power supply


I have recently purchased an Arduino Uno and have been experimenting with it. I am trying to accomplish something as a personal home project. but, not sure how to go about powering the system.

I would like to control a 12V DC water pump and a 4500W 220V AC Heating element based on input temperature reading using an Arduino. When temp drops a preset value, I would like to switch on the pump and the heating element. I have an SSR to switch on the element. and a transister + diode to switch on the motor pump. I tried this individually. But, how can i combine this into a single project box in terms of power?

  1. Separate 12V power to Arduino and pump + direct 220V AC power to heating element?
  2. 220V into the project box and stepdown to 12V DC inside the box? if so, it will be great if you can direct me to a page that shows the setup where I can learn how to do this..
  3. All seperate inputs: 9V battery to power arduino, 220V AC from the wall to heater and 110V to 12V DC converter for motor.

any help is greatly appreciated. Thank you

That is 20A !
I hope you have at least a SSR-40DA. But even a (low quality) SSR-100DA is not very expensive:

How much current is the 12V water pump ? Which transistor are you using ?

You should be careful with the 220V. You can bring that into the box, but only when you are familiar with this.
You have to seperate the 220V from the rest in the box.

It is safer to keep the 220V outside the box. I recommend a second box with the 220V and the SSR. You still have to be careful how to do this, a loose 220V wire may not touch the wires from the Arduino.

It is possible to power the Arduino with 12V. The voltage regulator might get hot, but you have to test that yourself. If you can't keep your finger on the voltage regulator, it is too hot.

So use a power adapter of regulated 12V. Perhaps a switching power supply.
Use that for the DC pump and the Arduino.
If the voltage regulator on the Arduino board gets hot, use a DC-DC converter to lower it to 7V for the Arduino (or use a LM317).

Lets just talk about the 12 volt water pump first.
You can run it with a suitable transistor circuit, but a logic level mosfet may be a better choice. Make sure to include a protection diode.
If you are going to use the same 12 volts to power the arduino, put in some extra capacitors. As Erdin stated, 12 volts on Vin will probably work if there is not much load, but 7 volts there is the best. It sounds like you will not have much load.
Don't use batteries to power the arduino.

BTW: as Erdin said, it is best to put the SSR and 220 volts in a second box.

Thank you for your replies. It helped. The 12V DC water pump draws 1.05A. I tried the speed control circuit mentioned here with a TIP120 Arduino - motor de 12v con control de velocidad - Hazlo.... If MOSFET approach is better, could you forward me to a guide where I can learn how to approach it?

I will keep the SSR and 220V in a separate box as you suggested.

So, to summarize..

  1. Use 110V to 12V DC converter on the wall to the project box
  2. inside the box, split the voltage to (a) power motor outlet directly and (b) use a LM317 to bring down voltage to 7V to power the arduino
  3. 220V wall outlet to second project box with SSR and heatsink to power the heating element.

Hope I understood this right. I will try this week. Thank you again.

I see no problem with your current idea. Good luck, and let us know how it works out.

No, wait a moment.

The schematic at taringa.net is wrong.
The diode is a fly-back diode, and it should be next to the motor. Because it must protect agains a positive voltage spike.

Take a look at this: http://www.pighixxx.com/abc-arduino-basic-connections/
Click on "Set 2 (Card 4,5,6)", and look at "Card 5".
That is with a mosfet. You can also use the TIP122 or TIP120 with the 1k resistor as with taringa.net (only the diode is wrong at taringa.net).

The TIP120 or TIP122 is an old darlington transistor and it will get warmer than a modern mosfet. Perhaps your TIP122 needs a small heatsink, and a mosfet can do without. If you decide to use a mosfet, be sure that it is a 'logic level' n-channel mosfet.

The fly-back diode is over the motor in "Card 5".
There is also a capacitor of 1uF. That is optional, but 10nF ... 1uF could be used.

Why do you have both 110V and 220V ? Your house is on the border of Europe and the US ?

@ Erdin, in the US, we normally have 120 volts plugs etc., But there are two legs coming in to the house. 120, common, and another 120. Most of our appliances us 120 from one leg or the other, but some high power appliances such as stove/oven, hot water, and air conditioners, will tapp of both legs to take 240 volts.

I see, thank you. I didn't know that.

In Europe we don't have a wire with 180 degrees phase.
We do have "three-phase" plus the null wire (common wire). The three-phase is called "380V". Many houses have only one phase out of the three (plus a null wire), but for heavy duty machines there is three-phase power. The earth wire is dug into the ground at every house.

Imaging this: Some houses have more than one phase. For example the washing machine on a seperate phase. When the null wire gets loose, and the washing machine is on, the other phase with clocks and lamp and tv's will get 380V instead of 230V.

New to me. I learn something new ever day.

Hi, in Australia we have 3 phase, 415Vac between phases, neutral which is 240Vac between neutral and any phase.
Neutral connected to earth stake at each incoming power box.
So on a street hopefully adjacent houses are connected to different phase for their domestic 240Vac, that way the load on the phases is near equal.
Industry is the same, 3 phase in and stuff like lights setup to run on different phases to keep loads equal. Motors of course 3 phase.
Very few domestic installations use 3phase, usually single phase, however with reverse cycle air con and stuff like that some bigger houses are 3phase.
Some of the first multi-phase stuff way way way back used to be 2phase.
I can understand with 120Vac you have higher current for the some loads, so I can see why 120+120 on stoves and high load devices to help keep current losses down.