Power Supply and Pump Control using LM2576 and Arduino micro

Hello,

This is my first time here and I am new to the world of electronics. I have a personal project involving a vacuum pump that I would like to control via an Arduino while powering it through a lifePo battery.

I did some preliminary research, but it's all so overwhelming. To be concise, I figured the LM2576 would be a good fit for providing regulated power to a 12V vacuum pump, from a 14V lifePo battery pack. However, the LM2576 has pins for 'on/off functionality and "feedback".

So, my question is how do I use this in conjunction with an Arduino Micro to provide power to the pump, control the start and stop time of the pump, and record how long the pump has been in operation. I know the feedback on the LM2576 is supposed to do something, but it seems it would be unnecessary to use it when I have an Arduino MCU.

Please I need some guidance on how to better conceptualize and use both components effectively. Thank you.

Why not follow the drawing? Feedback controls the output voltage. That's a very fast process and it can't be done by any controller.

The drawing is for fixed output, without the use of the on/off switch, and the feedback is also not configured the way I am intending. I guess from your reply, I need to better articulate my question.

So my intent is to use the Arduino to control the functionalities of both the LM2576 and the pump. I intend to use the Arduino's I^2C to control the on/off actions of the LM2576 providing power to the pump. I also have a pressure sensor I plan to use to check the pump's pressure and subsequently control the on/off activities of the pump using I^2C and the feedback pin of the LM2576. In concise terms, it's to be all automated by the Arduino.
So my question is how to really reconfigure and redesign the schematics of the LM2576 so I can connect it to the Arduino, the pump, and the pressure sensor.

Here’s a link to the data sheet I had a look at. https://www.ti.com/lit/ds/symlink/lm2576.pdf

That circuit is a switching power converter providing a certain, adjustable, voltage and a few Amps.
There is no way, as I can see, that You can control that device by any other means than switching it On or Off.

What kind of control of the pump do You intend to use?

Hello,

There is a much easier way to reach your objective: use a solid state relay, a freewheeling diode and control the solid state relay using one of the 7 PWM outputs of your Arduino no electronics needed and your power circuit can be split from your Arduino circuit eliminating interference between the two.

Solid state relay persitaltic pump.

Best Regards,
Johi.

@ Railroader.

My intent is indeed to switch it on and off using an Arduino Micro's I^2C. My power source as I stated will be from a 14V lifePO battery. The LM2576 is meant to be strictly a power source for the 12V pump. However, I intend to also acquire data from the pump's activities using the Arduino. I have a control Pot for controlling the speed of the pump, as well as less for various indications such as pump run time and pump blockage.

As I stated earlier, I also have a pressure sensor for that actual pressure readings. I intend to use the pressure sensor to do the data acquisition and subsequently control the pump's activities. This is why I assumed if I connect the Vout of the pressure sensor to the Feedback pin of the LM2576 and the SCL pin of the Arduino, I can use the data from the sensor to subsequently control the on/off activities of the LM2576. The output of the LM2576 will just be connected to the Pump and nothing else.

Why a SSR? A simple N channel logic MOSFET could do, if the battery voltage is right.......

No, no, no. You can't use the feedback signal like that.
You can turn On or Off the regulator by using the ON/OFF pin, pin 5.

Keep things apart. One part is controlling the pump. Measuring this and that and out of that operate the pump comes as the next part.
Registering and book keeping are other parts that have nothing to do with the pump control.

What is the pump's rated CURRENT?

In other words, post a link to the pump....

Thank you for your inputs and help, sorry for not posting the pump first.
Here it is, it is rated for a max of 1.5A when powered by 12V.

Sorry I am new to this and it's not clear why the feedback cant be used to control the LM2576. Is it because of the passive/active nature of the pins?

I assumed since I was using a pressure sensor for data acquisition I could subsequently use that acquired date to turn the pump on/off using the LM2576. Unless another voltage regulator would be more suitable for the task?

I don't have a wiring schematic yet, but basically, I was going to connect the feedback pin 5 of the LM2576 to the SDA pin of the micro, the Vout pin of the pressure sensor, and an A2D in of the Micro.
The SCL would have been connected to just a resistor and the on/off pin of the LM2576, while the output pin would have been connected to the pump itself.

From your reply, it seems this would have been a recipe for disaster?

I don't know what to say without getting brutal.
The LM2576 is a switching power converter, likely using plenty of kHz switching frequency, pumping, pulsing the inductive element. The feedback line controls that pumping, pulsing.
Just drop the idea of manipulating the feedback. It would be the same as drilling holes down to the silicon chip and alter things.

Feedback is not at all a logic signal.

If You don't think my reply is good, please go ahead and make what ever wiring You want, blow things up. I will step aside and use my time on better things.

Thank you for your reply, it's been very helpful. Please don't get frustrated, I am trying to et a better understanding of these design choices. Upon reviewing the datasheet again (I didn't really understand all I read though), it seems the LM2576 is strictly a voltage regulator then. So why have the on/off pin if it's meant to be strictly connected to the ground (from their schematic) and not controlled by an external signal?

The on/off pin of pin must be connected to ground to have the converter running. That is correct.
It is possible to pull it high, letting it be Vin, the battery voltage. As the battery voltage is higher than controller Vcc additional components would be needed, a transistor, some resistors. That is all control Your Arduino can have on the converter.

Regard the power controller, the LM2576, as a power supply. All other controlling You add after the power supply, external to the LM2576.

Ok now I understand better, I was trying to cut corners and eat make my cake, and have it.

So I think my original question still applies. Once I decide to make the LM2576 strictly a power supply, how do I use my Arduino Micro to turn my pump on/off in light of these changes?
This is because now I see the design being multiple modules. For instance, once I connect the battery to the LM2576, power is immediately available to the pump. It is at this point I want to control when the pump turns on and off (despite it always having 12V power when the battery is connected?)

Also from this design change, all I will do with the pressure sensor is take the data read, and use it to monitor the activities. SO my other inquiry will be, how do I now get feedback to know when the LM2576 is either supplying power or not. More so, I will thus need to use this feedback to subsequently control the activities of the pump (such as speed and overdrive)

Okey. Fine.
You could draw a block diagram containing: pump power supply(ready), pump(ready)...

Yes, let the LM256 produce 12 volt like that. The pump only runs in one direction. Right?
Then a driver board can be used, or an N channel MOSFET + 2 resistors, to handle the pump, On Off or even speed controlled, by the Arduino Micro.

It's late here. I don't understand what "module" involve. You can tell later.

Pressure measurements , just for "knowing". No problem.

Now it gets nice and easy! As Your Arduino Micro is controlling the pump being On or Off, that information is clear. Log, print, register it...

I don't understand the criteria for the Arduino Micro to turn the pump On or Off.

You control 1 pin. When it is LOW, the regulator is supplying power.
When it is HIGH, the regulator is not.
0 & 3.3V or 5V from an Arduino will do.

Thanks again. For what is worth I don't really know what I meant by the module as well, I myself am getting tired.

Also, @CrossRoads (I hope you are not the same person with different user names, as this seems oddly coincidental) just provided insight from what I also saw in the data sheet.

I am exactly trying to put the voltage regulator into standby mode when it is not being used, but I don't know how to go about this using the prescribed TTL or CMOS? I know I am learning quite a lot, but there's only so much I can take in at a time.

As per the criteria for turning the Pump on and off, I just want to monitor for runtime, power draw (battery discharge specifically) and flow rate/blockage

@CrossRoads
You're perfectly right about the enable ON/OFF levels. My mistake. My mission was to stop messing ut the feedback input.....

ON /OFF CONTROL TEST CIRCUIT Figure 26 and Figure 32
VIH
ON /OFF Pin
Logic Input Level
VOUT = 0 V TJ = 25°C 2.2 1.4
Applies over full V
operating
temperature range
2.4
VIL
VOUT = Nominal Output
Voltage
TJ = 25°C 1.2 1
Applies over full V
operating
temperature range
0.8

@ cross roads

Thank you for your input. I am open to learning more, but I don't see anything on the datasheet that provides further information on how to implement this.

"You control 1 pin. When it is LOW, the regulator is supplying power.
When it is HIGH, the regulator is not.
0 & 3.3V or 5V from an Arduino will do."

From the above statement, do you mean I control just the on/off pin using the digital or Analog pins of the Arduino? Forgive my crude question as I am truly new to all of this at the same time.

So, basically, I can use one of the pins to implement a logic switch between high and low voltages for the On/Off pin?