50A 240V Electric Brewery Wiring Issue: Can only fire one contactor at a time.

I am attempting to build an Arduino controlled brewing setup, using a Raspberry Pi to send serial commands to active a relay, which in turn fires the contactors for my 5400W electric heater elements.

ISSUE:

The problem exists when I command any subsequent relay, it activates, but the voltage is not passed to the contactor, and it does not fire. I have a 24V 2A power supply attached with both phases on the terminal bus.

I’m confident the issue is how I have the power distributed, and that the circuit when closed is the shortest path, and the current does not follow to the remaining contactors when activated following the initial contactors activation.

When firing off the any single relay, which closes the any one contactor, it works great. (Doing it via wifi :D)

GOAL:
I want to be able to command all my contactors to close individually, and simultaneously.

PICTURES ARE ATTACHED

What about a schematic ?

Here you go!

What sort of psu is it, some switchmode supplies do not like inductive loads.

Connect all the contacters together to see if it can power them.

It is a small, transformer. 2A, 24V. Wall outlet style.

Is it switchmode ?

24 v at 2A is 48W , thats a tall order for a transformer wall wart.

Measure its output voltage under load.

This is a 50 w transformer.

it weighs 1 KG.

If your psu weighs less its likely to be switchmode.

IronArtisan, we like to have more information. At this moment we know less than 5% of your project.
I would like to know how the Arduino, the Raspberry Pi and the relay module are powered. Do you have a complete schematic that shows that ? What is that shield on the Mega board ? Do you have a link to the relay module ? Perhaps you can give links to all the items you have ? What is the sketch ? Did you try a test sketch that turns on two relays of the relay module and check it with a multimeter ?

The problem exists when I command any subsequent relay, it activates, but the voltage is not passed to the contactor, and it does not fire. I have a 24V 2A power supply attached with both phases on the terminal bus.

You may need to employ a licensed electrician before you create a hazardous condition.

To repeat. You can fire any one contactor with no problem. It is only when you try to fire 2 or more contactors, only one activates. Is that correct? If so, your transformer does not have the current output capability for the contactors. The inductive coil of the mechanical contactor needs more power for the inrush of activation. Temporarily, find a few more transformers and wire one to each contactor, via your Arduino, etc. If it works, find a bigger, better transformer OR find contactors that have less current draw.

You have huge currents/voltages far too close to the RaspPi.

Rearrange the layout left to right like this:

RasPi -> control board -> relays -> contactors.

All wiring should be twisted pair between control board and relays and
between relays and contactors - every signal should be paired with a ground return
so the currents can cancel out - this greatly reduces EM interference.

Try and leave at least 6 inches between the high current mains and any other part
of the circuit, the contactors will put out massive interference as they operate.

If your relay board has the option for opto-isolation then use it.

Hi,

Hi, what is your electronics, programming, arduino, hardware experience?

Do you have a DMM?
If yes, then set it in AMPS mode and check how much current is used to in the coil of the contactor to turn it ON.
Also measure the RESISTANCE of the contactor coil.

Lets work out the load before suggesting power supplies.
Spec/part number of the contactors too please.
What voltage are you switching with the relay board to the contactor coils?
Those coils look like they are 240Vac coils from the label between A1 and A2.

Also a proper circuit diagram will help, including AC in, your DC power supply and how they are all connected.

Tom..... :slight_smile: