| Electronics > Beginners |
| Resistance of resistor leads ? |
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| magic:
It's best to measure that kind of things when they aren't rated by the manufacturer. I've built a tiny, TL431-based, USB powered 100mA current source for such measurements. Test current goes through the DUT and develops 0.1mV of voltage on it per each 1mΩ of resistance. Works on wires, cables, switches, connectors, anything. The basic idea can be found in TI TL431 datasheet. I've modified it a bit to avoid error from base current, another possibility is to simply replace the BJT with a MOSFET. |
| ArthurDent:
Perf board or breadboard, why worry just about the leads and ignore what could be a bigger problem. --- Quote ---"Breadboard is commonly rated for five volts at one amp or fifteen volts at one-third of an amp, both of which have a power dissipation of five watts. Since these specifications vary depending on manufacturer and the type of breadboard, you should check the data sheet before purchasing your breadboard. Due to the temporary nature of the contacts, most breadboard has a current limit of one amp or less." --- End quote --- https://electronics.stackexchange.com/questions/223702/what-is-the-current-carrying-capacity-of-a-single-stripboard-track |
| tooki:
Did you paste the wrong link possibly? The page you linked to does not contain the quote, it's about perfboard, not solderless breadboards. Moreover, that quoted text makes no sense... yes, 5Vx1A=5W and 15Vx0.3A≈5W, but the breadboard isn't dissipating that! Or rather... if your breadboard has 5 ohms of resistance in a contact strip, there's something massively wrong with it!!!! I tested a few of my breadboards, some eBay, some 3M/ASP, and other than one really bad eBay one, they all have around 9-10mOhm resistance. Also, I've checked, and I can't find any breadboards with actual stated current/voltage specs. The data sheets do not specify. |
| ArthurDent:
--- Quote --- "Did you paste the wrong link possibly? The page you linked to does not contain the quote, it's about perfboard, not solderless breadboards." --- End quote --- The quote refered to solderless breadboards, like the one pictured above, and the link refered to perf board, like the one pictured in the link. Sorry if that wasn't clear. I understood it. --- Quote --- "I can't find any breadboards with actual stated current/voltage specs." --- End quote --- As to solderless breadboards having current ratings, check the link below where one well known supplier rates this board of theirs at 1.5A. The info is out there if you search for it. https://globalspecialties.com/media/k2/attachments/EXP-350E_datasheet.pdf The point of my previous post was that only paying attention to the wire size was ignoring a very important aspect of testing a circuit either on perf board or breadboard. Within the safe current rating of either type of board I avoid using wire that is too small and could cause contact problems in breadboards. Note that breadboards may also have frequency ratings that can cause other problems. I stand behind what I posted. |
| tooki:
Well, “the data” isn’t out there for most breadboard. I stated that I hadn’t seen any that specify it, and that was true. Believe me, for the 3M ones, I’ve looked. It’s not out there. (And I’m not even going to try looking for cheap Chinese ones, since their specs would be unreliable anyway.) A few others I looked at didn’t mention it, either. That one vendor does specify it doesn’t mean that all the rest do. Ok, so what is the source of the breadboard quote with the nonsensical dissipation thing? As for breadboards’ limitations: please, please let’s not start on this again. It’s not necessary for every thread where the word “breadboard” appears to devolve into a holy war about their merits and limitations. The OP wanted to know about wire ampacity and that’s been explained quite well. |
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