Adding a Current Transducer + contactor to my 230v table saw

[Prizen]

Hello all

In an effort to make my Henry vac auto start with my DeWalt DW745 table saw, from reading previous threads here's how I think it can be done. Just looking for some guidance perhaps from someone more knowledgeable with electrics than I:

Buy a current sensing device (current transducer) and an electrical contactor (say 20 amp rated).

Cut cable on table saw between NVR switch and motor.

Run live wire through the current sensor orifice. Wire up the current sensor to the contactor.
Wire a socket to the contactor.

Plug in Vac to new socket and power on, when table saw starts then current sensor activates the contactor coil, which gives power to the socket so the vac starts.

Does this make sense?

 

[sunnybob]

http://wiki.diyfaq.org.uk/index.php/Cur ... _collector

Towards the bottom of the article it mentions dust collectors

 

[Sideways]

Depending on what you buy, your current transducer may need an amplifier to drive it. The current sensing coil is a low power passive device and needs some electronics to turn its output into a stronger switched output (either at mains voltage or at 24v) that will drive the contactor coil.
Perhaps you can get the sensing coil and electronics packaged together.
In either case, i just wouldn't bother. Get a radio remote control mains switch, hang the remote fob on the corner of your saw and do it manually. This is easy, cheap and when you are batch cutting you don't need the vac constantly starting and stopping so in some ways it's actually better.

 

[Myfordman]

This works. http://www.thewoodhaven2.co.uk/viewtopi ... =22&t=4284

 

[Prizen]

Thanks it was the woodhave article I was trying to interpret actually! It doesn't appear too complicated.

I like the RF remote idea, but every second counts so would prefer a completely automatic power on/off

 

[deema]

I might be missing a something here, but why bother with the current sensor?

If the NV switch has the load capacity just wire after the switch to a socket for the Hoover. If it doesn’t, just wire the activation coil of a contactor to the output side of the NV switch.

 

[John Brown]

I'd be wary of a website that advocates such a solution for a bathroom fan, when a humidistat would do the job...

 

[Prizen]

I might be missing a something here, but why bother with the current sensor?

If the NV switch has the load capacity just wire after the switch to a socket for the Hoover. If it doesn’t, just wire the activation coil of a contactor to the output side of the NV switch.

I think you are right on the money. I guess as I have the NVR switch then that takes away a current sensor requirement.

I've done some research on the NVR in the DeWalt and I think it is just sized just enough for the saw motor.

So I assume I need to proceed as follows

I tap in a contactor in the run between NVR switch and the saw motor, with a socket connected to the other side of the contactor (normally open configuration)?

 

[Prizen]

And then there's the startup load. That's a risk.
Some sort of timer builtin adds to the cost and makes the auto switch from Toolvation a lot more attractive

 

[AndrewG]

I've been experimenting with another approach using a pair of 'smart plugs' like these

Whilst designed to link to your WiFi, they can communicate directly with each other, have built in power monitoring and cost less than £10.

One I have clearly marked 'Slave' and lives on the lead of my Henry vac. The other ' Master' unit usually lives in the socket by my bench where I plug any power tool in. The Master plug is programmed always on, plus a rule that when current detected above a threshold, it sends a message to the slave plug to turn it on. When the current detected fall below another threshold, after a delay it sends a message to the Slave to turn off. Simple.

Well like all new tech, not quite. I am using open source firmware called Tasmota, that must be flashed over the manufacturer's code.

I'm interested in what others think. I could write a fuller How-to, but this might be too geeky for real woodworkers.

 

[Prizen]

I've been experimenting with another approach using a pair of 'smart plugs' like these

Whilst designed to link to your WiFi, they can communicate directly with each other, have built in power monitoring and cost less than £10.

One I have clearly marked 'Slave' and lives on the lead of my Henry vac. The other ' Master' unit usually lives in the socket by my bench where I plug any power tool in. The Master plug is programmed always on, plus a rule that when current detected above a threshold, it sends a message to the slave plug to turn it on. When the current detected fall below another threshold, after a delay it sends a message to the Slave to turn off. Simple.

Well like all new tech, not quite. I am using open source firmware called Tasmota, that must be flashed over the manufacturer's code.

I'm interested in what others think. I could write a fuller How-to, but this might be too geeky for real woodworkers.

I am very much interested in this Andrew! We really appreciate any advice!

 

[Yojevol]

I'm interested in what others think. I could write a fuller How-to, but this might be too geeky for real woodworkers.

What about us real geeky wordworkers?
Yes Please

 

[Alex]

Maybe keep it simple and get remote socket like a lot of us use. Velcro band round wrist and bit velcro on back remote attaches it to your wrist. Tap remote to fire vacuum before start the tablesaw and tap off on remote after tablesaw switches off. Works brilliant. Like this one on ebay.
https://www.ebay.co.uk/itm/MasterPlug-P ... SwgqZd9Rt6

Edit: Sorry see someones already said use remote plug. Just to add I have festool vacs and other vacs with power sensing plugs for site use, a in the workshop use remote plug with built in standard vacuum atttached to cyclone separator.

 

[AndrewG]

Ok so for the geeky woodworkers I'll try and recall the information and get something posted over the weekend.

Andrew

 

[AndrewG]

OK, so I stumbled across this possibility when investigating home automation. I have been trying things out in my workshop as I am interested in seeing how practical the low cost solutions now are. The new generation of remote control plugs use home wifi to connect, making integration with services like Amazon Alexa easier Whilst ease of use is often achieved by devices communicating back to the manufacturers servers, I wanted everything controlled locally with no link to the internet (I wear a tin foil hat). This meant going with an Open Source solutions.

CAVEAT EMPTOR

I describe below how I have done it - there might be alternative/easier ways. To do it this way you need wireless in your workshop, a smart phone and a raspberry pi (to flash new software). It does not work outside my workshop as the plugs must be on a network with IP addresses.

Tasmota is alternative open source firmware for these wifi plugs that is easy to use and very well supported. There is an excellent site that tracks which devices are compatible with this solution at https://templates.blakadder.com/. Having checked I bought two plugs for £16 from Amazon.

The main hurdle is replacing the plug’s manufacturer’s firmware with Tasmota. I managed this easily by following the instructions video here (https://www.youtube.com/watch?v=dyUyewiKpRA) Warning - Raspberry Pi required, but no soldering

Once you have set up your plugs with Tasmota on your wifi home network, they can become part of a larger home automation system (I am using another Open Source solution ‘Home Assistant’ running on a cheap Raspberry Pi as a home automation server). However the Tasmota firmware also allows each plug to run its own rules AND communicate with each other.

A little reading of the documentation here( https://github.com/arendst/Tasmota/wiki/Rule-cookbook ) provided me with this solution

Enter these line into the ‘CONSOLE’ UI of MASTER plug

Rule1 on ENERGY#Current>0.100 do Websend [<SlaveIP>] power 1 endon on ENERGY#Current<0.100 do Backlog delay 10; WebSend [<SlaveIP>] power 0 endon

ENTER

Rule 5

ENTER

Rule1 1

ENTER

Now when the Master plug detects a current through it over 0.1A, it sends a message to the Slave Plug to turn on. When the current drops below 0.1A, after a delay it turns the Slave plug off. The ‘Rule 5’ is to make the message only sent when it first changes. Rule1 1 turns your rule on

Clearly this is for the confident geek only, but I would be interested if those more technical than I can take this further and make it more robust. I think home automation has a lot of applications for the workshop.