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Topic: LM2596 for high and low power? (Read 337 times) previous topic - next topic

Combo

May 27, 2019, 12:01 am Last Edit: May 27, 2019, 12:05 am by Combo
I'd like to power an arduino nano with 5v and power some higher-current devices (e.g. motor) at higher voltages (e.g. 9v).  I'd like a single power source for the whole project, ideally a barrel jack.

I have this in mind: -

I'd like to use a barrel jack with the adaptor set at 9v.  These would be VCC1/GND and used to power the higher current and voltage motor at 9v.

I'd like to then take the 9v VCC1 and GND as an input to the LM2596, with the adjustor set to 5v output.  These 5v outputs, VCC/GND, would then power the rest of the circuit including the nano (via pin 27).

Is this approach viable? 

I'm concerned that current drawn from the motor upstream of the LM2596 will mess with the 5v output.

Any pointers would be much appreciated.

Thanks!




PerryBebbington


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I'd like a single power source for the whole
Perfectly  reasonable.

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Ideally a barrel jack.
A barrel jack isn't a power source, it's a connector.


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I'd like to then take the 9v VCC1 and GND as an input to the LM2596, with the adjuster set to 5v output.  These 5v outputs, VCC/GND, would then power the rest of the circuit including the nano (via pin 27).
No problem with that.


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Is this approach viable? 
Perfectly.


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I'm concerned that current drawn from the motor upstream of the LM2596 will mess with the 5v output.
The only thing you need to be concerned about is making sure that your 9V PSU can supply sufficient current for everything. If it can then you should be fine. Bear in mind that motors draw a lot of current (stall current) when they start or when the shaft can't move for some reason. Your 9V PSU must be able to meet this current requirement. If it can't, then the output voltage of the 9V PSU will drop, possibly to the point where the LM2596 can no longer supply the 5V you need. With this in mind, and considering that if a motor is stalled for a long time it can overheat (think about the mechanics of your project and if this concerns you) you might consider a (say) 12V PSU and two LM2596s, one for the motors set at 9V and one for everything else set at 5V. The 9V can then current limit without upsetting the 5V one (assuming the 12V PSU can supply enough current).

Are you using an LM2596 and building the converter yourself or are you using a ready made one? I suggest a ready made one, they don't cost much and they work.







Combo

Thanks that's very helpful.  The LM2596 I refer to are these complete modules: https://www.amazon.co.uk/LM2596-Converter-3-0-40V-1-5-35V-Supply/dp/B01GJ0SC2C/ .

The idea of using two of them is an interesting one.  I'm not sure I understand how a separate module for the motors could prevent the 5V circuit becoming underpowered if the motors pull too much current?

I'm using this power adaptor: https://www.amazon.co.uk/gp/product/B00WOIV8NE .  It can provide 2A and can be set at any voltage from 3v to 12v.

e.g. if I set it to 12v and the motor pulls 2A from its own 9v LM2596 module, will that leave the arduino circuit on the 5v LM2596 underpowered?

Apologies, no formal education in this area :)

PerryBebbington

First of all, don't be afraid to try stuff! As long as you don't connect things the wrong way around and as long as you don't apply voltages above the rated voltage for a device, you won't do any (much) harm. As long as you learn something when smoke comes out (smoke WILL come out!) then it's not a complete loss.

Try what you are proposing with the wall wart set to 9V and one of the converters set to 5V, see how you get on.


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e.g. if I set it to 12v and the motor pulls 2A from its own 9v LM2596 module, will that leave the arduino circuit on the 5v LM2596 underpowered?
Borderline. Converters swap voltage for current, so 2A at 9V won't result in 2A at 12V being drawn. There is, of course some loss in the converter, maybe 10 to 15%.

If the LM2596 supplying the 9V goes into current limit then it (probably) won't draw enough current from the 12V supply to interfere with the 5V supply.

If you are going to have a 2A load you should have a power supply capable of more, at least 3A, maybe 4A.

Start collecting old wall warts from electronic kit that's being thrown away, they come in handy, I have loads of them in my loft!





Combo

Cheers Perry you've been a massive help!

PerryBebbington


Paul__B

Start collecting old wall warts from electronic kit that's being thrown away, they come in handy, I have loads of them in my loft!
Hope the floorboards in there are adequate!

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