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post #1 of 35 (permalink) Old 10-04-2013, 09:27 AM Thread Starter
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For quite some time I've been searching EBay for master/slave switches that enable the dust collector to switch on with the saw/router/lathe etc but without success. I was surprised and pleased a couple of weeks ago when the daily EBay suggestion email arrived and low and behold there were the exact type of switch from Germany at just under $20.00 each. The three that I ordered arrived yesterday and today I made a box and connected it all up. Well, imagine my surprise when I switched on the main power and the dust collector started up (the Bosch glide saw wasn't switched on). I did some quick checks but all seemed OK so I connected my table saw and it's dust collector and this worked perfectly. It was obvious that the Bosch saw was drawing current even when it and it's twin laser beams were in the off position. My next test was to check across the live and neutral pins of the power plug and there was a reading of 14.3Kohms, which, to say the least was surprising. I drove to the store from whence it came and surprise, surprise, their display one checked the same. My conclusion is that the power supply for the laser beams is poorly designed in as much as the low voltage must be switched instead of the mains, hence a small transformer is drawing sufficient current to operate the master/slave switch.
I shall be phoning Bosch on Monday and I'll let you know the result.
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post #2 of 35 (permalink) Old 10-04-2013, 11:29 AM
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Which means it is costing you money even when you are not running it. Immediate quick fix is to unplug it when not in use.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
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post #3 of 35 (permalink) Old 10-04-2013, 12:04 PM
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You beat me to it, Charles.
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post #4 of 35 (permalink) Old 10-05-2013, 07:48 AM
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Quote:
Originally Posted by harrysin View Post
For quite some time I've been searching EBay for master/slave switches that enable the dust collector to switch on with the saw/router/lathe etc but without success. I was surprised and pleased a couple of weeks ago when the daily EBay suggestion email arrived and low and behold there were the exact type of switch from Germany at just under $20.00 each. The three that I ordered arrived yesterday and today I made a box and connected it all up. Well, imagine my surprise when I switched on the main power and the dust collector started up (the Bosch glide saw wasn't switched on). I did some quick checks but all seemed OK so I connected my table saw and it's dust collector and this worked perfectly. It was obvious that the Bosch saw was drawing current even when it and it's twin laser beams were in the off position. My next test was to check across the live and neutral pins of the power plug and there was a reading of 14.3Kohms, which, to say the least was surprising. I drove to the store from whence it came and surprise, surprise, their display one checked the same. My conclusion is that the power supply for the laser beams is poorly designed in as much as the low voltage must be switched instead of the mains, hence a small transformer is drawing sufficient current to operate the master/slave switch.
I shall be phoning Bosch on Monday and I'll let you know the result.
I would be more inclined to phone Kemo or their rep. 14.3K at 230V (in DC terms) is only 3.7Watts, which is pretty darn low and would probably be higher for a built in viewing light. My GMC miter saw also has twin lasers and although the handle gets slightly warm on standby (that's where the transformer is) it doesn't set off either of my master/slave switches which are built into the two shop vacs.
ISTM that Kemo have not factored this in and the trip current is set far too low.

It's also worth noting that the entire Kemo website is down, not even acknowledged as existent, which makes me wonder if they are out of business and someone is selling off stock, perhaps sub-standard?

Regards,

Alan.
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post #5 of 35 (permalink) Old 10-05-2013, 09:47 AM
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Oh, the time a retired man has on his hands...
Love ya, Harry

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post #6 of 35 (permalink) Old 10-05-2013, 10:12 AM Thread Starter
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Charles & Dan, the point is not that it's costing in electricity but the fact that I can't use it with the master/slave switch.

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post #7 of 35 (permalink) Old 10-05-2013, 10:25 AM Thread Starter
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Alan, the rating is that it will switch at 6watts. My disappointment is that I never considered that anyone would switch the DC output rather than the AC mains input.

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post #8 of 35 (permalink) Old 10-05-2013, 10:26 AM Thread Starter
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Oh, the time a retired man has on his hands...
Love ya, Harry
Believe me Barb., the days aren't long enough to fit in all that I have to do.

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post #9 of 35 (permalink) Old 10-05-2013, 11:13 AM
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Alan, the rating is that it will switch at 6watts. My disappointment is that I never considered that anyone would switch the DC output rather than the AC mains input.
Harry, I know we're talking in terms of AC and it's really impedance that counts, but DC values should suffice.

14.3K @ 230V = 3.7W (approx) which is sufficiently under your quoted 6W figure, so IMO the device is out of spec or needs adjusting.

It's not unusual to switch the low voltage (DC) side of many devices these days. Very often the 'OFF' switch only kills the output, not the supply. It allows the manufacturer to skip round heavy safety insulation for high voltage devices, making the overall cost (to them) cheaper!

I realize that you're not too worried about the small current consumption, but the inconvenience of not being able to use the master/slave device really is an issue and the supplier of the device should correct it.

Personally, I'd demand a refund on an out-of-spec device, then go look round the thrift stores/garage sales or perhaps one of the online freecycle schemes, for an old shop vac with an AC outlet. They're often discarded because the armatures or bearings have failed, leaving a useable master/slave switch. You could probably get a beaten up device for not far off $5.
You don't need to be an electrical genius to work out where the power goes in and comes out and connect it according to your needs.
The only issue for you would be finding a 230V device, which I guess would be more rare in the USA?

Regards,

Alan.
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post #10 of 35 (permalink) Old 10-05-2013, 12:27 PM
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Could you rewire the laser transformer on the trigger side so that it wouldn't energize until the saw is spinning? Having the lasers come on after the blade starts turning might be a bit of a nuisance at first but it is something a person could probably learn to deal with.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.

Last edited by Cherryville Chuck; 10-05-2013 at 02:31 PM.
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