Good evening folks!
I am looking to make a controller for a heat lamp that has a 200 V power supply. I wanted to use a Thermistor and a 200 V relay to control it. However, the Arduno is rated for 5 V, would this still work? Or will is there another way to circumvent this?
Thank you,
Tim
Yes, you can drive a relay with 5V. But, the Arduino can't supply enough current to power a relay coil so you need a driver circuit. You can get relay boards with a driver circuit built-in.
Or, there are solid state relays that can be driven directly by the Arduino. Just make sure the relay is rated for AC or DC depending on what you're switching because unlike regular electro-mechanical relays most solid state relays don't work with both. [u]These industrial-type[/u] solid state relays are super-easy to wire-up with screw terminals and they are easy to mount.
timtheb:
has a 200 V power supply.
...
a 200 V relay to control it.
Wouldn't you want a relay of higher voltage capacity for a bit of safety headroom?
DVDdoug:
But, the Arduino can't supply enough current to power a relay coil
Not from an i/o pin if that's what you mean, but you can certainly power a blue cube Songle style relay coil of just over 70mA from an Arduino 5V pin.
That would be one of these. Yes it has the circuity to which you allude, but can still be driven from Arduino 5V.
But switching large voltages one would probably want isolation, in which cas a board with the JD-Vcc style connections for a separate power supply, albeit another 5V one. But that's for isolation purposes, not because the Arduino can't provide enough current.
That would be one of these:
Willpatel_Kendmirez:
Not from an i/o pin if that's what you mean, but you can certainly power a blue cube Songle style relay coil of just over 70mA from an Arduino 5V pin.
As you may notice those relays require three wires: power, ground and signal. #1 was referring to powering through an output pin - the signal. Those relay modules in fact have a power driver built in.
wvmarle:
As you may notice those relays require three wires: power, ground and signal. #1 was referring to powering through an output pin - the signal. Those relay modules in fact have a power driver built in.
If "you" there means me, then yeah that's exactly why I posted that picture and said "it has the circuity to which you [DVDdoug] allude"
wvmarle:
#1 was referring to powering through an output pin - the signal.
Probably, but not umambiguously, hence my "Not from an i/o pin if that's what you [DVDdoug] mean". In the interests of not being ambiguous, he should have said he was talking about an i/o pin if he was, since it is actually not true to say the Arduino can't furnish enough current.
Thank you everyone for the help! Especially DVDdoug and Willpatel_Kendmirez. I will look into the relay link that was shared and see if it has the correct current range for my application. Futhermore, I will look more into the isolator board Willpatel has spoken about.
Sincerely,
Tim
Some brands of the board with proper isolation mark that other pin as "RY-Vcc" not "JD-Vcc", but whatever it's called, it's the way to go.
The other style, the upper photo in #2,even though they have an opto-isolater in there, and may be billed as isolatory, with the common ground it's not foolproof.
With the bottom one in the pics, the JD-Vcc style, it is true isolation as long as you wire it that way with the jumper off and separate supplies.