Using Mains Power

Hello all, I am in the middle of a semit complicated project and I am hung up on powering this project without eating up every outlet on the wall.

I am looking to power:
1 Arduino Uno
3 Peristaltic pumps

1 Heating element from a gutted coffee machine

I have attached a picture of the coffee heating element, I am hoping someone can assist me in figuring out what is necessary to power these from 2 or preferably 1 wall outlet.

Thank you!!

The pump is 12V, so you need a 12V power supply to start with.

I see a relay (the black cube thing), so you can use a relay to switch the heating element. A relay module can be bought. If you use a 12V relay, you can use the 12V we had to start with. Or you can use a SSR (solid state relay).

The Arduino Uno can be powered with 12V to the DC power jack or to Vin. But the voltage regulator might get hot. If that happens, use a dc/dc converter to make 7.5V out of the 12V.

In the photo, there is a round thing attached to the heating element. That is a bimetal temperature switch. If you use the Arduino to switch, you don't need that, but keep it for safety during development. The other orange-with-black-tip are temperature fuses. You must keep those, or else the element might melt or set things around it on fire.

interesting. huge photo, but out of focus.

the 4 diodes are in a bridge arrangement, so we might assume this board has DC. the clock/display board has 4 Tact switches, which further promotes that the board has DC.

if the clock has/is a micro, then there is a possibility you can replace that with an on/off signal.

the heater has two wires. the red one goes to a bi-metal switch. that is the entire temperature control circuit. too cold, the switch clicks for heat. too hot and it shuts off.

the large yellow block is most likely a cap to prevent a huge surge when the bi-metal control cycles.

if you want to get very hot water, just replace the timer with the arduino. nothing else needs to be done.

if you want to gut the thing, keep the bi-metal switch and put a temperature sensor on the coil and replace the existing relay with a SSR and then pulse the heat.

I always recommend opto's to isolate power and signals.

btw, you may be able to buy different value switches, so you could alter the temperature control.

as for temperature control, you are getting BTU's not temperature. faster water = lower temperature, but the BTU's will be the same as slower water and higher temperatures. as long as the heater is working. at least withing a window of efficient of the heater.

bottom line is that you will have a mains power unit. need only 1 power outlet, and can power both this and a voltage regulator or switching power supply for low voltage.

Ok so beginning with the pumps I was thinking something like this for the relay:

Thank you for your help on the coffee heating element, I don't mind keeping large portions of it I am after simplicity in making that work with the system. I am a bit confused on what you guys were suggesting on how to activate/deactivate this with my arduino wiring wise. Temperature and power management aren't necessary with this I just need to power it on and off.

Thanks for your help thus far, this has been an awesome learning experience for me!

That relay module can be used to switch the heating element and the pump. As dave-in-nj wrote, keep the bimetal switch, it will control the temperature for you.

Ok so I can use this relay for the 3 pumps and the heating element which is great! I just need to get a 12v power supply to feed the relay. How would I go about powering the arduino from this single connection to the mains as well? Are there any considerations I need to take into account when choosing a 12volt power supply to power this relay switch for the pumps and heating element and the arduino?

Use a regulated power supply of 12V. An unregulated power supply can have a voltage that is a lot higher.

Those pumps need about 300mA Three of them make 900mA.

The relays use about 50mA (I think, just a guess). Using a 1A power supply is too close to the limit, so I suggest to use a 1.5A or more power supply of 12V. For example a 12V switching power supply of 1.5 or 2A. The cheap ones cost between 3 and 10 dollars, and the good ones cost more.

Sounds great, Ill grab the relay and power supply and use something like this to power the arduino:

For powering the heating element, this may sound stupid, am I simply connecting the ground and live that was running to the outlet to the relay?

Please don’t use the name ‘ground’ for a dangerous mains wire.
The mains contains of the live wire and the neutral wire.

The output of the relay is not connected to anything else. Use the output of the relay just as if it was a switch in the mains wires.
So the mains wires connect to the heating element, and one of those wires is going through the relay output, in the same way as you would use a normal switch.

The buck converter for 12V to 9V is okay. Perhaps you don’t need it, and it is far more powerful than you need. But it is okay.