Building an automatic switch with timer overrun?

[Huey]

Hi all, I am new here and am looking for some advice . . . .

I would like to build a device that does extactly what this one from the USA does -

**broken link removed**

that is, when a device plugged into one scoket is switched on another socket is powered on and that second socket stays live for a couple of seconds after the main device plugged into main socket is switched off.

can anyone tell me how this device works, and what compnents I would need to build one?

many thanks!

Huey

 

[tcmtech]

If you have an old GFI device you can hack the circuit on it to work as a sensing and relay triggering device. You only use one line instead to the two that goes through the sensing coil then use the small DC output that normally triggered the trip coil to drive a continuous duty relay.

Or at least thats how it could be done with the old GFI units.

 

[KMoffett]

Mine is in here: https://forum.allaboutcircuits.com/showpost.php?p=58447&postcount=6

Seems like the commercial ones started popping up after I posted it.

Ken

 

[Huey]

Hi Ken, thanks! yours is exactly the same application I want to make this for! I have a cheap shop vac that I use to extract dust from my mitre saw / router etc - currently I turn it on manually - which gets pretty tiresome . . . a festool or similar extractor is too expensive for the amount I use it, plus i would like to learn something along the way. . . . .

Do you have any photos of your unit? I am a complete novice and am just learning what the symbols on your circuit diagram represent!

thanks again

Huey

 

[KMoffett]

Huey,

Mine is on a table saw at work and I'm off today, but can take a picture tomorrow. You may or may not have noticed that some things are left off the schematics. When I posted those, it was just to get the concept and basic circuit out there. I'll see if I can put together a more complete schematic.

Ken

 

[Huey]

thanks Ken, that would be a great help.

Huey

 

[KMoffett]

Sorry about the mixed order.

1st photo: Current transformer in saw start control.
2nd photo: Inside saw-start control box.
3rd photo: Shopvac delay schematic.
4th photo: Inside Shopvac delay box
5th photo: Saw-start control schematic.
6th photo: Shopvac delay box.
7th photo: Saw-start control box.

Ken