LEDs lowering my voltage

Question

I'm getting to electronics and I have ran into a big issue. When I connect LEDS to my breadboard in parallel my voltage drops. I read in the past about series decreasing voltage and parallel decreasing current. So I got myself a power supply with a bunch of amps. But when I connect LEDS my voltage decreases.

As I add more LEDs my voltage continues to drop, with just 4 LEDs my voltage dropped from about 4.97v to 4.90v D: (the loose wires is where I measure the voltage)

The voltage matters alot to me because I have components that are designed to run at 5V but I want to have other stuff on the breadboard too. I seen other people who do this though, they have many components and stuff on their "5v rail" and it all works good.

Ive been trying to figure this out but I haven't had any luck.

Im really confused. Can anyone help? D: thanks.

edit for response, powersupply is 12V 2A connected to a breadboard powersupply set to 5v mode.

Answer 1

What you are seeing is the voltage drop due to resistance in the breadboard and jumper wires. As current increases (by adding additional parallel branches of LEDs), the I²R losses increase.

If you rebuild your circuit off-breadboard and use better conductors (for example, a perf- or protoboard with shorter distances and thicker wire) you should see less voltage drop.

You should also measure the voltage close to the supply and determine if the supply is failing to maintain the proper output voltage, or if it really is just on account of losses in the wiring.

That said, 70 mV is not going to be a problem for most 5V components such as a microcontroller or other IC.

Answer 2

The nominal voltage for whatever components you are referring to may be 5V, but there is definitely a tolerance. They won't stop working at 4.99V nor will they be destroyed at 5.01V. More likely they are specified to work from 4.5 to 5.5 or even from 2 to 6V.

It's natural for voltage to drop when current increases because of series resistance. If you had an 8.5 digit voltmeter you'd see a lot of digits changing. On an analog meter the needle is hardly moving in your example. If you are drawing 80mA total with 4 LEDs (I can't see the resistor values clearly) and the voltage changes 7mV that represents a resistance of about 0.09 ohm, which is pretty low- not an unreasonable order of magnitude for the breadboard itself even if the regulator was perfect.

I suggest you make measurements along the length of the breadboard bus strips to get a better feel for the numerical values involved. Use wires that do not have current flowing through them - just connections to the meter.