I have to switch a 230 Volt single AC-phase motor (0,18 kW / 2,8 Amp).
I tried to use a solid state relay, but (too late) I read that it can't function.
Now I intend to use a relay. On internet you see frequently a tiny PCB with a mini relay (specs 10 A at 250 V), see enclosed photo. I can connect it directly to my Arduino Nano.
Has anybody experience with this relay to switch an induction motor?
(the relay doesn't seem robust).
In stead of switching the motor via the tiny relay (option A in the drawing), I can use the tiny relay as an interface for a normal contactor (option B).
Has anybody a good tip?
I use a SSR to turn 230 volt AC on and off. You have been reading the wrong comics.
Post a link to the data sheet of that relay. The text on the relay is not readable.
ArduinoStarter1:
I tried to use a solid state relay, but (too late) I read that it can't function.
Where did you read this? It "can't function" because ......?
The most common approach is something like your B circuit, but using a transistor connected to the Nano instead of a small relay. A transistor is smaller, cheaper, draws less power from the Nano, and doesn't produce nasty inductive spikes. There are lots and lots of examples on this forum.
srturner:
Where did you read this? It "can't function" because ......?
The most common approach is something like your B circuit, but using a transistor connected to the Nano instead of a small relay. A transistor is smaller, cheaper, draws less power from the Nano, and doesn't produce nasty inductive spikes. There are lots and lots of examples on this forum.
S.
If the main relay coil runs from 230 volt a transistor will blow.
Having asserted that there are "lots and lots" of examples on this forum, naturally it took me awhile to find one...
So see answer #10 in this forum thread:
ArduinoStarter1:
I have to switch a 230 Volt single AC-phase motor (0,18 kW / 2,8 Amp).
It appears the relay in the photo is 10A rated for the output and may not be up to the job.
Reason being, motors such as induction motors on mains supply draw quite a lot of current during startup, 4 to 6 times full load.
You might get away with it in the short term but sooner or later the relay will cook itself.
BTW..."B"...never switch AC in the neutral conductor, big no-no.
ArduinoStarter1:
I have to switch a 230 Volt single AC-phase motor (0,18 kW / 2,8 Amp).
Those numbers are off.
2.8A @ 230V = 644W.
Should be a very easy job for an SSR, as long as they're designed for inductive loads (i.e. have a proper snubber or the TRIAC won't switch off). A simple TRIAC circuit can switch this just fine, too.
The problem with my first SSR is solved: I used a version of Fotek (type SSR-40 DA) to try switching an induction motor. Too late I read that the SSR operates with a zero cross trigger mode, so it is not suitable for inductive loads.
I looked for an SSR with snubber without zero cross detection, but could not find it.
I have my doubts about the reliability of the cheap tiny Arduino relay.
For my final solution I use a contactor (with 230 V coil) to switch the motor on and off.
As interface between the contactor and my Nano I use a SSR from Craydom (type MP240D4).
Interesting to hear the SSR doesn't work with motors. I have done speed control of AC motors of similar power as yours (~700W, 220-240V) using phase cutting. Works perfectly. Does require either a snubber, or a snubberless type TRIAC.
with phase control (fase-aansnijding), this uses an analog control voltage.
full wave control (volle golf) , this uses the zero cross trigger mode.
In the last case the integrated triac gets a short trigger pulse after the zero crossing.
The voltage on the motorwinding goes up, but the current needs to grow up; it wents too slowly.
The AC-current doesn't reach its latching current before the trigger signal ends. So this latest type is not suitable for switching inductive loads.
Bedankt voor het meedenken Wim
Thanx Wim for thinking along
A short pulse (10 us I think, have to check my code) is what I do when doing phase control... working well with standard TRIACs. The current obviously goes up quick enough in this scenario, even when switching very close to the start of the wave.
For a 100% duty cycle I switch at the zero crossing (when having such a detector built in - another project switching inductive loads does not so it just switches whenever) and simply keep the gate on until it has to switch off again.
