Can any one advise me where I can find a circuit diagram for the power take off sockets as fitted to some vacuum cleaners, so that they switch on automatically when a power tool plugged in to the PTO socket is switched on? I would like to build a unit to fit to an existing vacuum cleaner used as a dust extractor for a circular saw, rather than buy a new vacuum cleaner with power take off built in.
snipped-for-privacy@hotmail.com wrote: > Can any one advise me where I can find a circuit diagram for the power > take off sockets as fitted to some vacuum cleaners, so that they switch > on automatically when a power tool plugged in to the PTO socket is > switched on? I would like to build a unit to fit to an existing vacuum > cleaner used as a dust extractor for a circular saw, rather than buy a > new vacuum cleaner with power take off built in.
So what you really want is for the vac to turn on when the saw comes on? Something like this?
I doubt the PTO socket on the vacuum is intended for a load like the saw. If it was, wouln't it just have an Edison socket to plug in the controlling device rather than a proprietary socket?
GG
That circuit is not suitable for the application. It introduces a voltage drop to the saw, which is something you do not want.
Better off to use a toroidal current transformer, and a different circuit, or buy a pre-made unit.
I made my own, by modifying a GFCI receptacle circuit. These are the steps that need to be taken: You need to replace the solenoid from the GFCI with a 2.2K resistor, and wire the GFCI in the circuit such that it will trip when the saw is turned on. (Wire the hot wire to the line side, and the neutral wire to the load side. The saw plugs in to the receptacle.)
Normally, the solenoid is activated by an SCR in the GFCI. With the modification you take the output of the SCR to a 4.7uF
250V filter cap through a 1K resistor. (The other side of the cap is grounded.) From cap + , through 3.2K to an optoisolator (I used an MOC3031, and I also put a LED in series as an indicator) to ground.The output of the optoisolator drives a standard triac circuit, which can be used to operate a 110 vac relay. There are at least two different GFCI circuits used in GFCI receptacles - the one I modified uses the LM1851 chip.
In my case, I did not use the CT that is built in to the GFCI, as I was putting the circuit into a smaller space, and not using the GFCI receptacle - just the circuit.
I can post a jpeg on abse if anyone wants it.
Ed
Why not just run them both off one switch. Get an outlet box, and a switch that's rated for the total startup current of both simultaneously, and a duplex outlet. Plug the saw and vacuum into the duplex outlet, and leave their switches on. Be sure that it's fused sufficiently, too.
Have Fun! Rich
The whole idea, was to be able to connect several appliances to one power circuit running through the PTO so that when any of the appliances was switched on, the vacuum cleaner/dust extractor would automatically switch on too. I realise that only one appliance could be run at any time with the vacuum cleaner as the power supply to the workshop is only rated at max 3200w (230v UK supply)
Max rated output of PTO on the machine I have looked at is 1800w which with the 1000w of the vacuum cleaner, just leaves enough reserve for the workshop lights, as the total power supply to the workshop is
3200w.Thanks for your reply.
First class reply, many thanks, I hope to construct this circuit during the next few weeks.
Oh, then a current transformer at the input end of a power strip, and the logic for it. :-)
Good Luck! Rich
practical for a bench saw or panel saw, but perhaps a little inconvenent for a drop saw or a hand-held circular saw (which are typically switched bya a trigger in the handle.
Bye. Jasen
snipped-for-privacy@hotmail.com wrote in news:1147040347.333834.71890 @j33g2000cwa.googlegroups.com:
I did this for the table saw in my shop. The sense section was a homebrew current transformer made from a 110vac-24vac, E-I core, parallel bobbin transformer with the secondary removed and replaced with a few turns of the hot wire from the table saw circuit. On the vacuum side I did a delay-on-ON so the saw and vacuum didn't start similtaniously (very high current draw). Also, a delay-on-OFF circuit so that the vacuum continued for a several seconds after the saw was shut off.
The circuit diagram is on my computer at work, so I'll pull it off tomorrow and post it.
Ken
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