Electric Valves

I'm working on a smart sprinkler system, and I plan to have electrically controlled valves as outputs - 4 of them to be exact. The particular valves I'm using require 12V to turn on (open), but the Arduino only supplies 5V by default. A solution I've seen is using a boost DC-DC converter to step up the 5V to 12V. However, I'm trying to save on parts; is there a way of not having to provide a converter for each valve? I.e. can I use a single component to step up any of the output signals since they are all being stepped up the same?

Do you think that you can use the Arduino to supply the power to the boost converter? You can't. You could have a 12V power source, powering the Arduino and the valves, using transistors that the Arduino triggers to actually operate the valves.

PaulS: Do you think that you can use the Arduino to supply the power to the boost converter? You can't. You could have a 12V power source, powering the Arduino and the valves, using transistors that the Arduino triggers to actually operate the valves.

I'm assuming having my Arduino run off of a computer or power outlet allows it to send signals to its outputs. Maybe I worded my original statement wrong. Is this assumption here also wrong?

[u]Here[/u] is a solenoid driver using a transistor (and separate power supply). Alternatively, you can use a MOSFET.

The power supply doesn't have to be separate. You can use the same 12V supply to run the Arduino as long as you don't run too much other stuff from the Arduino's 5V regulator.

DVDdoug: [u]Here[/u] is a solenoid driver using a transistor (and separate power supply). Alternatively, you can use a MOSFET.

The power supply doesn't have to be separate. You can use the same 12V supply to run the Arduino as long as you don't run too much other stuff from the Arduino's 5V regulator.

My question wasn't quite asking about if the Arduino power/valve power need be separate, rather does each valve need its own converter or can all valves use the same converter. Is there a way to universally make the Arduino's 5V output be 12V, and then control which are on and off from there?

does each valve need its own converter or can all valves use the same converter.

The same converter can power all the valves. But, where is the input to the boost converter coming from? NOT the Arduino.

Is there a way to universally make the Arduino's 5V output be 12V

No.

PaulS: The same converter can power all the valves. But, where is the input to the boost converter coming from? NOT the Arduino. No.

Thanks. Now that they have an (optional) 12V power source, where does the Arduino plug into with its different channels to control which valves receive power and which don't at any given time? You mentioned the transistor method above, but could you elaborate on that a bit

PaulS: The same converter can power all the valves. But, where is the input to the boost converter coming from? NOT the Arduino. No.

Also, if I'm using an external 12V source, is the converter even necessary now? My whole point for using the converter was because the Arduino supplies (yes, I get that it can't technically "supply" anything, but when powered it can transfer power) 5V max. My idea was when I want to open a valve, send HIGH (5V) from Arduino which is immediately converted to 12V which opens a valve, but using something external I don't quite get how to use the Arduino to control anymore

Think of it this way. The Arduino only supplies the signals for switching on the valves, not the power.

Assuming the valves are DC? The Arduino signals are logic level, 5 volts approx, and these signals are used to control the power switches to the valves. Then you need one 12 volt power supply to feed all the switches on one side (the positive).

Typically the power switches are transistors. So for example, the Arduino applies a signal to a transistor (base), and that transistor switches on the valve (negative terminal) via its collector.

If the valves are ac powered we need a different system.

yendis: Think of it this way. The Arduino only supplies the signals for switching on the valves, not the power.

Assuming the valves are DC? The Arduino signals are logic level, 5 volts approx, and these signals are used to control the power switches to the valves. Then you need one 12 volt power supply to feed all the switches on one side (the positive).

Typically the power switches are transistors. So for example, the Arduino applies a signal to a transistor (base), and that transistor switches on the valve (negative terminal) via its collector.

If the valves are ac powered we need a different system.

This makes a lot of sense. So, to be clear, I connect my Arduino to the base of a transistor, connect a constant 12V DC to the collector, and connect the valve's positive terminal to the emitter (and its negative terminal to ground). Then when I want to send the 12V through the transistor to the valve, I apply a HIGH (5V) from the Arduino to the base?

mhinkam:
Now that they have an (optional) 12V power source

There is nothing optional about it.

mhinkam:
You mentioned the transistor method above, but could you elaborate on that a bit

Have a look at the schematic that was linked in post #3

What is marked in the schematic as ‘ARDUINO_DIGITAL_OUT’ is connected to and output pin of the Arduino. You can replace ‘solenoid’ by valce for your purpose. For 4 valves you can use four IO pins of the Arduino.

mhinkam:
Also, if I’m using an external 12V source, is the converter even necessary now?

No

mhinkam:
My idea was when I want to open a valve, send HIGH (5V) from Arduino which is immediately converted to 12V which opens a valve, but using something external I don’t quite get how to use the Arduino to control anymore

You use it the same way; referring to the schematic, when you connect 5V to the base of the transistor via R1 (the part that is connected to the Arduino output) the transistor will be ‘open’ and current can flow through the valve (solenoid). If you connect the base to ground, the transistor is ‘closed’ and no current can flow through the valve.

Connecting to GND and 5V is done by the Arduino by setting a pin LOW or HIGH respectively.

mhinkam: This makes a lot of sense. So, to be clear, I connect my Arduino to the base of a transistor, connect a constant 12V DC to the collector, and connect the valve's positive terminal to the emitter (and its negative terminal to ground). Then when I want to send the 12V through the transistor to the valve, I apply a HIGH (5V) from the Arduino to the base?

No; again, have a look at the earlier linked schematic. 12V to one side of the valve, other side of the valve to collector of transistor; the transistor will provide the connection to ground (via the emitter) when it is 'open'.

sterretje: No; again, have a look at the earlier linked schematic. 12V to one side of the valve, other side of the valve to collector of transistor; the transistor will provide the connection to ground when it is 'open'.

According to the diagram, the solenoid is connected across the collector and constant 12V. But also, shown at the bottom is a SOLENOID POWER GND connected to ground. What I know is that the valve has 2 pins, a positive and negative. The only thing confusing to me about the schematic is where to connect the valve's negative pin -- to the collector, or to ground?

To the collector. The 'SOLENOID power GND' in the schematic is the ground (negative terminal) of the 12V power supply. The 'SOLENOID Power V+' is the positive terminal of the 12V power supply.

sterretje: To the collector. The 'SOLENOID power GND' in the schematic is the ground (negative terminal) of the 12V power supply. The 'SOLENOID Power V+' is the positive terminal of the 12V power supply.

Thanks. This isn't a great question, but what is the best way to provide 12V DC? Purchase of a variable DC source isn't optional, and this is also a school project meant to mirror a product for distribution, so adding something bulky like that wouldn't be ideal. Can a power outlet be used for this (if this should be obvious, please excuse my unfamiliarity)?

As is described by sterretje …
Electrical valves, if are motorized, strongly must be polarized as described on it (servos) . If you have a solenoid to simple open and close water ( directly, or non directly remoted - water pressure membrane) have no important polarity.

This is only the producer f…k, to serve it to people, who knows about it nothing.

Solenoid valves connection must be connected between +V and the collector in the case of NPN transistor is used or between collector and GND in case of you use PNP transistor.

If you use NPN, u must apply 5V HIGH voltage to base via resistor, in opposite case, is used 0V (LOW) to switch it On.

Is better to use a small (PCB) fuse for each solenoid, in the case of warm water flowing thru. Or in case of cyclic switching it.

Use a 12V DC power supply, with sufficient current capability to run at least as many valves as will be on at any one time. If you have picked a valve, please provide a link to the data sheet or product page.

BE SURE to add a "flyback diode" across each valve coil, to prevent voltage spikes from destroying the drive transistor.

jremington: Use a 12V DC power supply, with sufficient current capability to run at least as many valves as will be on at any one time. If you have picked a valve, please provide a link to the data sheet or product page.

BE SURE to add a "flyback diode" across each valve coil, to prevent voltage spikes from destroying the drive transistor.

This is what I was considering https://www.sparkfun.com/products/10456

jremington:
Use a 12V DC power supply, with sufficient current capability to run at least as many valves as will be on at any one time.

Does this seem to be something that could work? I will most likely have 4 or 5 valves total, with the possibility of all being on at once

mhinkam: This is what I was considering https://www.sparkfun.com/products/10456

Contact the manufacturer and ask how much current your specific model draws. Or buy one and a multimeter and measure the current ;)

mhinkam: Does this seem to be something that could work? I will most likely have 4 or 5 valves total, with the possibility of all being on at once https://www.sparkfun.com/products/9442?gclid=CPHRxMGpk8oCFQ8zaQodDZwH7Q

Wait till you know how much current is required.