I have a cheap 24V, 15A power supply from China that I am using to power a TB6560 motor board with a 2.8A NEMA 23 stepper. I have my circuit designed such that the Arduino UNO is currently powered by my laptop via an A-B connection. What I am seeking to do next is power the Arduino using the 24v power supply unit. I’ve seen several posts on the form that discuss, to varying lengths, a similar problem to mine. However, what I can’t seem to find a figure out on my own is how to step the power down to 7V-12V for the barrel jack and also limit the input current such that it meets the suggested specs of the Arduino UNO. I am still very new to DC electronics. Insight and guidance is greatly appreciated.
Hi and welcome.
Stepper motors are controlled using pulses, and these pluses are quite likely to pollute the supply.
It'll be even more likely to do that if the price of the supply is related to it's build quality.
That's why you see lots of advice to use separate supplies for controller/motordriver and Arduino.
Current is drawn by a load, not forced into it.
Limiting an input current doesn't make much sense, as a device drawing too much current will already be dead.
Limiting an output current makes more sense.
It might look like nitpicking to say that, but consider this:
Limiting an output current might protect wiring to become a heating element, which might cause the isolation to melt and create yet another and larger short.
It will also protect your supply from damage.
Also, powering your Arduino through the barrel jack is easy but inefficient.
You'd be using your 24 volts supply to power a supply which powers the on board supply powering the Arduino.
Instead you can use a step down module (click !*), which will allow you to set an output voltage (meaning you have to adjust it before you connect it to your Arduino !) suitable for your Arduino.
It's set and forget, so once you set the output voltage, you won't need to readjust it for instance when the input voltage would change as long as it is within the modules' limits.
Connect the module output to a 5 volt pin of your Arduino, or 3 volt if it uses that (depends on the model).
Not to the VIN pin, that's the same thing as the barrel jack.
*The link leads you to a shop of a valued member of these forums, but has no ties to Arduino as far as i know of.
Of course you're free to go and see if you can find another source.
Thank you for providing great info and value.
Are you saying that I need an entirely separate power supply for a system of this sort to be efficient? I cannot simply use another terminal connection (there are 3) on the power supply I have? If so, how would this work then? 2 outlet connections, battery (truly not a viable option for me), or 2nd power supply?
My goal is to have the full unit turn on by connecting into a wall outlet. Most of what I have found online uses a laptop to power their Arduino which is not suitable for my needs. I plan to take this project of mine to pre-production in the near future.
No.
I'm merely explaining the most common advice, mentioning it in the 3rd line.
Each paragraph is meant to be an advice and/or explanation.
The module mentioned in the 4th paragraph would be powered from your 24 volts source, and creates the voltage your Arduino needs.
It does that with an efficiency of nearly 80 %, which is much better than what conventional regulators would do.
And if you'd do it the way i explained, you'd skip another regulator which is also an improvement of efficiency.
You might want to put some extra capacitors at strategic positions in your setup.
Mentioned module has some at the input as well as at the output.
You just need a DC-DC converter down to abuot 7.5V, and feed that into the barrel jack. The input to the DC-DC converter can be pretty horendously noisy with spikes and drop-outs and it will still basically work - the on-board 5V regulator on the Arduino can clean up and noise on the output of the DC-DC converter. In other words you have two levels of isolation from the motor supply, which ought to be enough.
Make sure any DC-DC converter has generous input voltage range. Something like a cheapo LM2596 module ought to suffice.