Power Take Off Socket

[Lonsdale73]

I have all the bits ordered. I was going to go for the Kemo module, but they wanted £20 for shipping!! I'm back to the original circuit. If the current sensing works, the design can be modified to switch 16A, The current sense transformer has a limit of 20A. It doesn't arrive until late Feb. I am happy to share all the info, but better waiting until I make sure it works reliably.

£18.49 + 8.90 p+p on amazon

 

[Sandyn]

Typical Amazon, they only let you see what they want you to see. First time I clicked on the link I could see it, then next time it was another more expensive seller. I had to select the 'New From' link to see it again. This module is a much easier option.

 

[Lonsdale73]

Had a hunt around the forum and found these I'll use one of those, much easier. No point reinventing the wheel

 

[Sandyn]

I'm committed to building the circuit now. Have all the parts on order. The module is a simpler solution.

 

[Lonsdale73]

I'm committed to building the circuit now. Have all the parts on order. The module is a simpler solution.

Yes, even to my ignorant eye it looks a simple enough arrangement. If I'm understanding it correctly, the double-gang socket is wired to the Master L&N , single gang to the Slave L&N and the Fuse L&N conects to the mains. Thus, anything connected to the double-gang will automatically activate anything connected to the single-gang?

 

[Sandyn]

Here is the manual for the Kemo M103N. In that video, the slave goes to the single socket, used for the dust extraction and the double socket goes to two power tools, but you could have more sockets on each as long as you stay within the maximum current limit 15A, 3600W.
My unit will handle up to 20A (assuming it works) but I will probably design for 16A and have a 16A circuit breaker in the final version.
Would be wise to fit the module in a a fireproof enclosure.

 

[Sandyn]

Kemo make some really good modules. They seem to be the German version of Velleman.

 

[Myfordman]

I did a write up of one I designed and prototyped here TheWoodHaven2 • View topic - Current sensing switch module

 

[Sandyn]

I did a write up of one I designed and prototyped here

Cool. That's using the 'Chinese unit'. Has it continued to work OK? I thought it might be susceptible to nuisance switching . Not that that would be a real problem.
My thinking:- the internal switching circuit has no power apart from the induced power from the current transformer switching a FET probably, so everything inside is high impedance.
If they tested it for susceptibility in EMC, they would have left the output isolated , so no problem. As soon as it's referenced to an external circuit, then the FET may switch on when it is in an RF field, perhaps when you make a phone call....wait...that's a cool feature!!! add it to the documentation

 

[Myfordman]

Cool. That's using the 'Chinese unit'. Has it continued to work OK? I thought it might be susceptible to nuisance switching . Not that that would be a real problem.
My thinking:- the internal switching circuit has no power apart from the induced power from the current transformer switching a FET probably, so everything inside is high impedance.
If they tested it for susceptibility in EMC, they would have left the output isolated , so no problem. As soon as it's referenced to an external circuit, then the FET may switch on when it is in an RF field, perhaps when you make a phone call....wait...that's a cool feature!!! add it to the documentation

Not noticed any issues during the evaluation and I was using the weller soldering iron that is well known for putting out broadband RFI as it switches on and off. Firstly the sensor is not an RF related device as it uses a current transformer and secondly not latching so not like the remote controlled sockets. The added contactor would need powering for more than the odd cycle to pull in and cause any issue.

 

[Sandyn]

doesn't need to be a RF circuit, but what can happen is a bit of track inside the module acts as an receive antenna and you hit a certain narrowband high frequency with an RF source and it induces a voltage in the circuit, causing some problem, but it's fairly rare these days.
That's good that it seems to work as expected another design option and cheap.

 

[OldWood]

I have all the bits ordered. I was going to go for the Kemo module, but they wanted £20 for shipping!! I'm back to the original circuit. If the current sensing works, the design can be modified to switch 16A, The current sense transformer has a limit of 20A. It doesn't arrive until late Feb. I am happy to share all the info, but better waiting until I make sure it works reliably.

Sandyn - I haven't checked the internet but if you have enough technical knowledge to build this device, then have you thought of having a look to make your own current sensing device. It is after all just a coil that sits round the line wire. I can't remember why I made one some years ago, and currently (!!) I don't know where it is but I've come across it in some workshop box since then.

 

[Sandyn]

then have you thought of having a look to make your own current sensing device

Thanks, I have thought of what other ways there might be rather than a current sensing transformer, but it's the simplest. I couldn't wind one, it's small and needs 2000 turns to get enough signal for the other parts. It will use a toroidal core, so almost impossible to hand wind something that small. That would try my patience too much. I think it was just over £5 from Amazon. I'm assuming it's small...If it's the size of a brick I'm stuffed!!