using same power source for the Uno or Mega and a Nema 23

I should know the answer to this, but I am unsure.

If I run the Uno or Mega off of a 12v power source, and that same source is used to power a Nema 23 that the Uno is controlling using an easy-stepper or equivalent, am I placing my Uno in Jeopardy? I know I can't run the motor power through the uno, but if they originate from the same source, is that still a problem?

Logically I would think not, but logic and I are not always best of friends.

crchisholm:
I should know the answer to this, but I am unsure.

If I run the Uno or Mega off of a 12v power source, and that same source is used to power a Nema 23 that the Uno is controlling using an easy-stepper or equivalent, am I placing my Uno in Jeopardy? I know I can't run the motor power through the uno, but if they originate from the same source, is that still a problem?

Logically I would think not, but logic and I are not always best of friends.

That all depends on the voltage drop of the 12 volts source while the stepper motor is powered. If if stays pretty stable, then there is no problem. If it is not steady, then more capacitors may be needed in the power wiring so the pulses are reduced. There is nothing to hinder you from trying.

Paul

Keep in mind, an inductive load may affect electronics sharing that load.
i.e. you might experience some intermittent problems.

I see no issue as long as you don't series the ground or power.

If I were to do this I would run the power from the 12V source to the Arduinos, then run a different set of power lines to the Nema 23.

I would also add a 10µF cap in parallel with a 0.1µF cap at the Arduino. And maybe another pair at the Nema 23

I'm sure not all the added caps I've suggested are needed but the can't hurt.

John

“I see no issue as long as you don't series the ground or power.“

This confuses me a bit. I would think the arduino, the stepper driver, and the arduino would share a common ground. Something like this....

12v source —> driver motor voltage —> Arduino raw input (vin)
5v arduino —> driver logic input
GND —> driver —> arduino GND.
Caps where needed

Is that what your saying I should not do?

sorry...don’t have the ability to do a schematic right now.

By series the grounds I mean exactly what you described.

I would Run:

Motor <-------- 12Volt Source ----------> Arduino.
Motor <-------- ground -----------------> Arduino.

Motor input <--------------------------------Arduino.

My logic, the 12+ source has likely the lowest impedance, making it less likely the inevitable voltage spikes from the motor will reset of otherwise effect the Arduino.

The capacitors are for additional protection against voltage spikes etc. If you look thorough this forum can easily find a number of help requests where an Arduino is being reset when a relay engages or disengages a load. You may find it beneficial to have a small RC from the Arduino output to the Motor input (signal)

I think I understand your logic (maybe not). Perhaps you are thinking, if the Arduino is connected to the motor the Arduino will “ride” with the spikes and will not see them between the 12Raw and gnd. This sounds good at first but the spikes have high to very high frequency components that can go right to ground if any other circuitry is connected to the Arduino.

Also note, the effect is compounded by lead length. Shorter are better.

John

Ok, I think we're are on the same page. I plan to put a 50uf and a .1 uf next to the 12v power source.

Do you see any reason to put caps at other locations?

Im going to clean up my wiring a bit so that it more accurately reflects what you show above. At present I leap frog from the 12v src to the motor v input to the arduino vin. I will take everything back to the 12v source...same with grounding.

Hi Charlie,

I don't know if additional caps are needed or not. Its a Chicken Soup kind of thing (..couldn't hurt..)

Personally I usually and 0.01 to 0.1 µF at each circuit location and hold off on the electrolytics.

My logic: the small caps are easy to add.

One note from others, it seems like the type of issues that come up from relay noise etc are intermittent. The system could run fine for days then lockup or reboot.

Also ( it sounds like you already know this but..) when rewiring, keep the motor wires physically away from the Arduino and its wiring. Twisting also helps.

crchisholm:
Ok, I think we're are on the same page. I plan to put a 50uf and a .1 uf next to the 12v power source.

"Next to"?

The capacitors are there to provide impulse power to the device using the power. The power supply should already have a capacitor across its output. So you should have a 50 µF - or 100 or 220 µF - across the power input of each module except the Arduino which already has one at the input of its regulator.

Hi,

AsPaul mentioned the capacitors should be near the item / board consuming the power, I concur. I your case the Arduino and relay board.

The logic:

Noise spikes are generated at or near the relay board (due to the outputs switching some current). These voltage spikes get coupled into the wiring and travel to the Arduino through multiple paths. Adding a capacitor right at the relay board reduces the coupling and can be effective in squelching noise issues.
At the same time, the Arduino is susceptible to noise spikes and perturbations. Adding capacitors (very) near the Arduino will go a long way to stop any errant noise on the wires from reaching the Arduino's processor.

For noise reduction I would use a 0.01 to 0.1 µF capacitor in both places. These values (or this value range) is good for the frequencies generated by a relay contact and load.

Just a note, if the frequencies we were trying to suppress were in the 100's of megahertz range we would be better served by 100 to 470 pF capacitors.

The 100 to 500 µF suggested by Paul will definitely help "hold up" the V+ going into the relay board which helps if the power supply does not have much extra capacity but do not do a good job of suppressing the voltage spikes that could travel back to the Arduino. They do some but high frequency suppression is not their "thing" (so to speak).

John