I am using a 9V 1A power supply for the arduino, powering via the barrel jack. In this moment I was thinking the same, maybe the 1A is not enough. iI try to find a 9V 2.1 A somewhere
do you have the specs of your 4 relay board ?
what's the current draw when you activate one relay's coil ? (this current will come from your Arduino 5V pin through the regulator which is already quite busy converting ~9V to 5V)
also can you clarify how you connected the pumps to the relay?
Is this your 9V power supply?
The 9V smoke alarm batteries have low current cabability. I suggest that you use a better power supply for your Arduino board.
Is the 5V supply well regulated? What are the specifications of the 5V supply? Why not power the Arduino with the 5V supply connected to the 5V and ground of the Arduino?
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Unfortunately It does not say how much current it is drawing. But I thought I would bypass that problem when using it in the JD Mode ? as the arduino should only provide the signal in that mode and the coil should be powered via the second power supply ?
@groundFungus No I have a normal power Supply you plug in your wall, on the bottom it says 9V 1A
the 5V is just a changeable power supply for the wall. I don't think it regulated well enouth to power the arduino via the Vin pin ??
ah I missed that part (small image not in focus)
you have to share the GND between the Arduino and the relay module though
Regulated or not, 5 volt is way under the spec for Vin. Connect it to +5 and make a test,
Good, that is OK then.
There are a lot of pages on the net that use the 9V batteries and a lot of folks have trouble with their projects when using those weak batteries.
I have not used those relay modules so am unfamiliar with their use. What is the purpose of the connection of 5V between the relay module and Arduino 5V?
Why not use logic level MOSFETs to control the pumps?
@J-M-L According to the schematics of the relay model not, as It uses the %v of the arduino and is Low Triggered.
@groundFungus I think the 5V is used to detect the Signal In as The relay Is triggered from Low Level Signals And needs to compare it to the 5V ?
I do not use MOSFETS as I don't even know what they are 
I am a mechanical engeneer and unfortunatly I know bare minimum of electronics 
So just connect the second Power Supply to the 5V pin ? Even If I do not know how well regulated those 5V are ? as I read that Those 5V must be from a good power supply?
Tried it, didn't help:(
I have merged your topics due to them having too much overlap on the same subject matter @fabi_pr.
In the future, please only create one topic for each distinct subject matter and be careful not to cause them to converge into parallel discussions.
The reason is that generating multiple threads on the same subject matter can waste the time of the people trying to help. Someone might spend a lot of time investigating and writing a detailed answer on one topic, without knowing that someone else already did the same in the other topic.
Thanks in advance for your cooperation.
You are right in being careful with an unknown power supply.
Have a look here >> What is MOSFET Transistor and How to use with Arduino? - Latest Open Tech From Seeed
Here is a MOSFET motor driver. I like the MOSFETs over relays because once the MOSFET is turned on the MOSFET will draw no current, unlike a relay coil that will draw current as long as it is powered. So a MOSFET is more efficient. Also a MOSFET can use PWM to control the motor speed. A relay cannot do PWM.
If you would like help on choosing a MOSFET, what are the specifications of the pump motor? Specifically, the rated voltage and stall current?
Thank you a lot. I have now tried to use the other power supply 9V-2.1A for the Arduino, but that did not solve the issue. Could It be that even that is to low or Is there any other possible Problem? I think The best solution for now would be to wait more time between samples , as there is no need to sample that often, The project would even work with just one Sample per day. And with a pause of just 1 min the sensor Values should have reset to the valid value. Would just be nice to find out why they behave like this, maybe to know it fore some future projects.
Do they all drop or does just one drop?
Do they jump around high and low or just stay low?
@jim-p they all go low
I’m not a hardware guy but that sounds fishy to me. Voltage doesn’t mean anything by itself. It’s 5V above some reference.
If your arduino reference (GND) is not the same as the relay module TTL reference how can this work reliably ?
There are 37 posts by now and no change.
From where do the relays current come? It should not be from the controller 5 volt pin but come from a power supply.
I wish You could sum things up, grab pen and paper and show the powering of the lot by a real schematics. 1 relay is enough to plot as the other ones are connected the same way.
TO SUM UP:
Every time I power something through the relay, the values of the sensors go down. The schematics are still the one from aboth, where the relay is powered from the second Power Supply and not from the arduino board it self. The 5V connection from the arduino board is just needed to detect when the Signals are set to LOW (comparing 5V to LOW from Signal input) . I am sure that it does not use the Arduino power to switch the relay, as it does not switch (make the clicking sound) if the second power supply is turned off. The 3 sensors are powered via the 5V pin of the Arduino. The arduino is powered from a 9V-1A power supply as shown before. But even switching that one for a 9V-2.1A power supply does not make a difference. I have tried another arduino board and another Relay module. The sensor values are only going down, if current is flowing through the relay. if it is switching nothing, the values stay the same.
For your sensor values to drop when the relay actuates, either
- the relay coil current is in the sensor return(-) path (drawing indicates not)
- the 5V of the Arduino ADC is sagging due to excess current draw (your evidence says no, as the coil voltage appears to come from the external supply)
- the sensor output itself is changing, unlikely but possible)
You sort it out - either your wiring is only approximately the same as the drawing presented, or you have a current path that is loading the Arduino regulator with the coil current, or something is hammering your sensors when the relay actuates.
I vote for the second one.