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Thread: 240v Power Relay Board
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4th January 2021, 09:49 PM #1Woodworking mechanic
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240v Power Relay Board
Does anyone know if there is an Australian equivalent to this relay power board?IoT Power Relay - COM-14236 - SparkFun Electronics
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4th January 2021 09:49 PM # ADSGoogle Adsense Advertisement
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5th January 2021, 12:05 AM #2.
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I've looked for in 240V varieties but have yet to find one.
If you are hoping to use them for long term induction motor control, it's most likely the relays are not suited to this.
Relay switching of motors been discussed in the MW forums.
Most relays might be able to handle the high start up currents these motors use but the high voltage pulses generated during motor switch off will eventually burn out the relay contacts.
The rated 400,00 switching operations will almost certainly be for non-inductive operations (I have one of these relays working on a tempering oven and another switching a heater on my Dipersed Oil Particle Generator and they works great.)
However, such relays will have buried in the fine print of their spec sheets ratings of only a few hundred switchings for smaller inductive motor switching operations and maybe even less for larger motors. My experience is they generally do last a bit longer than this but not a whoo lot more.
There are a few ways /alternatives for inductive motor switching including;
- accepting the low ratings and be prepared to replace the relay. I have a similar relay on my TS and have replaced it ($6 on fleabay) on average about every 2-3 years.
- modifying the relay with a protective circuit to reduce the effects of the high transient resulting from switching off.
- use the relay to switch a generic motor contactor.
- use 3P motors on VFDs and control the motor through the VFD at low V.
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5th January 2021, 10:31 AM #3Woodworking mechanic
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It’s for a trim router
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5th January 2021, 11:42 AM #4.
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So about 700W and a universal motor?
Not sure about Universal motors - but probably better than an induction motor.
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5th January 2021, 11:53 AM #5Woodworking mechanic
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Yes. Makita 710W brushed.
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5th January 2021, 08:12 PM #6
Reading the fine print in the documents section of the web page in your link, the unit can be controlled with a low voltage, low current signal, signal high relay closed, signal low relay open.
If you feel capable of mounting some goodies in a plastic box, you could do the same sort of thing for a single circuit with the box, a 3 pin socket, a cable gland, a bit of acrylic sheet and a solid state relay. The solid state relay uses 3-20Vdc to control a 240VAC circuit, input signal high for closed circuit, input signal low for open circuit. There is substantial isolation between the AC and DC ends of the unit, but the acrylic sheet can be used to partition the box into 2 sections for AC and DC by cutting to divide the box into two, then cutting a close fitting opening to straddle the solid state relay. Relay is basically a blob of epoxy with 2 screw terminals for the DC control signal and 2 screw terminals for the AC circuit. Here is a Jaycar link for the device I am thinking about, they mention a heatsink but that should not be needed for 2.5A nominal for the router. There are much cheaper units on ebay etc, just make sure that the control voltage and controlled voltage ratings are similar to the one in my link, as they come with a range of ratings.I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.
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5th January 2021, 08:36 PM #7GOLD MEMBER
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It's not quite the same thing, but easily set up to do something similar - Itead make a range of IoT switches, including the Sonof 4CHPro (although it sounds like you only want to control one device? In which case the Basic will do.)
They're dirt-cheap, and very hackable - you can upgrade the onboard flash memory (need decent soldering skillz), and there are several custom firmware options available on GitHub (I use tasmota and node red).
I've got several of the gen2 devices around the place, some with original firmware, and some hacked. I note that the R3 linked to above says it supports a DIY mode, so it may be simpler to adjust to your needs. Otherwise just get the R2 version and google away - it's a very popular device in the automation/IoT hacking community.
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6th January 2021, 11:37 AM #8
My response was based on using basic logic level signals to control the device, e.g. Mach 3/4 CNC controller outputs a high state to run the router motor and a low state to switch it off.
Bernmc's solution is all WiFi based rather than logic based, so you would need something connected to a network to generate the WiFi signals for the modules to respond to. This is the major difference between his response and mine.
I'm not sure what you want to have remote control of the router for, or what you want to provide the control signal from, but the dc controlled solid state switch seems to more closely resemble the device you originally enquired about and would be suitable for using the trim router as a spindle in a CNC router with a software controlled motor function.I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.
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6th January 2021, 02:10 PM #9Woodworking mechanic
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Malb.
I’m after a unit that will be switched by an arduino or CNC controller so your solution is spot on.
Bernmc’s solution is fantastic for another project I have in mind .
Thanks to both of you for your input.
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6th January 2021, 03:56 PM #10.
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Even though it has 5V logic outputs an arduino won't be able to direct drive Malbs suggested relay. To do this with an arduino it will need a secondary relay with attached logic level circuitry.
I've successfully used something like this.
5V Single Channel Relay for Arduino | eBay
Screen Shot 2021-01-06 at 12.30.23 pm.jpg
I've even used a few of these on Arduino projects to switch 240V directly (not on induction motors).
This one drives the 240V 80W heater in my DOP machine.
DOPelectrical.jpg
The adapter shown in the pic above only provides the 12V power for the Arduino.
The mains that travels through the relay comes from a separate connection.
If you want to incorporate RF remote operation this is also cheap and easy using the $5 Sonoff RF fob and $2 RF Antenna attached to the Arduino. as I show in this mockup.
RF remote VFD control
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6th January 2021, 08:57 PM #11Woodworking mechanic
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Thanks Bob. I’m well aware of the need for a relay with the Arduino. I’m also playing with RF as well
FA11A846-2380-4139-83DC-2C62E6FB9696.jpg
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