Taming DeWalt's electrickery

[Rusted]

Hi

Do we have any qualified electricians who can give me the all clear on wiring an Emergency stop button?

I''m using my DeWalt DW745 mobile table saw for cutting out thin plywood, covering panels for my dome.

The problem is reaching the sub-miniature Start-Stop buttons hidden under the saw's projecting table top and fence rack.

My idea is to use  a commercial Stop button in the extension lead to the saw.

I don't want to modify the saw's wiring in case I void the guarantee. Nor screw on a hinge for a mechanical switch paddle.

The turn-to-release, Big Red, stop button was supplied with a single pole, normally closed, internal switch block.

One can never rely on polarity with a two core, two pin plug, 2x1.5mm^2, mains extension lead.

So I'm going to switch off both Live and Neutral simultaneously.

By adding a second internal [normally closed] switch block.

I was going to fix the sealed switch box to my saw stand where it will be easily accessible.

Is this switching scheme a good idea? Or simply lethal?

All power tools and domestic appliances [in Denmark] use two pin plugs 230V.

I have emailed DeWalt UK to see if I can swap my silly little [European market] push buttons to a US-pattern, big red paddle switch.

But they haven't bothered to answer yet. Presumably the Americans are far more litigious.

 So DeWalt won't get away with hiding such silly little push buttons down under the table over there. [Arrowed]

Thanks, in advance, for any useful advice.

[wxsatuser]

It should be ok as long as you switch both off.
The machine buttons most likely control a no volt release so the machine should go dead and not restart.

Your switch blocks only allow 3amps at 230volts, how much does the bench draw on load?

[Cosmic Geoff]

Don't take this as definitive, but what exactly do you want the big red emergency stop button to do?

If it's to stop the mechanical rotation of the saw and prevent it chewing up wood or removing your fingers, then a single pole switch (of adequate rating for the power being consumed) will do the job.

If it's to electrically isolate the saw in the event of an electrical fault, then you'd want double pole switching. 

[Mick J]

Seems like a good idea to me, I have often toyed with the idea of using a foot switch in cable when using some tools...........

Are you sure the table saw is the tool for the job ?  would a circular saw for example or Jig saw again be better suited ?

You are doing the job and I am trying to be helpful,  short of suggesting a small child turning off the table saw when told may work.

[JamesF]

That does seem like quite a poor design.

I have a table router with similar button positioning, but the stop button protrudes more than the start button and the two are covered by a large flap that can depress "stop" but doesn't touch "start", which makes it quite easy to turn the motor off without needing to see what you're doing -- all you need to do is hit the flap.  There may be negative sides to this arrangement, but thus far I quite like it.

James

[michael8554]

As MickJ says, a foot switch.

But a non-latching action, so when your foot comes off it kills the power.  

Michael 

[Rusted]

Thank you to all who responded. In no particular order:

My hope was that my big red button [BRB] would kill power to the saw in the same way as does the DeWalt red button.

But be far more accessible. It is rated at 3A but 10A thermally. It is advertised and sold as a 10A Emergency Stop switch.

The saw probably pulls a couple of KW on start-up. 10A maximum allowable at the Consumer Unit via a fuse.

MY thinking is that the starting load would still be under the control of the DeWalt green start button.

It was not my intention to restart the saw with the new switch. I imagined a double action:

Power off after each cut on the BRB. The saw stops but will not restart until the green button is pressed.

This requires the BRB is [turn] reset each time.

The BRB effectively becomes the new Off switch. I have yet to discover if the saw will restart automatically from a BRB stop.

One could imagine the BRB works just like pulling the plug with the motor running.

I can check if the saw restarts after pulling the plug but haven't yet.

I m not qualified to judge the loads applied to the switch contacts on switch off.

Emergency stop buttons are normally closed, mechanical push off operated [by law.]

The table saw with sled allows me to remove hair's breadth cuts at tiny changes of angle to perfectly match my trapezoid dome panels edge to edge.

It produces perfectly straight cuts.

[wxsatuser]

The 10amp rating is AC1 type loads only.

Your saw is an AC motor load and the switch should really be AC3 rated.

Generally stop switch blocks go in the control circuit where current is minimal.

 

[Rusted]

29 minutes ago, wxsatuser said:

The 10amp rating is AC1 type loads only.

Your saw is an AC motor load and the switch should really be AC3 rated.

Generally stop switch blocks go in the control circuit where current is minimal.

 

Thanks. It sounds as if you really know what you are talking about.

I'm not sure how they can claim a 3A switch is a 10A switch.

Should I order AC1 blocks to go inside my switch housing?

Or should I put my BRB switch somewhere in the saw's original wiring?

It uses spades and tabs [my terminology] so could easily be added to without attacking the wiring itself.

The following image will probably explain more than I can describe.

There is a small yellow box component just visible in the background behind the switch wiring.

View seen from below:

[wxsatuser]

It's a 3Amp switch at 240Volts AC15, AC15 is electromagnetic loads.
The 10Amp rating is for loads that are purely resistive AC1 rating.

If the controls on the saw have a control circuit with separate wires you could
break them and put your stop button in series with them, if not you cannot do that.

A lot of these machines have an inbuilt no volt release, there is a coil in there that holds the switch on until
you press stop or the power goes off, a safety feature.
Cannot tell from the pics as it's hard to see.

[Rusted]

Thanks, this is useful information. [If I knew how to apply it.]

The leads to the switches and motor are very short, underneath the saw and housed in a black box.

Which make photography very difficult even with flash.

I thought I saw a cylindrical object so that could be the coil you refer to.

Can I just put my 3A Stop Switch in series with that?

 

[wxsatuser]

The coil will be in the bit with all those leads on it.
The top black box is a cutout.

How bit is the cylindrical object?
If it's fairly big it might be a capacitor so don't put the switch in line with that.
Have you got a pic of it?

[Rusted]

Give me a quarter of an hour and I can open up the wiring box again.

I'll try to get a more useful image of every object in there if I can.

The largish black object with single red and white wires is the [thermal?] reset button on the front of the saw casing.

I'll be back.

[Rusted]

Hi again. I very grateful for your help in sorting out this lot..

I have photographed each component. There seems be two clear 'capsules' not one.

The yellow "box" is labelled as seen below:

Let me know if you want more images I have left the box open just in case.

[wxsatuser]

The first pic, yellow item is a capacitor think these are normally suppression type.
The black item is a cutout trip.

The last pic is the no volt release, coil connected across output, switchs off when power loss.
The coil is internal to the switch normally and not accessible.

[Rusted]

Thanks very much for identifying those parts.

The last pic was the yellow label on the side of the main [push button] switch.

Cables are brown/blue in and brown/blue to the motor.

But what are the two clear "capsules?"

Thermal cut-outs?

Is there anywhere I can usefully insert my BRB safety switch?

Or shall I just make a hinged [hanging] plywood lever to operate the DeWalt RED push [Off] button mechanically?

Thanks

[wxsatuser]

The clear items just look like connectors, do they pull apart?

May be a simple lever would be best instead of messing with the stop button.
or
Get 16Amp contact blocks for you stop button, if you can find some.

[CraigT82]

Sorry can't help with the electrics... but the most recent crosscut sled I made for my table saw I only bothered with one runner rather than two... much easier to make the sled with one and just as accurate I've found! 

[Rusted]

51 minutes ago, CraigT82 said:

Sorry can't help with the electrics... but the most recent crosscut sled I made for my table saw I only bothered with one runner rather than two... much easier to make the sled with one and just as accurate I've found! 

Thanks for the idea but my sled is 90W x 70D to cope with my 60x50cm dome panels.

I even had to fix a runner to the fence racks to support the left side and avoid the whole lot tipping.

[Rusted]

54 minutes ago, wxsatuser said:

The clear items just look like connectors, do they pull apart?

May be a simple lever would be best instead of messing with the stop button.
or
Get 16Amp contact blocks for you stop button, if you can find some.

I'm searching for 16A blocks but nothing so far.

My original supplier has only the 3A type.

I have confirmed the motor remains off when I pull and reinsert the mains plug [as expected.]

[Stub Mandrel]

That does appear to be a no-voltage release switch (NVR) i.e. if you switch off the power it won't restart unless you press the green button.

If it works like this the best option is to wire a push-to break mushroom stop switch between that switch and the power lead. If it doesn't work like this, replace it!

The e-stop can be single or dual pole, as long as it breaks the current it will reset the NVR.

If instead you fit a combined e-stop/NVR you shoudl remove the existing switch.

You should only have one NVR switch in the system, but as many e-stops as you want as long as they break the current before the NVR.

 

[Rusted]

Hi and thanks for your input.

The problem seems to be the claimed 10A rating of my mushroom emergency stop switch is only 3A for motor loads.

I have confirmed the motor does not restart if I pull and refit the plug while the motor is running.

The NVR seems to be internal to the DeWalt press button switch unit according to an earlier response from wxsatuser.

There is another 3A internal switch block coming in the post so I can cut the power to both +/- mains conductors simultaneously with my red mushroom.

Are you suggesting I can safely insert my 3A mushroom emergency switch in the extension lead to the saw?

To do so would be to ask my BRB switch to carry nearly 2Kw continuously and more during start-ups.

Or have I misunderstood?

[Stub Mandrel]

18 minutes ago, Rusted said:

Are you suggesting I can safely insert my 3A mushroom emergency switch in the extension lead to the saw?

To do so would be to ask my BRB switch to carry nearly 2Kw continuously and more during start-ups.

Alas no, the mushroom needs to be rated 8A or 10A continuous for that saw.

I would fit one in the supplied power lead and attach it to the body of the saw.

Otherwise as @wxsatuser

 suggests you may be able to fit the switch you have in series with the stop switch on the existing NVR, but that requires a bit more of (1) 'being sure what you are doing' and (2) this actually being physically possible.

The easiest solution is this combined start/stop and e-stop switch from Axminster rated at 15 Amps which would completely replace the existing switch. there are no doubt cheaper options...

https://www.axminster.co.uk/kedu-nvr-switch-230v-1ph-e-stop-200093

[Rusted]

Hi Neil.

Thanks for the useful suggestion.

My supplier lists exactly the same item, with a different manufacturer's label, but doesn't give its rating in their sales blurb.

It makes good sense to have all start/stop/STOP! buttons easily accessible.

Is anyone familiar with these cable entry glands?

Can they be easily/manually released to save me making more holes?

[Stub Mandrel]

You can probably squeeze them on the far side and pull/wangle them out. Expect a bit of a tussle.