Current sensing and standard resistor

Click For Summary

Discussion Overview

The discussion revolves around the replacement of a broken resistor in a 12v switching transformer power supply, specifically addressing the suitability of using a current sensing resistor versus a standard resistor. Participants explore the specifications, color coding, and potential alternatives for the resistor, with a focus on resistance values and current handling capabilities.

Discussion Character

  • Technical explanation, Debate/contested, Experimental/applied

Main Points Raised

  • One participant describes a broken resistor in a power supply and questions the use of a current sensing resistor as a replacement.
  • Another participant expresses doubt about the original resistor's value being 0.01 ohms and suggests checking the color code using a calculator.
  • A subsequent reply reiterates doubts about the resistor value and questions the color code interpretation, suggesting it might be brown-black-silver instead.
  • Concerns are raised regarding the appropriateness of a very low resistance value (10 milliohms) for a soldered component, suggesting it would be impractical.
  • One participant confirms the color code as black-brown-silver and notes the difficulty in finding a 0.01 ohm 2 watt resistor, mentioning the possibility of using multiple 0.1 ohm resistors in parallel.
  • Details are provided about the power supply's specifications, including its voltage and current ratings, and its application in powering RC car equipment.

Areas of Agreement / Disagreement

Participants express differing views on the resistor's value and color code, with no consensus reached on the correct interpretation or the best replacement approach.

Contextual Notes

There are limitations regarding the assumptions about the resistor's color code and its specifications, as well as the implications of using a current sensing resistor versus a standard resistor.

I forgot ohms
Messages
7
Reaction score
0
I have a 12v switching transformer; one of the legs on a black brown silver gold 2w resistor is broken off. I have had zero luck finding a standard .01 2w resistor. I did find a current sensing resistor at the values, but should it be used. The resistor in the power supply is ceramic, I think, and bluish silver in color. Looks like the ones you would find in electronics store on the shelf but just not in .01.lol I took some EE in collage but only remember enough to be dangerous. Just wanted to be honest.
Thanks Brandon
 
Engineering news on Phys.org
Studiot said:
I doubt your resistor is 0.01 ohms.

Check again using this calculator

http://www.csgnetwork.com/resistcolcalc.html
That calculator doesn't have all the color bands for the multiplier. Here's a better image: http://www.google.com/imgres?imgurl...=X&ei=S7GHTdvGA4HerAHttuyzBg&ved=0CB4Q9QEwAA".

If it is a current sensing resistor, the resistance should be really small.

Are you sure the color code is black-brown-silver? Not not brown-black-silver (which would be 0.1 ohms, not 0.01 ohms).

If th current sensing resistor you have is the same resistance value as the one that broke, the only think that matters is how much current it needs to handle. A .01 ohm 2 W resistor can handle 14 A of current. Is your other resistor rating for that much?
 
Last edited by a moderator:
the resistance should be really small.

(Really) small yes, 10 milliohms, no. That is the sort of resistance of a soldered joint so would be a waste of time for any soldered in component.

If 10 milliohms was necessary in the circuit it would most likely be formed from a carefully sized pcb track.
 
It is black brown silver gold. I will check the specs on other resistor. My local distributor has access to five resistor manufacturer , and not a one offer. 01 ohm 2watt. Smallest I could find is .1 ohm 2watt. I guess I could parallel a bunch of .1 but don't have the space.
 
The power supply is a 12-15vdc 15amp. We use them to power battery chargers and tire truer. I race 1/12 scale RC cars. The tire lathe is to cut down foam tires to achieve proper roll out.
 

Similar threads

Current Sensing Resistors in an H Bridge Circuit
  • · Replies 1 ·
Replies
1
Views
10K
Current sensing/measuring circuit
  • · Replies 6 ·
Replies
6
Views
5K
How Can the Philosophies of Great Physicists Guide Us Beyond the Standard Model?
  • · Replies 6 ·
Replies
6
Views
4K