Fitting a soft start module to Dewalt DW745 table saw

[Stevekane]

Many thanks Martin, (and Sam) Ive ordered one up, ebay £16.50,,with lots of good feedback from people fitting them to saws,,if I dont blow myself up I will let you know how I get on,
Steve.

 

[Amclaussen]

So I have just finished fitting it and it works well - The startup takes about 1-2 seconds max, and is much less traumatic than it was prior to this (anyone who has one of these type of machines will know just how abrupt the start is). The startup is now rather similar to my Festool TS55.

It was a bit of trial and error in the end as it appears the XS-16/D3 wiring is slightly different to the XS-12/D3.

I will write up how I did it into a small article with some photographs and a before/after video shortly, possibly this evening or tomorrow at some point.

I will wait for it!... Another important point that appears that it has not been mentioned yet: Is it reducing the inrush current too? (having a soft-start is nice indeed, but limiting the start-up current peak is perhaps more important in many installations!

 

[TomGW]

I will wait for it!... Another important point that appears that it has not been mentioned yet: Is it reducing the inrush current too? (having a soft-start is nice indeed, but limiting the start-up current peak is perhaps more important in many installations!

This would be my question too.
I have a SIP 01332, bought used and fitted with a 13A plug/fuse. It normally runs fine but will occasionally blow the fuse on start up. I see that they are supplied new with no plug fitted and a 16A supply needed. I’m wondering if a soft start module would resolve this (very occasional) issue?

 

[Stevekane]

Look boys,,,I really know nowt about electrickery and my reply is just by way of friendly chit chat and my own curiosity, but my guess would be that they could help, however it would mean you buying one rated at the ampage you would need. My little saw has a 1500watt motor, at 240 volts thats drawing about 6 or 7 amps and a little more at startup, the soft starts are from memory rated at I think 16amps so were well within its capability,,but if your machine is knocking out a 13amp fuse I would think its possible that its drawing at least or more than 16amps,,,what do people more knowledgeable think?
Steve.

 

[MorrisWoodman12]

...Another important point that appears that it has not been mentioned yet: Is it reducing the inrush current too? (having a soft-start is nice indeed, but limiting the start-up current peak is perhaps more important in many installations!

Yes I think it should though I'm more electronicery rather than motorery. The surge is produced because is no back-emf from the non-spinning motor so the inductance of the windings appears as a virtual short across the supply. Note that any inductance tries to keep the status quo i.e. it only allows the current to increase 'slowly'. The slow start triac is only turned on for a fraction of the mains half cycle keeping the surge low but doesn't eliminate it. Hence as the slow start time passes the triac is on for a greater fraction of each half cycle, the motor spins up, the back-emf increases reducing the surge until the current drawn by the motor stabilises at its running current.
Well I think that is how it should work but I stand to be corrected.
And yes I'd like to reduce my surge and frequency of 13A fuse blowing too.
Martin

 

[Stevekane]

Hi, finally got around to fitting the Soft Start module to my Excell site saw and its made a tremendous difference, a soft click as the NV swich engages followed by a gentle whiz up to full speed, no knocks and bangs making you jump, so Im very pleased indeed. My one came from ebay, Ive posted the link to the advt, it looks the same as the one above and was just £16.50 inc postage and came with a simple wiring diagram which I followed. One thing I did differently was that I didnt cut or alter any of the wireing, Im fortunate in that I have a set of crimping pliers, nothing fancy, but the type that properly folds and crimps terminal onto the wires like the factory does, and I was able to just crimp on the appropriate terminals to the module so that it connected onto the existing wireing, worth bearing in mind if you dont fancy cutting the wireing on your expensive saw or tool around.
Steve.
https://www.ebay.co.uk/itm/26566199...id=DV2cOgfBRTS&widget_ver=artemis&media=EMAIL

 

[stuart little]

My module appears to have conflicting markings, they're so faint I had to decipher them in bright sunshine, then re-draw them on a lable. I'm now completely baffled over the wire colours, mine being red, blue, black, & in difference sequence - HELP!

 

[rogxwhit]

I have a SIP 01332, bought used and fitted with a 13A plug/fuse. It normally runs fine but will occasionally blow the fuse on start up. I see that they are supplied new with no plug fitted and a 16A supply needed. I’m wondering if a soft start module would resolve this (very occasional) issue?

I don't know what your installation is in terms of cabling and distance, but long runs can lead to voltage drop which affects the current draw and this can be a triggering factor in fuse blow at startup when things are marginal. If the saw was a long way from the CU across the yard to a garage, for instance, even in 2.5 cable - or on a long extension. Worth reviewing whether that's your issue.

 

[sams93]

My module appears to have conflicting markings, they're so faint I had to decipher them in bright sunshine, then re-draw them on a lable. I'm now completely baffled over the wire colours, mine being red, blue, black, & in difference sequence - HELP!

Hi - Have you read the guide above with the photos? - the module i installed is identical to the one you have

 

[sams93]

DISCLAIMER – I DO NOT RECOMMEND THAT ANYONE ATTEMPTS TO DO THE MODIFICATION DESCRIBED IN THIS POST THEMSELVES. MAKING ALTERATIONS TO ELECTRONICS SHOULD BE LEFT TO APPROPRIATELY QUALIFIED ELECTRICIANS, AND IS NOT A DIY TASK. THIS IS SIMPLY A DOCUMENTATION OF WHAT I DID TO MY SAW, AND DOES NOT CONSTITUTE ADVICE/INSTRUCTION/RECCOMENDATIONS FOR OTHER PEOPLE TO DO IT. PEOPLE SHOULD NOT ATTEMPT TO OPEN OR MODIFY THEIR ELECTRONIC DEVICES, AND THEY SHOULD REFER TO THE INSTRUCTIONS AND MANUFACTURER FOR ADVICE. I ACCEPT NO RESPONSIBILITY FOR ANY INDIVIDUAL WHO ATTEMPTS TO MODIFY THEIR OWN ELECTRONIC DEVICES, WHICH THEY DO AT THEIR OWN RISK.



So I got round to fitting the soft start and I am pleased with the difference it has made. Having read some articles and watched some videos online I thought I would have the hang of how it needed wiring, but it turned out this module wiring was slightly different.

My saw is an EXCEL 7471 210mm 1500w site table saw ( Excel 210mm Portable Table Saw 1500W). It cost me £130 from the Tools4Trade website. It is extremely similar to the DeWalt 7485 as far as I can tell. It has an extremely aggressive start-up which is common for the budget end of this type of saw. I wanted to add a soft start module to reduce the number of heart attacks that I receive upon turning the saw on. The saw has a no-volt release on/off switch, and a resettable thermal fuse. Below is a video of the saw as it comes without a soft-start.

View attachment 135470














There are a couple of soft-start modules available currently in the UK. The one I used was an XS-16/D3 (Similar to the XS-12/D3, but the XS16 is rated at 16a, and has slightly different wiring apparently).

I started by ensuring everything was unplugged. I released the plastic bars from the switch back box which secure the power cable and the cable to the motor.
View attachment 135471

I then removed the 4 philips head screws from the front of the switch assembly.
View attachment 135472

I then examined the rear of the switch and contents of the switch back box. There were three components to note.

• A Push to Reset Thermal Fuse (Input is attached to the Neutral (Blue) of the Power Cord, the Output RED is attached to the Neutral side of the switch).
• A No-Volt Release Switch – there are two sides. The Live side input is from the BROWN power cord, the output is to the neutral BLUE side of the motor cord. The neutral side input is from the RED cable from the thermal fuse, the output is to the BLUE cable to the motor. (Annoyingly I did not take a photograph of this).
• A Yellow Capacitor – wired in between both the Live and the Neutral of the cable to the motor.

Having read some articles where people had wired a soft-start to the Power Input side of the switch (which required the NVR switch to be held down during starting), I decided to wire it into the Motor Output side of the switch to avoid this issue.

Connections were made using crimped connectors, and two layers of heatshrink tubing was used to cover any exposed connections. RED was used for Live and Blue for Neutral. Multiple layers of tubing were applied to ensure that the outermost colour was correct, where it was not possible to use a single layer in the appropriate colour due to the sizes of tube I had.

Overall I used 1x female spade connector, 1x male spade connector, and 1x in-line connector.

On the XS-16/D3 Soft-Start Module there are three wires:
View attachment 135473View attachment 135474

A – Blue (Connected to neutral on the Motor Side via an in-line crimp).

B – Red (Connected to the Live on the Motor Side of the Switch using a Spade Connector, now covered in red.

C – Black (Connected to the Live on Motor Side using a Spade Connector now covered in red)

In simple terms, the Red (B) and Black (C) were connected in line from the switch live output (red) to the live wire to the motor (red). The Blue (A) was then connected to the Neutral (Blue) wire going to the motor.

A diagram is below showing how this was done, and there are some photographs of how it was wired in.
View attachment 135475
View attachment 135476
View attachment 135477

The Soft-Start module was then placed inside the back box of the switch, the switch reassembled, and the cable clamps re-applied to secure the cables.

And that was it. The machine was plugged in and now operates with a soft-start. I do not have to hold down the switch to turn it on, simply press it once. It starts similarly to my Festool TS55 with a short whirling noise and reaches full speed in about 1-2 seconds. I no longer experience coronary events on turning on my table saw.

There is a video below of it with the soft-start fitted:
View attachment 135478



















I re-iterate the disclaimer from the start – I really DO NOT recommend that anybody tries this themselves. Electrics should be left to experts, and users should not attempt to open or modify these machines which are dangerous.

This

 

[stuart little]

Thanks Sam, yes, after spending several more frustrating hours watching different YT vids, I eventually found one pertaining to my DW745 wiring, I found that there are a few variations over the years, & reviewing your 'layout' with a brain cleared of 'fuzzy ness' by watching the events of yesterday, " Eureka"- as the man said. Just remains now to get it done.

 

[John Brown]

Bit late to this thread, but:
Do these things work on induction motors?
Would they be of value in trying to run my 1600W saw from a pure sine wave inverter?

 

[sams93]

Bit late to this thread, but:
Do these things work on induction motors?
Would they be of value in trying to run my 1600W saw from a pure sine wave inverter?

Hi John,

When I first started my shed (had no idea i would get into woodwork), I had a power system which consisted of 3 x 200ah leisure batteries, connected to a 4000w (2000w continuous) pure sine wave inverter.

I have a 400w induction motor on my bandsaw, and found that it would run noisily and harshly, I wasn't happy with it at all. I also found that the load that this put on the batteries meant that they were drained in a much shorter time than I had calculated they would.

I don't know if maybe my 'pure sine wave' inverter was producing a less-than pure sine wave or what, because theoretically at least it shouldnt have been any different to mains AC.

With regards to the soft-start module, I don't know about that one!

Sam

 

[John Brown]

Hi John,

When I first started my shed (had no idea i would get into woodwork), I had a power system which consisted of 3 x 200ah leisure batteries, connected to a 4000w (2000w continuous) pure sine wave inverter.

I have a 400w induction motor on my bandsaw, and found that it would run noisily and harshly, I wasn't happy with it at all. I also found that the load that this put on the batteries meant that they were drained in a much shorter time than I had calculated they would.

I don't know if maybe my 'pure sine wave' inverter was producing a less-than pure sine wave or what, because theoretically at least it shouldnt have been any different to mains AC.

With regards to the soft-start module, I don't know about that one!

Sam

Thanks. That's useful. The inverter I'm looking at is 4000W continuous/8000W peak. My usage is hobby only, and mainly hand tools.
I'd be curious as to the model of inverter you used, as you say, it may not have been that "pure".

 

[sams93]

So mine was a cheap chinese brand, I would hazard a guess that something like a victron phoenix would maybe give much better results, but they are a hell of a lot of money!

I think there are two problems (although I am not an electrician):

1. The motors on our machines draw huge initial currents which most inverters really struggle to handle

This makes the startup very harsh/jerky and sometimes even unsuccessful. My planer actually wouldnt start at all it just jerked around. In my experience some no volt release switches also don't work well in these situations. The incredibly high inrush currents for motor starting is the reason that some of us have to put type C breakers in on their consumer unit to cope with the inrush current of machine motors starting up.


2. The batteries supplying the inverter don't like it either

A car battery is great at providing the initial high current needed for a motor, and in theory would be great for managing the brief initial inrush, but they are absolutely terrible for providing power over a longer period, even like 5 minutes or so they struggle.

Leisure batteries are much better at providing the power over a longer period, but arent very good at handling the initial high current required for startup.

You might get some better responses from others if you start a new thread in the main 'general woodworking' forum with your specific question as I imagine less people are inclined look at this post who have expertise on what you are asking.




What I would suggest is that you try your machines out on someones first before buying, appreciate that might be a bit inconvenient (maybe you could find someone locally with a campervan or something with the inverter youre thinking about installed), but in my experience my whole set up turned out to be a waste of money and in the end I just ran a 6mm armoured cable from my consumer unit to my workshop and everything was much better - I just wish I had done that from the off.

 

[John Brown]

I would need a trench about 50m long, but the main problem is that the electrician won't connect is, as we are already at maximum for the incoming power. Upgrading that would cost a fortune.

 

[okeydokey]

Would a small petrol generator cover your needs?

 

[sams93]

I would need a trench about 50m long, but the main problem is that the electrician won't connect is, as we are already at maximum for the incoming power. Upgrading that would cost a fortune.

I am wondering if you could do it as a fused spur off one of your ring mains, then you wouldn’t need to wire it in separately to the CU.

I don’t think that is the ‘ideal’ way to do it, but I think it might be within what’s allowed, there’s no limit to the length of a *fused* spur off a ring main. Should be sure that the circuit is RCD protected as well. Obviously the best thing would be to talk to electrician about the idea and there are plenty of forums which will advise you on whether that is within regs etc, then could propose that to electrician?

You would be limited to 13a for the fused spur so depending on what you’re running might be an issue. And 50m of SWA isn’t cheap, nor is a digger for a trench (I did my 35m one by hand in a day and a half, but it was some serious work and I would hire a digger if I did it again!!), but depending on how often you plan to use the workshop etc it might be worthwile.


If all that seems too much, then I think the petrol generator idea that OakeyDokey has suggested would be something well worth looking into rather than an inverter off batteries.

 

[John Brown]

Generator would be a possibility, but I now have most of the kit for solar charged batteries and inverter. I will see how it works out. I'm hoping that fitting soft start modules to the table saw and the bandsaw will help.
As for a fused spur, the nearest and by far most convenient circuit is actually a 16A radial circuit, which is what my 50m extension cable is plugged into currently, but it can trip if certain appliances are turned on in the house.

 

[sams93]

Generator would be a possibility, but I now have most of the kit for solar charged batteries and inverter. I will see how it works out. I'm hoping that fitting soft start modules to the table saw and the bandsaw will help.
As for a fused spur, the nearest and by far most convenient circuit is actually a 16A radial circuit, which is what my 50m extension cable is plugged into currently, but it can trip if certain appliances are turned on in the house.

Let us know how you get on with the solar system you put together - I would be really interested to know if you manage to get it to operate well! I would expect the van conversion forums/people might have really good advice on these setups as they do them all the time for their vans.

Out of interest how big a battery bank have you planned for? I had 2x110ah Class B leisure batteries wired together in mine - as I say that was woefully insufficient in my case, but my solar panel was small and the inverter was cheapish, so there could have been multiple bits at fault as well!