Current activated switch

[m8]

Need to switch on my extractor fans/hoover any time any of the workshop tools are turned on Router table saw chop saw. Has anyone had any experience with this type of current switch Please

Mike

[Seekonk]

Common solution is a go/nogo self powered relay.  These are usually 10A with a toroid you place the sense wire through.  Don't have 10A, just pass multiple loops through the coil.  Most motors have a high current surge so even 3A easily pulls in a relay.   Trouble is you usually need a timer relay so the fan operates for a minimum of 5 minutes so you aren't short cycling the fan all the time.

[m8]

That's what we used to use but cant find a source of them in 110v/240V at the moment - as to the timer that's easy have those available already but unfortunately need to find them in 110V now to do the same job

[Seekonk]

Here is one of the self powered relays I was talking about that requires no power connection.  This can then be used to switch on a timer relay.  They also offer powered versions that have a timer built in.

www.rke.com/item/ac-current-relays/go-no-go-ac-current-sensing-relay/mcdr?

[MLXXXp]

Maybe you could use one of those "smart" power bars that have a built in current activated switch. When current is drawn from the "master" outlet, other outlets are switched on.
E.g. http://www.smarthomeusa.com/smart-strip-power-strip-automatic-switching-surge-suppressor/

[SeanB]

Current sense relay, or a simple series resistor with a thermal switch attached to it, so that when it gets hot it turns on the output. Put a non resettable thermal fuse in series with the supply for safety, and if you use a ceramic cased resistor on a heat resistant ( mica sheet with high temperature terminals on it, and all connections crimped or screw connectors) base you can use a 200C safety fuse, and a 80C NO resettable Clixon as the output switch.

[m8]

Smart Power bars not an option - I need to switch 20A using a contator and timed off as well. As to the thermal option - I might as well monitor the voltage drop across the resistor or even put an opticla Isolator in parallel with diode limiters. Another problem is  Im in the UK and most of the options commented on are only available in the states and Ive inquired from RKE do they supply here. And the answer is no. Im trying other options at the momement - Thanks so far will keep listening

Mike
GD6ICR