12varduinovoltage-regulator
I am quite new to electronic and I'd like to build a setup plugged with a 12V PS (because there is a water pump in my setup).
But at the same time, I'd like to feed the Arduino VIN with the same power supply. Is it a good practice to use a regulator to go from 12V to 5V for a H24 setup? I mean, will it burn because of too much power dissipation?
If no, how can I supply the Arduino VIN in a more elegant way?
Do you have the DC supplies and Arduino grounds connected together? If not then any PWM from the Arduino will not work.
Most small plug type DC supplies are floating, so their grounds will not be connected to USB ground (of course the USB ground may be floating if e.g. on laptop battery)
As Russell mentioned a diagram of your connections would be useful.
Thanks for the diagrams:
Your problem is as stated above, you need to connect the grounds together. Otherwise, the Arduino PWM signal has no return path (remember a voltage is always relative to something) to Arduino ground since the grounds are not connected.
It's okay to connect all the grounds together (arduino and DC supplies)
The only time is isn't is in the very rare case where you might have a supply "ground" that is above earth ground relative to supply grounds (e.g. a 20 V supply with V+ at 50V and V- at 30V relative to earth/AC ground could not be connected to a 20V supply with V+ at 20V and V- at 0V)
If in doubt you can test for any voltage between the grounds with a multimeter (e.g. one probe to one ground, one to the other ground) but since most DC supplies are floating (not referenced to earth ground) then essentially the outputs are just like batteries.
Hope I haven't confused things here :-) Connect them together and let us know how it goes. Here's an altered version of your diagram (note extra black ground lines):
The first choice to make is whether you want to switch the input to the 12 V power supply, or switch the 12 V to the pump. If the pump spends a lot of time off, then powering down everything is probably a good idea. The 12 V supply will take some idle current, which is a waste if the 12 V isn't used for long periods of time. On the other hand, if the pump is on a lot and is turned on and off a lot, it will be easier to switch the 12 V to the pump. You could then even run the microcontroller off of the 12V, perhaps even with a linear regulator if you can keep its current down.
To switch the line power into the power supply, a plain old relay would be the simplest choice. There are plenty of relays that can be controlled from 5V that are intended to switch line power. Your supply will take well under 1 A, so there will be a wide choice of relays.
To switch the 12 V power to the pump, I'd probably use a transistor as a low side switch. Since the 12 V is already isolated from the line, you can tie the - side of the 12 V supply to the processor ground and use a direct connection. Lots of stuff can switch 1 A at 12 V. Here is a simple circuit:
Best Answer
The Arduino MEGA, Due, Pro, Pro Mini and UNO are all capable of handling an input voltage of 12V. The limits are even higher. If you're using a different one, check the product specification
Cheers.