Questions about Electrical Noise

Thread Starter


Joined Mar 23, 2019
Newbie question... I've learned how to program microcontrollers and create basic circuits. Now I want to put this together into a real-world project. One thing I have not learned about is "noise." My design has one cabinet with 60 amps of AC controlling 7 kW heaters, 24 volt motors, and various other equipment. The second cabinet, located adjacent to the first, has all of the electronics with sensor inputs and other circuits. The question is this: Should I anticipate or try to mitigate any "electrical noise" from the high voltage side affecting the low voltage side?

I'm trying to get this as close to right on the first try and would like to know if there are any topics I should study before finalizing the design. Any help or direction would be appreciated!



Joined Jun 19, 2017
Yes, you must always anticipate and mitigate "electrical noise".

An electrical schematic showing all of the Loads ( 7KW Heater, 24v Motor and various other loads with Voltage & Amps )
and the exact components used to control those loads
and all of the of connections to the microcontroller
and all of the Power Sources ( AC Voltages, DC Voltages, Amps, etc )
and all Grounding Points
would be helpful.

Motors & Inductive loads can cause much more noise than resistive loads.


Joined Mar 10, 2018
A general mistake among embedded designs is to terminate inputs
with relatively hi z sources which in turn leads them to be sensitive
to coupling. The driving force for that is minimize power. That's a
tradeoff one has to constantly look at in high noise environments.

Capacitor technologies for bypassing always of concern. Example
of ESR performance of bulk caps -

Ground bounce due to high current load flowing thru common ground
with UP, especially when joint ground node remote from source, eg.
distribution inductance, a problem.

Sensor cabling, shielded, many times necessary.

Look at todays high current products, like take the lid off a MIG/TIG
machine, look at what was done. Same for floor robots.

And of course general magnetic and e static shielding.

Regards, Dana.
An isolated power supply provides noise immunity by eliminating ground loops and transient voltages caused by other devices on the same power bus. The isolated power supply also protects sensitive components and humans from dangerous high voltages. The flyback converter is a simple design that contains few components and provides galvanic isolation between the input and output.

Thread Starter


Joined Mar 23, 2019
Thank you everyone for the replies. Sorry for the delay in responding.

Mvas: Yes, a schematic would be helpful. I am working toward creating one. I have schematics for some of the components, but nothing that shows everything together yet. I do have a list of the inputs and outputs, which I will upload. It will take me some time to get the schematic together.

I think one of my biggest concerns is using USB to send data back and forth to the PC. I keep thinking RS485 or CAN, but USB is native to the microcontroller and PC, which makes it attractive.

Are there any topics I should google to study?




Joined Jul 18, 2013
There is a paper on a similar issue relating to equi-potential bonding in electrical enclosures by Siemens, I am not sure if it is still out there but I do have a copy if needed.
Although seldom seen on PC's now, RS232 was the original standard and was/is used in the industrial CNC world for transfer of programs from server to shop floor CNC machine.
Personally my last choice would be USB for data transfer in that kind of environment.
One thing stressed in the Siemens paper is proper earth grounding,


Joined Jul 18, 2013
I have also seen laptops used on CNC RS232 that have lost their COM port.
Often due to the machine having its own source of 1ph 120/230vac and the laptop plugged into a nearby factory receptacle.
I always ensured the Laptop used a 120v outlet that was generally supplied on the actual machine for this purpose.