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| Voltage Drop at Breadboard |
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| tggzzz:
--- Quote from: rdl on March 20, 2019, 02:07:49 pm --- --- Quote from: tggzzz on March 20, 2019, 10:09:09 am ---I'm not entirely sure what you are showing there, since the detailed wiring matters. --- End quote --- --- End quote --- I don't see what the lower scope probe's shield is connected to. I expect the solderless breadboard has wide internal connections, in which case they will have a lower inductance than a wire of the same length. |
| rdl:
--- Quote from: tggzzz on March 20, 2019, 04:50:45 pm ---I don't see what the lower scope probe's shield is connected to. --- End quote --- It was connected to the same place on the resistor as the other probe and function generator when the screenshot was taken. I had disconnected it and was probing around at various places on the breadboard to see where and how much of the signal I could pick up. The induced signal was about 500 mV larger with the scope ground disconnected. |
| Jwillis:
I did an experiment to find the resistance of of a bread board compared a piece of wire and trace of a PCB.Its a simple test with a moderately priced mOhm meter , a typical inexpensive 170 mm breadboard with 145 mm rails , 145 mm of AWG 26 wire (typical breadboard wire I use) and 145 mm 1mm wide trace of 1oz PCB.This was done at or as close as possible to the same temperature of 20 C. And Zeroing calibration was done between each test. The results were not really surprising but interesting non the less .The bread board 145mm rail had a resistance of 46.5 mOhms .The 145mm 26AWG wire had a resistance of 40.2 mOhms . Trace 1mm on the 1 oz PCB showed a 120 mOhm resistance. All conductive surfaces will exhibit a resistance .And this resistance will increase with distance the narrower the path and increases in ambient temperature.This is unavoidable. If your expectations don't include this unavoidable variable then your project is beyond the realm of conventional conductors and into superconductors. Keep your paths as short as possible when prototyping your design regardless if you use a breadboard or PCB proto-board. |
| iMo:
FYI - the capacitance between the 5pin segments is 3.5pF. |
| tggzzz:
--- Quote from: Jwillis on March 21, 2019, 07:05:18 pm ---I did an experiment to find the resistance of of a bread board compared a piece of wire and trace of a PCB.Its a simple test with a moderately priced mOhm meter , a typical inexpensive 170 mm breadboard with 145 mm rails , 145 mm of AWG 26 wire (typical breadboard wire I use) and 145 mm 1mm wide trace of 1oz PCB.This was done at or as close as possible to the same temperature of 20 C. And Zeroing calibration was done between each test. The results were not really surprising but interesting non the less .The bread board 145mm rail had a resistance of 46.5 mOhms .The 145mm 26AWG wire had a resistance of 40.2 mOhms . Trace 1mm on the 1 oz PCB showed a 120 mOhm resistance. --- End quote --- And what was the variation in the resistance (a) with different (diameter, oxidation, dirt) wires (b) with different holes (c) when something was dropped nearby on the bench (d) tomorrow? Often the absolute value isn't too important, but stability and predictability is important. I would expect soldered joints to be significantly better in that respect. |
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