Electronics > Beginners
Voltage Drop at Breadboard
rdl:
I was not sure what more information another 6 inches of wire would add, after all, there is already ~425mm of conductor including 8 wire to board insertions, but I looked at it anyway.
I don't actually see much difference.
While I was at it, I measured the resistance of one 425mm length of breadboard rails (plus wire jumpers) at 18 ohms. If I did the math right, this agrees closely with the 40 mV voltage drop I recorded previously. The capacitance across the pair of rails (all 425mm) was measured as about 85 pF.
bd139:
A point to bear in mind when using or not using breadboards: Sometimes signal integrity and layout doesn't actually matter that much!
I'm doing some sub 1KHz stuff with opamps at the moment which requires a lot of trial and error. I'm doing it on a 3M breadboard and am giving zero fucks :)
rdl:
One more thing, and this is something that I've previously seen evidence of potentially being a real problem. This image is where the crosstalk is looked at on the long 425mm path. The blue trace is the actual signal on the "positive" rail (red jumpers), and the yellow is the induced signal on the "negative" (black jumpers) rail.
Here the same signal is running through one of the five hole vertical strips (blue trace) with the crosstalk that appears on the adjacent five hole socket strip (yellow trace). Doesn't look that bad actually.
I'd like to point out to anyone reading this thread that running a 10MHz signal through 425mm of conductor, including multiple wire to board insertion connections, is somewhere beyond "worst case scenario". I'm sure decent quality breadboards have a limit to their usefulness, but I don't know where it is and I'm not inclined to go looking today.
bd139:
On that basis you could have some fun and use the power rails as a directional coupler ;)
rdl:
Here are the waveforms with and without the extra 200mm jump wire inserted after going through the full 425mm rail length. I previously said I didn't see much difference. Taking a second look, the one with the extra jumper is actually shifted slightly more. While definitely something to keep in mind, it's not likely to be a problem in any circuit I would build on a breadboard. Signal connections there should always be as short and direct as possible, not two feet long with multiple jumper wire breaks.
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