Shopsmith Forums

DONJON Wireless Remote AC Switch

Short version:
Used a low cost Wireless Remote switch from Amazon to remotely turn my air compressor on and off. This thing cost only about $20 bucks, and now it's available for less. It's just a component, it has to be wired into a circuit. I wired it through the switch on a sound-deadening box for my compressor but it could easily be wired into a single outlet, or a remote switch extension cord could be made.

This device uses an electro-mechanical relay to switch power, not an electronic component, so it does not run hot or need a huge heat sink. The relay is rated at 40amps while the overall device is rated at 30amps. It does consume some small amount of current at all times that power is supplied to it, and I have to assume it consumes more to keep the relay closed when it switches power on, but all such devices will do that.

So far it works great. I can turn on the compressor anywhere inside the house. Haven't tried it much outside but it's supposed to have a 328 foot range and I'll have no need to get that far away. The device comes with minimal documentation, but is so simple there's not much to document.

Here is a link to the device on Amazon. Note that the vendor name changed from DONJON to VONVOFF in just the past 24 hours:
https://www.amazon.com/DONJON-Household ... 603&sr=8-2



The longer story:

I've been looking for a remote switch for my dust collector, a 2HP Reliant. There are a number of low cost AC remote switches available for around $20, but they are not rated for the current surge of a 2HP motor startup. The devices intended for dust collectors are more expensive, $80 to $100 and up. Some of the remote switches components are solid state switches which run very hot and require large heat sinks.

There's a video on YouTube where a guy used a DONJON Wireless Remote AC switch on a dust collector and he provided the link to Amazon:
https://www.youtube.com/watch?v=uB5boYLPFdU&t=477s

That looked interesting, but the dust collector is not quite ready for use right now, it's in the old basement and needs some duct work to run through the wall into the new workshop area. In addition I'm planning to have it vent outside as I mentioned in one of the dust collector threads. But I did want to get a remote switch on my air compressor also. This past summer I built a sound-deadening box for the compressor out of scrap materials, and that worked out great soundwise. But I still don't like leaving it on all the time, air will eventually leak and the compressor will go off, and now in the box there's a cooling fan running all the time it's on. So I got hold of one of these remote switches and wired it into the compressor box.

This device is very simple, it's a little plastic box with line and neutral input terminals, and switched line and neutral switched output terminals. For safety I tied the neutral wires together so that side of the circuit is never broken. The device uses a mechanical relay that you can hear clicking on and off. A little antenna comes out of the top and there's a LED and button the side for pairing remote controllers to the switch.

The first picture below shows the back panel on the compressor box. The metal box with the switch in the upper right, an antenna coming out of a hole in the top, and there's a hole on the side to access the Learn button to pair it with controllers. AC goes in, and then both switched and direct line voltage go to the 3-way light switch, and then the selected source line goes into that little switch/outlet combo that I used originally because I found it on the shelf. The extra outlet is sort of useful I guess, but it's only on when the compressor is. My wife made the labels but I can't crouch down to line them up so just pretend they look a little better than that. You can just see the fancy blue tape air filter mounting system over on the right.

The second picture shows the switch device in the metal box. The wiring doesn't have to be that complex, I used a pigtail between every connection in case something had to change.
FInal note: I thought I posted this thread yesterday but can't find it anywhere on the forum. Sorry if this is a duplicate.

I like both the idea and the price range. The Amazon ad includes pics with the covers off. The relay is motor rated but I don't understand why the HP ratings are so low in relation to amperage, 40 A and 1/2HP at 240 VAC. (But 1 HP at 120 VAC.)


Seems fine for a DC-3300, but it might have a short life expectancy on some systems.

- David

I was willing to test it out because of the low price. The HP rating should be based on the relay contact's ability to handle the high current during motor start up. If that motor normally draws 15 amps then in theory it could momentarily carry 100 amps through the contact spark. My compressor also claims to have a 2HP motor, but it's never blown a breaker on start-up the way the dust collector has. I'm about to order another one of these switches to eventually test on the dust collector, at $15.99 and free shipping it's not much of a risk. Maybe the contacts will burn up eventually. I could have the same problems just from using light switches instead of heavy duty switches.

Setting a couple of things straight.

Although the starting current of an induction motor IS several times the running current, that is not the reaon for the 'HP' switch rating. It is the turn off arcing that requires greater mass and material and spacing in the contacts.

Note the relay above. The 40A rating is for resistive loads(Not inductive and NOT capacitive). The 240v rating is less because the emf creating the arc is 'potentially'twice the 120v situation.

Yes typical wall mount light switches do not like inductive loads.

JPG wrote: ↑Thu Dec 03, 2020 6:18 pm Although the starting current of an induction motor IS several times the running current, that is not the reaon for the 'HP' switch rating. It is the turn off arcing that requires greater mass and material and spacing in the contacts.

This is very interesting, I wasn't finding much useful info about switches and HP rating. Can you tell me more about what is happening when the contacts open? I'm guessing the arc can get longer and maintain itself longer when the contacts open because there was current passing through them already instead of having to make that leap when going from open to close. Is there a lot of energy in the motor going back down the lines or something like that?

Yes typical wall mount light switches do not like inductive loads.

Quite by accident the switches will rarely be flipped with this remote in place. I've been through this before with a large fan though, common light switches can last a while but will eventually fail, and of course right when you need it to work the most. A heavy-duty switch lasted twice as long but still failed anyway. Not sure how 'heavy' it's 'duty' was supposed to be though.

It is not just the arcing with switching an inductive load, but also the large negative voltage transient produced (see link below for explanation) can damage your equipment (can be thousands of volts for a very short duration). This is why dust collectors typically use a magnetic starter switch like the one shown below. It is not cheap, but cheaper than having to replace your dust collector should it get damaged from using the wrong switch.

http://www.artisancontrols.com/UtilityI ... 0Loads.pdf

https://www.pennstateind.com/store/LR22 ... wgEALw_wcB