# Resistor between GND and + 5V in Arduino

I design a board based on ATMEGA328P (as in Arduino UNO). Now I am busy creating a power line. My controller will be installed on the electrical panel, so I need to provide a reliable, noise-resistant device.

Once in the examples, I saw a 180 ohms resistor that was installed between VCC and GND. What does this resistor give to the board? Should I use it?

I also assembled a chain of SMD capacitors (4 normal and 1 polar). Should I change the number of capacitors or their capacity?

• "Once in the examples, I saw a 180 ohms resistor that was installed between VCC and GND. What does this resistor give to the board? Should I use it?" Post a schematic of the circuit, not just the resistor - nobody can say what it's doing in your example if you don't show the example. – user133493 Nov 18 '18 at 6:19

That arrangement is correct, you use a bunch of ceramic .1 uf capacitors near the pins to decouple high frequencies and a big electrolytic one to help with low frequencies and keeping voltage stable in case of a mini power loss

i would make some additions to the input circuit though

simulate this circuit – Schematic created using CircuitLab

this would filter out high frequency noise coming from the power line as well as preventing your circuit from injecting noise to it, the 1 ohm resistor is there just to avoid any possible resonance and the inductor should be a very low q one or even better a ferrite bead like NFZ03SG501SN10D, these one are specifically designed for EMI filtering you will have to choose the correct one for your application

on the 180 ohm resistor, i am really not sure why is it present, my guess is that it guarantees some load on the supply so if a transient occurs the voltage stabilizes faster and to provide some noise immunity by lowering the load impedance

the obvious disadvantage is that you would be wasting power, if that's a concern i would suggest getting rid of it

now the most important part however to make the circuit noise resistant will be the layout, normally sticking to the following rules is enough:

1: keep the traces short and straight

2: unless you have some requirement don't make them extremely thin

3: use a ground plane, as uninterrupted as possible

4: keep decoupling capacitors near the pins and put a vias close to their ground pads

• Thanks for the detailed answer and tips on designing the board! I will use your power filter circuit. – Delta Nov 18 '18 at 6:59