Fitting a soft start module to Dewalt DW745 table saw

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sams93

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I found two modules to be available on eBay at reasonable prices (<£20).

One is an XS-12/D3 - which is rated at 12a.

Then there is also an XS-16/D3 which appears to be very similar just rated at 16a.

both of those are 3 lead modules, which appears to consist of a line in, line out, and neutral.

there is also a 2 lead module available through Amazon, which appears to just need wiring in-line with line supply, but this type hasn’t appeared in any of the videos or articles I’ve read so i purchased the 3 lead XS-16/D3.

Hopefully should arrive this week.

EDIT:
I also found a 3 lead module available through a more reputable looking source(link below). It is about £15 and appears to be the same as the 16a XS-16/D3. If I had found this before I’d ordered the other one I probably would have gone for this one.

link - Sealey Mg314.V2-93 - Soft Start | AMP-Starters

Just as a matter of intrest but I think Ive seen different spec modules being used, from memory, but I might be wrong, 15 amp or 25amp and Ive also seen videos where the saw starts really softly building up speed over 2 or 3 seconds wheras others seem to still fire up rather suddenly,,is there an idea rated module for certain motor sizes perhaps?
Steve.
 

Spectric

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I would seriously question the need to modify a machine and fit any aftermarket device such as these softstarters. Many already have a softstarter built in, but I can see the point with handheld machines but a tablesaw!

Only once it's at full speed will the current through the saw be enough to hold the NVR's magnetic switch closed and keep the power on.
That would not apply if you use a proper DOL starter, only if using one of those cheaper switches that are used on so many of our machines.
 

Sideways

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We are talking about a DeWalt.
They are experts when it comes to value engineering :)

More seriously, there are circ saws out there powered by circa 2kW brush motors that start with a truly brutal noise and kick. It doesn't much matter whether handheld or tablesaw, I do have every sympathy with owners who find this obnoxious and would like to tame these machines.

In my own history I've owned a 9" hitachi handheld which fell into the brutal category and the Metabo 1650W KSE series handheld that had soft start, variable speed and constant speed under load electronics built in. The Metabo is soooo much better.
 
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Stevekane

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I would seriously question the need to modify a machine and fit any aftermarket device such as these softstarters. Many already have a softstarter built in, but I can see the point with handheld machines but a tablesaw!


That would not apply if you use a proper DOL starter, only if using one of those cheaper switches that are used on so many of our machines.
Spectric, Is it so different to fitting a better blade? people are not removing safety features or repurposing anything, not doing anything that the manufacturers don't routinely do themselves but they wanted to save a few extra pennies with our machines, and the result is removing the sudden violent start up which must play havoc with gears and things, the saws we are looking at have no soft start built in, as you say many do, but its great to discover you can enjoy soft start on your saw for a bit less than £20. Im a bit surprised anyone could think thats wrong?
Steve.
 

Sheptonphil

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Abut to add one to my Dewalt Dws774 mitre saw. The saw’s OK, but the startup is just plain violent and snatch.
has anyone frites it to the 774 and know the waiting pin out?

hanks
 

clogs

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Vamos, Crete, GREECE.......
sheptonphil
chips with everything.....lol....

My DeWalt 708 will get one, thats if there's a 110v version.....?
anyone know......?
mines nasty on start up......and I use it a lot.....
 

sams93

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sheptonphil
chips with everything.....lol....

My DeWalt 708 will get one, thats if there's a 110v version.....?
anyone know......?
mines nasty on start up......and I use it a lot.....


Although it looks identical to the 240v version so I wonder whether they would be interchangeable. Saying that, I’d still get the one being sold at the voltage of your machine though.
 

sams93

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So the module arrived today. If I get time I will give it a go this evening. I did pry the metal heatsink slightly to peep inside, theres a transistor and a single resistor, I cant open it up fully to photograph because the metal is actually a heatsink attached to the transistor and I dont want to flex the legs too much.

Will post updates as i go.


IMG_4143.jpg

IMG_4142.jpg
 

Sideways

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That looks like Live in on red (B), Live out on black (with the soft start ramp up), and Neutral reference on blue.
It won't be a transistor inside, it will be a device called a triac, SCR or similar but they use the same 3 wire packages as transistors so you can only tell them apart by looking up the numbers printed on the device itself.
Nice to have a clear diagram :)
(y)
 

sams93

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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.
 

sams93

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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.
















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.
4c93fa70-10b2-4104-b6b2-ba5cc61a4bce.JPG


I then removed the 4 philips head screws from the front of the switch assembly.
c9a1636d-fd04-4ff6-bb4b-65e60fb6d2ce.JPG


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:
IMG_4142.jpg
IMG_4143.jpg


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.
cc19ccab-7e2d-4d85-aaa0-51f9d53deb39.JPG

9c8f7fce-143b-4619-839b-bf0c1eeb2a05.JPG

7a471df3-c281-4091-89d9-8e5f7dd6b860.JPG


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:




















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.
 

Sandyn

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Just a friendly caution about these modules. There is no way of knowing how they are constructed internally and how they will fail. Since there is no earth, I would treat the whole module as if it has the capability of going live when it fails. Even if the metal has high impedance to all three connections, the insulation may fail. Worst case, the metal heatsink could go live. The module will be inside the housing, but just be careful
 

OCtoolguy

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Pardon me for asking this but since I have a DW745 here in the U.S. where we are on 120v A.C. I'm not sure if I have a problem or not. I've not noticed any "hard" start issue with my saw but maybe I'm just not bothered by it. Have any of you folks any knowledge about my saw or my situation? Should I be adding a "soft-start" module to my saw? It does come on quite strong but I just thought it was the nature of the beast. I've very happy with its performance.
 

MorrisWoodman12

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Just a friendly caution about these modules. There is no way of knowing how they are constructed internally and how they will fail. Since there is no earth, I would treat the whole module as if it has the capability of going live when it fails. Even if the metal has high impedance to all three connections, the insulation may fail. Worst case, the metal heatsink could go live. The module will be inside the housing, but just be careful
I agree with @Sandyn . From past experience it is difficult to get reliable insulation between the triac and its heatsink unless the triac is of the sort which is fully insulated by design. But just wrapping the whole thing up in heatshrink tube or insulation tape ruins any possibility of heat flow away from the triac. A true catch 22. However the triac is really only going to be dissipated during the couple of seconds while the motor comes up to speed so you'll probably get away with it.
On a slightly different note if I were designing a beast such as this I would connect the triac directly to neutral. The motor would then be connected directly to live and the slow start device would need/have a live 'reference' connection. Unfortunately the mounting/heatsink tab is generally connected to the load i.e. motor in this case so that, if there is no insulation or its failed, would make the heatsink live when the device is off. Connecting the other way around would keep the heatsink at neutral. But that's not a situation to rely upon nor would it pass any safety standards testing.
I would strongly recommend that this device is placed after the main machine switch/NVD from a safety standpoint.
Just my rambling thoughts on the subject. I'll go drink my tea now.
Martin
 

Stevekane

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I could be wrong but I think our friend Sam has indeed wired the module after the switch,,so unless you were trying to operate the saw with the NVR switch dismantled there seems to be little opportunity of coming into contact with the heat sink?
BTW sam, thats a great write up and really helpful and appreciated, many thanks indeed, I will get on and order one for my Excell saw.
BTW but from memory the Sealey one you linked to didnt look like there was a metal heat sink, looked to be all plastic? I recall thinking that I rather liked the bit of metal but maybe not such a good idea after all!
Steve.
 

sams93

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I could be wrong but I think our friend Sam has indeed wired the module after the switch,,so unless you were trying to operate the saw with the NVR switch dismantled there seems to be little opportunity of coming into contact with the heat sink?
BTW sam, thats a great write up and really helpful and appreciated, many thanks indeed, I will get on and order one for my Excell saw.
BTW but from memory the Sealey one you linked to didnt look like there was a metal heat sink, looked to be all plastic? I recall thinking that I rather liked the bit of metal but maybe not such a good idea after all!
Steve.


Yes I wired it in after the switch and it works fine. I actually did it that way because others had explained that if it is wired in before the switch the button had to be held down fully during start up or would turn off.

I have read the last few posts with interest, and wonder whether I should try and seat the module in something separately, or cover it in a big piece of heat shrink. I’m not sure that it would have too large an effect on the heat dissipating ability, I’d welcome thoughts?
 

Stevekane

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Far from it for me to offer electronics advice,,but I would guess that the module is only creating warmth for the few seconds of start up, once your at full speed no or very little heat would be created??,,happy to be corrected on this though.
And I think that on the write ups Ive seen concerning these things they are often fitted by the manufactures inside the handle on chop-saws or inside the switch on tablesaws,,,
Steve.
 

MorrisWoodman12

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Yes I didn't mean to imply @sams93 was wiring it incorrectly but I had seen other posts suggesting the slow start could be wired before the NVD. Also I did suggest that the slow start will only dissipate for the second or two that the slow start is operational and thereafter only a minimal dissipation so, yes, @Stevekane your advice is correct.
Have fun
Martin.
 
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