't always mean "add a fan".
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