Powering a submersible waterpump from same power source

Hi!
I’m building a compact self watering system consisting of a moist sensor, a water pump and an arduino (see attachment). I’m trying to power the submersible 5V water pump and the arduino from the same 5V source (common 5V micro USB charger >1A). However with my current setup, whenever the relay is triggered to start the pump the pump doesnt run and instead what happens is that the (what I think is the voltage regulator, right under where the Arduino Nano V3.0 text is) of the arduino get hot. Can someone explain what is happening and also provide a suitable solution?

Everything else seems to be working fine and also this setup works when I have completely separate power sources (That is a separate charger for the pump)

type of parts I’m using:
Submersible waterpump 3-6V
Relay Opto 5V

Image from Original Post so we don't have to download it. See this Simple Image Guide

...R

My guess is that you need a much more substantial power supply for your pump. The motor in the pump may draw a lot more than 1 amp for a very brief period at startup.

A simple test of this is to power the whole system from a pack of 4 x AA NiMh rechargeable batteries (4.8v). They can provide a lot of current for a short period.

By the way your diagram looks very nice but I would have no confidence that I can interpret it correctly, Consequently I am not going to comment on the overheating issue.

A simple pencil drawing showing all the connections with clear labels will be much easier to understand - even if you are poor at drawing.

...R

Robin2:
A simple pencil drawing showing all the connections with clear labels will be much easier to understand - even if you are poor at drawing.

...R

would a schematic drawing be better? Just to avoid having to draw by hand :slight_smile:

juaspo:
would a schematic drawing be better? Just to avoid having to draw by hand :slight_smile:

If it is as clear as a pencil drawing, yes.

I had assumed that (like me) you would find it easier to draw a schematic with pencil.

...R

yea the schematic design in fritzing had some flaws with some components so I resorted to hand drawing.
Think I have all the necessary details.

That drawing is very much easier to follow.

You appear to be powering the moisture sensor from Arduino I/O pins. Can you be certain that it will never draw more than about 20mA even if the sensor pins are short-circuited? A current limiting resistor might be a good idea.

Now you need to try a power supply that can deliver more current.

...R

Robin2:
You appear to be powering the moisture sensor from Arduino I/O pins. Can you be certain that it will never draw more than about 20mA even if the sensor pins are short-circuited? A current limiting resistor might be a good idea.

Well I did some measurement before to see just how much current was required and as I remeber it was below 20mA so (thinking 15mA or so) so it shouldnt be an issue and I did the test dipping the leads into a water.

Robin2:
Now you need to try a power supply that can deliver more current.

I guess so, although I does feel a bit counter intuitive to have a more powerful power source when the arduino gets hot as is already. It is as if it get shorted somehow and just gets increasingly warm until I remove the power. I havnt tried to see how far it goes before something happens but I suspect that something would be the magic smoke.

juaspo:
I guess so, although I does feel a bit counter intuitive to have a more powerful power source when the arduino gets hot as is already.

Having a power supply that provides more current at 5v will not exacerbate the heating problem unless there is already a faulty circuit with a short.

If the present power supply is inadequate the Arduino may get into a frenzied state of re-booting over and over again every time the motor tries to draw power and the voltage drops.

It would be worth trying the program without the motor connected to the relay - just put an LED with a suitable resistor in place of the motor so you can see that the logic is working.

...R

Why do you have power and ground for the moisture sensor connected to digital pins?

Normally the output of a moisture sensor is connected to an analog input. Post a link to your sensor.

jremington:
Why do you have power and ground for the moisture sensor connected to digital pins?

Normally the output of a moisture sensor is connected to an analog input. Post a link to your sensor.

Thats because I want to be able to turn on and off the sensor since keeping it on in a moist soil will cause electrolysis to happen which will ruin the sensor.

I know I could connect one pin to GND or 5V and the other to an output pin but this was a much simpler connection on the experiment board I had since it didnt require any additional wiring. This sensor comes with an additional circuit that delivers a digital output depending on a threshold value set with a potentiometer so no need to connect to analog input and interpret the input yourself.

type of sensor

I tried with a better power source and lo and behold it seemed to work however the overheating of the arduino issue is still there and I had to shut it down since it got so hot I couldnt keep my finger on it. So the questions now are is there an easy way to reduce the power consumption of the pump enough for the charger to work. I'm thinking maybe a cap in between and the second question is why does the arduino over heat and how to stop it from doing so. I made a similar circuit with another arduino unit and got the same result with it over heating so this is not just a unit thing.

5v volts into Vin will not work on a 5v Arduino.

Motor should have a kickback diode across the coil.

Forget the relay, use a logic MOSFET to control the pump.

juaspo:
I tried with a better power source and lo and behold it seemed to work however the overheating of the arduino issue is still there and I had to shut it down since it got so hot I couldnt keep my finger on it.

You need to identify what is causing the Arduino to overheat. Disconnect all the external devices and run the program. If it does not overheat then, add back one device and test again. etc etc.

I had missed the fact that your 5v was connected to the Vin pin in your diagram. The 5v power should go to the Arduino's 5v pin.

So the questions now are is there an easy way to reduce the power consumption of the pump enough for the charger to work.

I don't know where the charger comes into the picture, but NO, you can't reduce the power consumption of the pump. The power it draws is what it needs to be able to do the work. Moving a liquid is hard work.

...R

larryd:
5v volts into Vin will not work on a 5v Arduino.

yea I see your point I forgot about the voltage regulator voltage drop so the arduino won't receive the full 5V so thats a good point

larryd:
Motor should have a kickback diode across the coil.

Yes I've read about this and will add it but as I understand the kickback is for when the motor stops to prevent voltage spikes into the arduino but since I had a problem getting it to run I figured that couldnt be it.

larryd:
Forget the relay, use a logic MOSFET to control the pump.

Could you elaborate on why? to me it seems the pump wouldnt mind whichever is used so I assume it has something to do with the arduino?

Robin2:
You need to identify what is causing the Arduino to overheat. Disconnect all the external devices and run the program. If it does not overheat then, add back one device and test again. etc etc.

I assume it has something to do with the pump or the relay since it doesnt get hot if the pump is not connected

I dont think I was clear enough but when I tried the whole circuit without the pump everything works as it should and the relay is triggered as should. This also goes with when I have a separate power source for the pump. So the problem I faced was overheating and pump not running when I have both the arduino and the motor connected with the same power source as shown in the pictures. Since I dont want to have separate power sources for this I want to figure out what the problem is and try and solve it.

Robin2:
I don't know where the charger comes into the picture, but NO, you can't reduce the power consumption of the pump. The power it draws is what it needs to be able to do the work. Moving a liquid is hard work.

By charger I meant a common cell phone charger of 5V 1-2A

juaspo:
I dont think I was clear enough but when I tried the whole circuit without the pump everything works as it should and the relay is triggered as should. This also goes with when I have a separate power source for the pump. So the problem I faced was overheating and pump not running when I have both the arduino and the motor connected with the same power source as shown in the pictures.

You did not say in Reply #14 whether you changed the 5v feed into the Arduino from Vin to the 5v pin.

If everything really is connected as in your diagram then I can't see how the pump being connected could cause the Arduino to overheat. In your diagram none of the current for the pump flows through the Arduino.

It would be a good idea to have a kickback diode across the pump terminals to prevent the motor from feeding voltage spikes into the system but I would be surprised if its absence is causing the overheating.

...R

ah no I still havnt tried connecting from Vin to 5V so I still have to do that and I will return with the results I get. But yes that is why I'm asking in this forum since I cant see why this is happening either. :-\

juaspo:
ah no I still havnt tried connecting from Vin to 5V

Be very careful here.

I did NOT say that you should connect the Vin pin to the 5v pin.

I said that the 5v power supply should be connected to the 5v pin and not to the Vin pin.

...R

And if you connect the external 5v supply to the Arduino 5v pin, ‘do not’ plug the Arduino into your computer USB port.

Update on the situation.
Moving the pin from Vin to 5V did the trick so now everything works as it should. I don't know why but when 5V was connected to the Vin the temp on the regulator started ramping but when applied to the 5V everything seems to work just fine so thanks all for your help