Thread: Remote control on DC-7 dust extractor.

The issue is not as drastic for you as it may initially seem. In it's simplest form, you want a sealed box with small low voltage transformer, a low current fuse, maybe a rectifier, and an adequate heavy duty mains rated relay or solid state relay mounted inside. The transformer and rectifier supply a low voltage supply that feeds into the remote switching circuit and ultimately activates/deactivates the relay to switch the dusty on and off. The box with this gear is hard wired between the mag switch and the motor, so the mag switch stays active unless you switch it off or the mains power fails, so you keep the blackout protection it offers but have the advantage of the distributed low voltage control system to operate the motor as required.

There should be extremely low additional risk of fire with such a system, because you can isolate the control system and motor by turning off either the wall outlet or the mag switch when you won't need the dusty, i.e. away from the shed, and you are using a fused low voltage/low current control system. If you wanted to up the ante a bit, you could replace the lv control system with a commercially sourced wireless remote system and pendant transmitter similar to garage door remotes.

I would not use a supermarket/hardware store mains remote unit for this application as they are rated 10A max current and that is around the operating current for your system. These motors have high start up currents and I have known the relay contacts in the supermarket/hardware store units to end up to be either burnt out or welded in the on position if expected to repeatedly handle large start up currents or stop large motors.

If you can access a sparky willing to work with you on the project, it would be worthwhile from a piece of mind aspect if you are unsure about things.

It can be even simpler than that. The switch on the motor has five wires, live, neutral, earth and two for the speed sensing switch to hold the switch on while the DE is running. Pull the switch off the motor, blank off the hole, run a length of five core cabtyre* from the motor back to where you want the switch inside the workshop and mount the switch in a 2x4 electrical box on the wall, next to your light switch. All you’ve done is extend the motors own switch and all the failsafes remain in circuit.

* check with your electrician if cabtyre is legal in this application. It may well be that you require a shielded cable such as Surfex or an armoured cable.

Originally Posted by Colin62

It can be even simpler than that. The switch on the motor has five wires, live, neutral, earth and two for the speed sensing switch to hold the switch on while the DE is running. Pull the switch off the motor, blank off the hole, run a length of five core cabtyre* from the motor back to where you want the switch inside the workshop and mount the switch in a 2x4 electrical box on the wall, next to your light switch. All you’ve done is extend the motors own switch and all the failsafes remain in circuit.

Theres no need for a 5 wire cable.
The switches used on Aussie DCs are the "no volt" or "electromagnetically latching switches" with the latching often built into the switch so teh switch is a simple 2 wires in and 2 wires out with earth wires connected separately.

The simplest way is to
- Open up the existing switch on the DC and note what coloured wires go where (VERY IMPOTANT)
- Remove the existing switch and power cable to the DC switch and relocate these inside the shed inside a suitably insulated box and preferably alongside a power switch.
- Then insert a suitably rated (1.5mm^2 cross section) cable in between the relocated switch and switch box on the DC making sure.
- the connections MUST be like for like and make sure the earth wire goes right through to the motor by testing for continuity with a multimeter.

To do this properly a suitably rated box and proper cable glands are required.
I do realise this is beyond the expertise and comfort zone many DIYers so I don't encourage this sort of this on these forums.

Originally Posted by BobL

Theres no need for a 5 wire cable.
The switches used on Aussie DCs are the "no volt" or "electromagnetically latching switches" with the latching often built into the switch so teh switch is a simple 2 wires in and 2 wires out with earth wires connected separately.

The simplest way is to
- Open up the existing switch on the DC and note what coloured wires go where (VERY IMPOTANT)
- Remove the existing switch and power cable to the DC switch and relocate these inside the shed inside a suitably insulated box and preferably alongside a power switch.
- Then insert a suitably rated (1.5mm^2 cross section) cable in between the relocated switch and switch box on the DC making sure.
- the connections MUST be like for like and make sure the earth wire goes right through to the motor by testing for continuity with a multimeter.

To do this properly a suitably rated box and proper cable glands are required.
I do realise this is beyond the expertise and comfort zone many DIYers so I don't encourage this sort of this on these forums.

Yes I could do that. But I must be failing to understand something.
So I'd end up with the magnetic switch on the wall mounted in a extra insulated box. OK.
I presume you left out the part about adding a remote to sit next to the this mag switch and also mounted in/on this insulated box? That that what you meant?

I'm not sure what the electrician would think of a magnetic switch controlling a GPO but I don't see any problem with it.

Then I'd need a 1.5mm^2 flex to the DE. And I'd also add an extra regular isolating switch on the dusty itself for good measure.

Originally Posted by malb

I would not use a supermarket/hardware store mains remote unit for this application as they are rated 10A max current and that is around the operating current for your system. These motors have high start up currents and I have known the relay contacts in the supermarket/hardware store units to end up to be either burnt out or welded in the on position if expected to repeatedly handle large start up currents or stop large motors.

If you can access a sparky willing to work with you on the project, it would be worthwhile from a piece of mind aspect if you are unsure about things.

THIS! I had not thought about that. I was definitely going to use one of those retail plug in remote units. Are you sure they are sensitive to the start up current?
You make a good point about it being a simple circuit but I don't want to stuff around trying to source the right transformer and relay and yada yada. The reality is that would take me a month of Sundays to get around to doing. Which means it won't happen.

I have found a unit on eBay with a relay rated peak load 30A, rating load 15A. That should do the trick. It's not sealed from dust. I'm not sure if that is because it needs air circulation or not. I guess so.

I think If I'm going to use this to control a GPO then I really need to think about paying the electrician to sign off on it.
I could buy it and mount it and let him wire it. That will only take him 10 minutes but it's the call out fee.

Is there another way I could deal with the flex to the DE without using a GPO and a lead?
The DE is on wheels and I want the option, in future to be able to wheel it out the door (under a carport) so I need a approx 4 meters of flex.

BTW, what is the point of having a magnetic switch on a dust collector?
It's total overkill.
When I think about it, my first step should be to simply swap out the magnetic switch with a on/off switch. I had better check how many poles it has first.

The easiest way would be to simply tape the ON button down and the switch it at the power point.

Originally Posted by DaveVman

BTW, what is the point of having a magnetic switch on a dust collector?
It's total overkill.
When I think about it, my first step should be to simply swap out the magnetic switch with a on/off switch. I had better check how many poles it has first.

Definitely not over kill. At the mens shed the impeller jammed on an old DC7 (on which the magnetic switch had been replaced by a light switch) after it sucked up a rag with a piece of wire tangled in it. The motor overheated and the thermal cut out switch kicked in and turned off at the motor . Muggins McDope cleared the blockage without turning it off and disconnecting at the GPO. He was just about to stick his hand back up the impellers jaxi to see if he feel any more debris when the thermal cut out switch switched back out. If Muggins had his arm inside the impeller it would have ripped his arm off. The same think can happen on table saws, not necessarily jamming but overheating from overloading.

Originally Posted by DaveVman

I have found a unit on eBay with a relay rated peak load 30A, rating load 15A. That should do the trick. It's not sealed from dust. I'm not sure if that is because it needs air circulation or not. I guess so.

Be VERY careful about FleaBay electrical relays for power applications. Just Google Counterfeit Fotek & see the fire disasters! (e.g. check this link for a warning https://hackaday.com/2018/08/24/fail...spectacularly/ or thi https://aussiehomebrewer.com/threads...ur-gear.90323/)

Originally Posted by RossM

Be VERY careful about FleaBay electrical relays for power applications. Just Google Counterfeit Fotek & see the fire disasters! (e.g. check this link for a warning https://hackaday.com/2018/08/24/fail...spectacularly/ or thi https://aussiehomebrewer.com/threads...ur-gear.90323/)

Some failures are probably more related to the fact that they are solid state relays than their cheapness.
When they say "max current is 25A" they do mean 25A and not 26A let alone anything above this.
Solid state relays are very poor at handling start up currents and over time will fail if the machine attached is constantly turned on and off.
Electromagnetic relays are better at handling overcorrects but they are not immune to eventual failure

The other issue is the unclear power descriptions used, ie peak, average power, continuous, momentary power etc.
I recent purchased a very cheap light dimmer with a large built in heat sink and a fan rated at max power of 4800W and continuous of 2400W.
By accident it turned out it could handle 4800W for a couple of seconds before the circuit breaker opened.
I then ran a motor from it at around 2200W for about 30 minutes and the dimmer did not get hot so this one seems to be accurately rated.

Originally Posted by BobL

Some failures are probably more related to the fact that they are solid state relays than their cheapness.
When they say "max current is 25A" they do mean 25A and not 26A let alone anything above this.
Solid state relays are very poor at handling start up currents and over time will fail if the machine attached is constantly turned on and off.
Electromagnetic relays are better at handling overcorrects but they are not immune to eventual failure

The other issue is the unclear power descriptions used, ie peak, average power, continuous, momentary power etc.
I recent purchased a very cheap light dimmer with a large built in heat sink and a fan rated at max power of 4800W and continuous of 2400W.
By accident it turned out it could handle 4800W for a couple of seconds before the circuit breaker opened.
I then ran a motor from it at around 2200W for about 30 minutes and the dimmer did not get hot so this one seems to be accurately rated.

Yes. The Chinese write on them a certain current. Only by researching do you discover this is the peak current - NOT the max continuously operating current. They seem to think it is clever marketing to quote the highest possible number they can find in the spec sheets.
The one I am looking at buying includes an electromagnetic relay and I've gone and got the spec sheet for the relay. It's all in Chinese. Which I can't read. However I am certain the 30A figure refers to peak load. It is claimed elsewhere that the max rated current is 15A / 240VAC but I can't really make that out from a spec sheet all in Chinese. I figure 10A of continuous current for the DC should be fine.

Originally Posted by BobL

Definitely not over kill. At the mens shed the impeller jammed on an old DC7 (on which the magnetic switch had been replaced by a light switch) after it sucked up a rag with a piece of wire tangled in it. The motor overheated and the thermal cut out switch kicked in and turned off at the motor . Muggins McDope cleared the blockage without turning it off and disconnecting at the GPO. He was just about to stick his hand back up the impellers jaxi to see if he feel any more debris when the thermal cut out switch switched back out. If Muggins had his arm inside the impeller it would have ripped his arm off. The same think can happen on table saws, not necessarily jamming but overheating from overloading.

Mmmm OK. I didn't imagine someone sticking their hand inside a machine while it's still plugged in. You make a good point.

Although if I remove the mag switch and set that on the wall, then any future owner of this machine will be required to engage brain before usage anyway.

I could replace the mag switch with a regular toggle switch that has a light in it. That way, Muggins McDope will have the option of noticing a lighted switch if he likes his hand. Of course if he is running around, sticking his hand inside powered machines, he might not be deterred by a lighted switch - which is on the other side from the intake.
Then again, the only other flesh eating machine in my shop with a magnetic switch is the table saw. Everything else in the shed, is just dying to chop someone's digits off.

Originally Posted by DaveVman

Yes. The Chinese write on them a certain current. Only by researching do you discover this is the peak current - NOT the max continuously operating current. They seem to think it is clever marketing to quote the highest possible number they can find in the spec sheets.
The one I am looking at buying includes an electromagnetic relay and I've gone and got the spec sheet for the relay. It's all in Chinese. Which I can't read. However I am certain the 30A figure refers to peak load. It is claimed elsewhere that the max rated current is 15A / 240VAC but I can't really make that out from a spec sheet all in Chinese. I figure 10A of continuous current for the DC should be fine.

Depending on how "bored out" the opening is, the "start up currents" on a DC7 are at least 35A so if you use a 30A peak load SS relay and continually switch it on and off - which happens with dust extractors - then in time that SS will die. I've cooked several of those cheap 30A SS relays on my remote DC switch before attempting to measuring the startup currents which I found were over 60A.
Now even though I have my DC on a 4HP 3Phase motor, its driven by a VFD - so no start up current problems.

Originally Posted by BobL

Open up the existing switch on the DC and note what coloured wires go where (VERY IMPOTANT)

These days the first thing I do on opening up anything electrical is to whip out the cellphone and take a photo. An added benefit of that is if you need advice, you’ve got the photo with you.