I've recently taken over a project that a friend started, to measure and adjust several parameters for indoors hydroponics. The general idea is to have several sensors (ORP 1130 for pH/ DFR0300 for conductivity for example) which require 5V input voltage linked to an Arduino Mega and to VMA447 peristaltic pumps, there are 6 pumps in total
My friend used this 5V 18A power supply : Mean Well Power Supply 5V 18A 90W LRS-100-5 - ProtoSupplies and noticed that the voltage in the sensors (ORP 1130 for pH/ DFR0300 for conductivity) was not 5V as it should have been but rather between 6 and 6.5V. He suspected that was because the generator had too much input current and it increased the voltage.
This is quite a big issue because the voltage is not stable and it affects the pH measurement.
That's why he had the idea to use 5V voltage regulators to maintain it to the right value. I've been browsing for the right regulator when I realized that the VMA447 pumps require "6V/5W".
I read several topics about that before and know that you should always use the input voltage required and at least the input current. But I know that some devices tolerate a difference in voltage, so do you know if that's the case with these pumps and I can use a 5V input voltage? Or I need to change either the power supply or the pumps?
The Arduino board and the sensors might be damaged by the 6.5V. Stop what you are doing, and rebuild the project.
By adding 5V voltage regulators, you are trying to solve a problem by introducing another problem. If the power supply does not supply 5V, then you should get rid of it and buy a good power supply.
Can you show us a picture or drawing or photo that shows how everything is connected ?
Is the output of the power supply 5.0V ?
The power supply is connected to the mains, but where does the generator come from ?
I think that the VMA447 can run at 5V for a test. For the final version, you might have to use a 6V power supply.
The Arduino board has its own 12V power supply (on the right), and the 5V one I described is on the left. The 12V is only for the Arduino board and the 5V is for the rest. The Arduino does power an ESP8266 tho but I think that's ok.
I know the whole thing is a mess, it's probably better, and safer, indeed to just buy a new generator and rebuild the project
What is that generator ?
Is there no mains voltage ?
Can you show a photo of the growing plants, so I know that it is legal.
I power my boards with 7.5V to the barrel jack, or sometimes with 5V.
The Arduino Mega 2560 has onboard voltage regulator for 5V, if that has to power the relays and the ESP8266, then it might get too hot.
If you want me to check the sensor modules, can you give links to them ?
Here are the plants, they are not mine, I'm just an intern in the company but as far as I'm told, everything is 100% legal (I'm in France if that changes anything).
The generator on the right is 12V, 12.5A and powers the Arduino, while the one on the left is 5V, 18A and powers everything except the Arduino. So there is not one main voltage.
My main question was mainly if the 6V pumps could tolerate 5V and I got an answer to that but here the sensors :
From what I read on this forum, the PH modules can cause troubles. A PH circuit with galvanic isolation is better: https://www.tindie.com/products/rezahussain/dormant-labs-ph-module-v2/. Keep that in mind if your PH values are not stable.
Are those 12V relays or 5V relays ?
Just try the 6V pumps with 5V. It should work. But I'm worried about the voltages and wiring of the whole project. You could build something that will not work.
I prefer that you rebuild the circuit. Since relays are used, you could separate the two circuits, which is better for the PH sensor. However, using a single power supply has also advantages, and you can use DC/DC-converters to make other voltages.
If you boss asks you why you have to rebuild the circuit, then show this topic. I'm sure that others on this forum will agree with me.
With the "mains", I mean the power of the 230V sockets in the walls.
A "power supply" is a device to make a lower DC voltage.
A "generator" is a large device in a power plant that makes electricity. There are also small ones that run on fuel.
Groupe électrogène Loxam, place Émir Abd El-Kader, Lyon (mai 2019)
Sebleouf, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons
Thank you for your answer, my friend noticed that the pH and EC probes interfered with each other that's why he added voltage isolators (just above the sensors in the picture).
Those are " Keyes 5V 8 Channel Relay Module MD-011 250V AC 30V DC Funduino". It is used to control the activation of the pumps. Basically the sensors measure pH, EC etc, send it to the Arduino and the program checks if the values are in the range that we want, if not it triggers the pump
So your idea to rebuild the circuit would be one power supply connected to the relay, the relay connected to each sensor, the pumps and the Arduino (so a branch circuit? I'm not familiar with the English words) and DC/DC - converters in between if needed?
Can you make a schematic or drawing that shows how everything will be connected. A photo of a drawing on a piece of paper is okay.
The voltage isolators are very good. I assume that they are I2C bus isolators.
Did you know that the "Gravity" bus is wrong ? They put SDA next to SCL in a flat ribbon cable. You could split the wires of that flat ribbon cable and keep the wires as short as possible.
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