A
Anonymous
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I’ve followed the recent thread on “semi-automatic switching for d/c systems”; some of you might be interested in the solution I’ve come out with. I’ve done quite a lot of reading on this; US w/workers tend to opt for an infra-red manual switch, but I wanted something truly automatic, which led me to: (a) vibration sensors mounted on each machine; (b) using mechanical l/v switches built into blast gates, or; (c) current sensing.
On (c), I got as far as reading about Hall effect sensors but my knowledge of electronics is not good enough to design such a circuit, and I never found a ready-made circuit diagram. The answer I found came from Maplin, who sell something called a “master/slave power controller module” (http://www.maplin.co.uk/, product code N74AU). This switches on the “slave” (the d/c in this case) when the “master” machine draws current. The master can be up to 4kw, and the slave can draw up to 10A according to the spec (it can cope with 3-phase as well as single, it says).
I fitted a second ring main in my workshop with distinctive sockets (metal clad, versus white plastic for my first, existing ring) which is solely for the machines to be d/c connected. Wiring the live conductor of this second ring through the master side of the controller module means that any time a machine on this ring draws current, the slave d/c (which is powered from a socket on the first ring) comes on. For extra versatility, the d/c power is controlled by a 3-way switch so that it’s either off, on for the automatic master/ slave circuit, or a “manual override” on position so that I can hoover up loose dust at the end of the day.
I would just mention that I stumbled across this site thanks to a passing reference in the Google uk d-i-y discussion group. It's absolutely fantastic to find a UK group that has a critical mass of knowledgeable contributors; I've spent years reading the likes of The WWA Info Exchange (fantastically enthusiastic contributors, but v. galling to see such HUGE shops and such CHEAP tools) and Taunton's "Knots".
John Forbes
On (c), I got as far as reading about Hall effect sensors but my knowledge of electronics is not good enough to design such a circuit, and I never found a ready-made circuit diagram. The answer I found came from Maplin, who sell something called a “master/slave power controller module” (http://www.maplin.co.uk/, product code N74AU). This switches on the “slave” (the d/c in this case) when the “master” machine draws current. The master can be up to 4kw, and the slave can draw up to 10A according to the spec (it can cope with 3-phase as well as single, it says).
I fitted a second ring main in my workshop with distinctive sockets (metal clad, versus white plastic for my first, existing ring) which is solely for the machines to be d/c connected. Wiring the live conductor of this second ring through the master side of the controller module means that any time a machine on this ring draws current, the slave d/c (which is powered from a socket on the first ring) comes on. For extra versatility, the d/c power is controlled by a 3-way switch so that it’s either off, on for the automatic master/ slave circuit, or a “manual override” on position so that I can hoover up loose dust at the end of the day.
I would just mention that I stumbled across this site thanks to a passing reference in the Google uk d-i-y discussion group. It's absolutely fantastic to find a UK group that has a critical mass of knowledgeable contributors; I've spent years reading the likes of The WWA Info Exchange (fantastically enthusiastic contributors, but v. galling to see such HUGE shops and such CHEAP tools) and Taunton's "Knots".
John Forbes
