Hi!, So the project consists of two 5V pumps, two 5V relays and a 5V moisture sensor. I tried powering them using a 9V batter with converter but in some cases the two pumps won’t operate. Any advice to get through this?
Don't use 9V batteries. The only thing that they're good for is smoke detectors. If you need a battery, a much better choice is a cheap, rechargeable USB power bank. AC adapter is even better if you don't need the system to be portable.
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9V batteries shouldn't be used for devices with high current draw like pumps.
Is there an Arduino involved in this project?
Yes I’m using Arduino Nano
Thanks for the advice! So I can use any Ac adapter with a 5V output right?
No, not any 5V adapter. It needs to be rated for the max current your circuit will draw, plus at least 20% more for safety margin.
You can probably reduce the max current by using transistors/MOSFETs instead of relays.
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Ohhh but which transistors/MOSFETs you recommend me to use it ? Plus I am very thank full if you can explain to me how do the connections
Can I use the 2N7000 Sic MOSFET transistor?
No, I do not think they have enough current capacity for your pumps. They have a maximum current of only only 200mA. I do not know what current your pumps require, but I think it will be more than that.
I suggest IRLZ44, FQP30N06L or similar. They should be n-channel MOSFETs with logic-level gates.
Thanks for replying! And I just referred back to pumps specifications and found that it have a working current between 130 to 220 mA.
It's good that you know the detailed specs of the pumps.
But something else that may or may not be in the specifications is the stall current. This is the current that will flow for a moment when the pump starts, and also will flow if ever something jams up the pump and physically stops it from running. The stall current can be 5x or 10x the working current.
Your transistors should be rated above the stall current so that they do not blow when the pump starts up or stalls.
You should also remember to connect flyback diodes across the pump terminals so that the rest of the circuit is not damaged by the reverse currents/voltages created at the moment a pump is switched off. 1N400x (1N4001... 1N4007 etc) diodes will be good for this.
A 5V 2A adaptor is all you need.
Thank you all for helping me! I really appreciate that.
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