Electronics > Beginners

Voltage Drop at Breadboard

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anbudroid:
Hello Everyone ..

      I Have a Chinese Bench power supply set its voltage to 7.5V send it Directly to DC-DC step Down Module Mounted in a breadboard. The output voltage of 5.07 from DC-DC Connected to Arduino nano and 1602 LCD. but after connection the voltage drop to 4.68. I remove the bread board and jumper cable and solder everything together then the voltage at arduiono 5V input is 5.04 . what cause this problem? I swap my old breadboard with new one but problem not solved .

       Am new to this forum. Searching internet for 3 days about voltage drop in breadboard and didn't find any result regarding this topic . so I thought this only happen to me. this is my second college project of my brother  I plan to help him in his electronic side. so I bought some breadboards , jumper cables and few op amps to play around little bit before we start . we both are not have much knowledge in electronics.

mycroft:
Many DC/DC converters requires a minimum load to satisfy the output voltage specification. See https://power.murata.com/datasheet?/data/power/ncl/kdc_cre1.pdf. The no load voltage can be much (>20%) higher.

tggzzz:
The problem is that you are using solderless breadboards. Inevitably you will spend more time debugging the breadboard than the circuit, due to variable and varying stray resistance, capacitance and inductance.

It is much easier to copy the masters, and use manhattan techniques or rat's nest techniques.

Ian.M:
Anyone working with Arduinos with female headers, or solderless breadboards etc. nneeds to be aware there's a lot of cheap and nasty flexible jumper cables with Dupont pin ends out there that are defective.

Common defects are: the stranded wire used is far too thin;  it isn't even copper wire; the ends aren't properly crimped; the wire has broken internally.    In all cases the resistance of the jumper will be excessive and if you draw a significant current through it you'll get a large voltage drop.   

Check the jumpers resistance before use after straightening it out and tugging gently on its ends to see if the crimps are loose or the wire's broken.  If it feels springy when you try to straighten it, or  stretchy when you tug the ends, breaks, or the resistance reads more than a fraction of an ohm over the reading you get with the test probes touching each other, discard that jumper. 

If you have more than one that are high resistance you can investigate further by stripping the wire and observing if its too thin, or if the wire is attracted to a magnet (copper coated steel), or fails the flame test (copper coated aluminum).

N.B the flame needs to be yellow as show, not a fully oxygenated blue blowtorch style flame as that can (just) reach the melting point of copper.

Doctorandus_P:
How much current is your LCD pulling out of the power supply?
4- line displays may go upto 100mA, maybe 200mA.
That would be:
U = I * R  =>
R = U / I =>
R = 200mV / 200mA = 1 Ohm.

This seems excessive.
The cheap Dupont wires from China often have a relaltively high resitance (usable for signal wires, but be carefull for power supplies)

Another possibility is your electronics boards drawing high current peaks, which result in short voltage dips, which get averaged by your DMM.
You can try distributing a few ceramic 100nF caps over the horizontal breadboard power distribution bar and add a fairly large buffer elco (100uF or so) to the right of the breadboard.

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