Thread: Current sense switch - For dust extraction automation

I have installed an automatic dust extraction system in my shed with automatic blast gates, etc and one of the things I needed was a way to sense when things like the pedestal drill, SCMS and other plug in 240V items are running.

I came across this website which goes into detail about a current sense slave switch -Current Sensing Slave Power Switch
Perfect for my application.

As the majority of my workshop items that I want to use this on have motors, the high current version was required.

So I draw the circuit up in Eagle CAD (Larger & clearer imaged attached at bottom of post)



And then did the PCB layout



This one is the SMD package version. I will upload the through hole version a bit later (needs a tidy up).
Parts list for through hole is below and attached as an Excel spreadsheet.

Please note - The resistors have been valued for a 24VDC system as the PLC's I use have 24VDC inputs. I am sure it would work with other voltages but resistor values may need adjusting.

I have put part numbers from Element14 - They are certainly not the cheapest, but certainly the easiest to link to give an idea of attributes of the parts required.




I get my printed circuit boards manufactured by Itead Studio in China. One-stop Online Service For PCB Board Design Manufacture And Arduino Development Module Shield
For a 5cm x 5cm board like this is ~ $12.50AU plus shipping, for 10 boards at around at 2-3 week delivery time. The Gerber files required to have these boards made is at the bottom of this post. Edit - ZIP file for through hole boards attached

If anyone is interested in the SMD Gerber files, let me know and I will upload them also.

Got these installed in my workshop and the FIL's, all working as intended.





Once they are soldered up, I connect 24VDC supply and switch wire back to the controller. Then the active on the power point to my machine gets looped through the current transformer and then mount it in an adaptable box. These could be done in a junction box beside the power point, or even done on the flexible cable from your machine - If you know what you are doing.
Only the active or the neutral should loop through the current transformer. Not both. The circuit board should not be installed anywhere that 240VAC terminations exist.

All electrical works on mains cabling should always be done by a qualified electrician.


First prototype show in the pic below.