current sensing relay

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e57

e57

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San Francisco, CA
Looking to make some major improvements to the ventilation and dust collection in my garage/wood/welding/shop/dance floor down stairs. What I want to do is put in a small panel that I can do two things with.
  1. Lock OFF - because I have a little one who will be getting old enough to turn something on some day.
  2. If any of those things on that panel go ON - I want to start the vac/blower/negative air automaticly, and stay on for roughly tem minutes after whatever I use is off.
#2 is the one I need help with.... If the welder is on it needs to get vented - and like wise if the saw or router are on - it needs to get vacuumed.... There are a number of vacuums that do this - whatever you have plugged into the 15R on the unit turns on the vacuum. But my table saw and that same vacuum are over 20A together, and likewise I can not plug my 240 welder into it either.... There are some remote controlled vacuum switches out there, but I often misplace my coffee down there and spend ten minutes freaking out trying to find it - I need something full auto....

Any ideas?
 
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Universal AC Current Sensor, Input Line Voltage 120 VAC, Maximum Output Current @ 240 VAC 10 Amps, Maximum Inrush Current 300 Amps, Mounting Surface, SPDT
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AC Current Sensor

Of course you would still need an off delay and a contactor to kill the branches or feeder etc.
 
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e57,

I have designed and built a widget that does exactly what you are describing for item #2. I too am a wood worker and wanted an automatic control to start my dust collection system when a shop tool was turned on. The widget I built has on/off/auto switch for convenience. It can handle up to a 30A dust collector and a maximum tool current of 100A. I built one for a buddy with a cabinet shop and he loves it! I have an extra prototype if you are interested.........
 
jimday said:
e57,

I have designed and built a widget that does exactly what you are describing for item #2. I too am a wood worker and wanted an automatic control to start my dust collection system when a shop tool was turned on. The widget I built has on/off/auto switch for convenience. It can handle up to a 30A dust collector and a maximum tool current of 100A. I built one for a buddy with a cabinet shop and he loves it! I have an extra prototype if you are interested.........
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Yes - I am! Drop me a PM.... I too was thinking of widgetizing the final solution, because I have no idea why there is not some off-the shelf package sold at Woodcraft for just this application* - and I am sure you are well aware of who people hobby it up with wood love to spend money!

Well there is - but not at a capacity useful to most hobby or pro level shops.... My saw draws >13a ripping long heavy mahogany - my small vac is 7.5.....
 
I did building automation mostly carrier for many years and one of thier motor logic pieces was a ct and not an aux contact because it would more truly represent a running motor than an aux contact in a starter. United Technologies is the parent company. I suggest one of these dry contact relays to a starter for what you wish to accomplish. edit to say I just looked at the one Bob posted and it looks perfect for the price of under a hundred bucks.
 
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quogueelectric said:
edit to say I just looked at the one Bob posted and it looks perfect for the price of under a hundred bucks.
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Try closer - well - above $200.... 2 current sensors, and a timer/contactor for the vac/blower. The blower and vac will exceed the contact ratings of the sensor, and need to stay on for a bit after each operation.

The lock off part of this - item #1 could just be a disco with a LOTO tag that says "You're gonna be be in deep trouble little one!" - but will probably toss the actual lock on for good measure.

What I want is a small >60A say 8/16 panel then a few 120 circuits out of that, and a 50a 240 MIG welder. If any of the 120's are turned on - the fan starts. If the welder is on - the fan starts.... I could do it with just one current sensor on one leg - but would be limited to operation on only one leg for the 120 stuff. Which may be a cost saver, as I can have the power for the vac/blower come from the other, as most of the time it would only be one tool, and the vac at a time.... Hmmmmm.... :rolleyes:
 
The home depot guys have a keypunch systen to operate all of thier equipment NOW THAT IS TOTALLY TESTED EVERY DAY AND IDIOTPROOF and clever childproof this looks like what you need. Did I say Idiotproof tested daily oh yeah I did. Edit to say I have 2 little ones with horns holding up the halo a 2 yr old in diapers and I am almost 50.
 
e57 said:
Yes - I am! Drop me a PM.... I too was thinking of widgetizing the final solution, because I have no idea why there is not some off-the shelf package sold at Woodcraft for just this application* - and I am sure you are well aware of who people hobby it up with wood love to spend money!

Well there is - but not at a capacity useful to most hobby or pro level shops.... My saw draws >13a ripping long heavy mahogany - my small vac is 7.5.....
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It killed me to watch my cabinetry friend build a 60,000 gazebo out of mahogany only to paint it white. I am still getting chest pains from that one. God bless the rich and famous.
 
quogueelectric said:
It killed me to watch my cabinetry friend build a 60,000 gazebo out of mahogany only to paint it white.
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Yes a waste of trees - and money. This bassinet is my last little project I made for my sister who is due in July. Back on topic the the runners between the legs were close to stalling the saw at full depth of cut, so I could not use the vac & blower at same time during those cuts - had dust blowing all over the house - wife not happy. You would figure that I would be smart enough to run a cord over to a different circuit.... Guess the drone of a vacuum on the whole time setting up those cuts would have drove me nuts on second thought....
 
080529-0633 EST

e57:

One current transformer. One hot wire goes thru in one direction, and the other in the opposite direction. This way the opposite phases do not cancel when both are on at the same time.

A threshold detector, an off delay timer, and an adequate relay for the vacuum.

There are some Hall device current sensors that require some DC excitation and provide a voltage output. Combine one or two of these with an op-amp, maybe a simple microprocessor, and the power relay.

If iwire's device has a large enough hole in the current transformer for your two hot wires it will work. Use its output to pilot a power relay for the vacuum. Maybe make an external current transformer, 1 to 1 ratio, with a big enough hole that then feeds this device.

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