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Voltage Drop at Breadboard
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tggzzz:

--- Quote from: anbudroid on March 13, 2019, 04:11:43 am ---After reading all of the discussion and investing some times around the breadboard I finally convinced myself that breadboard are only worth to work with digital signals and non-precious analog circuits. if we want to test any project with confident, first thing is "say no to breadboard"

--- End quote ---

Digital waveforms are analogue signals, ones that are interpreted by the receiver as being digital signals. If the analogue waveforms don't meet the input specification, the receiver can misinterpret them.

The only digital waveforms you are likely to encounter are in photon-counting and femto-amp applications.

N.B. the frequency content of digital signals is determined only by the risetime; the  period is completely irrelevant. For a little theory and a practical demonstration, see https://entertaininghacks.wordpress.com/2018/05/08/digital-signal-integrity-and-bandwidth-signals-risetime-is-important-period-is-irrelevant/

Modern jellybean logic has frequency content above 1GHz. Work out the current required to change the voltage of a 5pF capacitor by 5V in 1ns (typical input/voltage/time). Now realise that a 2cm wire on a solderless breadboard has 20uH inductance. Finally work out the induced voltage v=Ldi/dt. And then you won't use solderless breadboards for digital signals :)

Read Bogotin's rules of thumb https://www.edn.com/collections/4435129/4/Bogatin-s-Rules-of-Thumb
Ian.M:
Digital logic on a breadboard is  not *THAT* bad - as long as you don't try to use faster logic than LS TTL and HC CMOS, and put the decoupling caps directly over or next to the chips, with their leads as short as possible into the holes closest to the Vcc and Gnd pins.

Clock inputs can be a problem, but the typical CMOS input protection diodes clamp overshot fairly well, and if you control slew rate with source termination you can usually eliminate glitches on the active edge that would otherwise cause double clocking.  Occasionally you may need to resort to source terminated twisted pair for a longer signal run, possibly with AC termination using a RC network at the receiving end to damp transients on the edges (100R + 22pF to 100pF).  Data inputs aren't usually a problem, as long as the clock rate is low enough for ringing to settle out before the next active clock edge.

It also helps if you are using a MCU with all the high speed stuff on one die, rather than a CPU with ROM, RAM and I/O spread over several breadboards.
tggzzz:

--- Quote from: Ian.M on March 13, 2019, 11:15:40 am ---Digital logic on a breadboard is  not *THAT* bad - as long as you don't try to use faster logic than LS TTL and HC CMOS, and put the decoupling caps directly over or next to the chips, with their leads as short as possible into the holes closest to the Vcc and Gnd pins.

--- End quote ---

I did specify modern jellybean logic, not mid-70s 40-year old families!

Lead inductance in DIL ICs could be a serious problem in the mid 80s.

Modern large devices are so susceptible they come with IBIS LCR specifications for each pin (including multiple Cs to different rails), plus the waveform for each different drive level.
anbudroid:

[/quote]

Digital waveforms are analogue signals, ones that are interpreted by the receiver as being digital signals. If the analogue waveforms don't meet the input specification, the receiver can misinterpret them.


[/quote]


 you are right sir , but beginners  are not play more than 10Mhz clock signals with breadboard. and most of the Arduino players are much below this level.
radiolistener:
I catch the same issue at breadboard which I bought on aliexpress. In my case, the root of cause was breadboard resistance. It leads to voltage drop down when circuit consumes a lot of current. In my case I was used high speed ADC with power consumption 300 mA. And voltage drop was about 0.3-0.6 V.
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