DC Wiring Question

[Larry Fox]

I picked up a used cyclone-based DC system and am thinking about installation options and have some questions on wiring it. It came with a contactor with a 115-v normally open solenoid that pulls the contactor in and starts the motor. Previous owner had it wired to a simple switch but it occurs to me that I can get a bit more fancy with it and have it activated whenever I start a connected machine. My plan is to connect one leg of the load side of the switch for each of my 220v machines to energize this solenoid whenver I turn the machine on. I am pretty much a one-machine-running-at-a-time kinda shop. To illustrate my question / concern consider just the jointer and TS. They are both on their own (seperate) circuit. I have one leg of the 220 picked up on the load side of each and running to the solenoid (beinc careful to make sure that I take from the same side of the bus to maintain polarity). If the jointer is off and I turn on the TS, this will energize the solenoid but will also back-feed one leg of the jointer motor. Will this cause a problem. Intuitively, this sounds fishy but I don't know for sure.

I have done nothing with it to tis point so have nothing but options so if you have other suggestions please make them. I know this is fairly common - how do others do it?

Thanks in advance for you time . . .

L

[Jim Becker]

The way it was done in a Fine Woodworking article years ago was to put some kind of current sensing coil on the machine circuits that would provide the trigger. That's way more complicated than I would want to get. I'm having trouble visualizing how the method you describe would actually work, especially given most 240v machine circuits don't have the neutral conductor required for the 120v side of things.

Given you have a contactor with a 120v control side, it may be just plain more practical to wire up a centrally located switch or use a cheap RF remote. (I use the simple switch located smack-dab in the middle of the shop)

[Rob Will]

Larry,
I seriously thought about doing that sort of thing but decided against it. It sounds neat but I think you will be more satisfied in the long term with a series of switches around the shop. You might even use a different color to make them stand out. In my shop, I ended up going with a 24V coil on the starter and installing four separate control stations where I can get to them.

Rob

[Rick Christopherson]

By doing what you suggest, you would be effectively shorting all of your machines together. Among other things, one machine could pull power through all of the circuit breakers, such that a single wire could carry several times its rated capacity without tripping any of the breakers.

It also is generally not a good idea to have a dust collector turn on every time a tool turns on, as this can result in an excessively high duty cycle for the dust collector.

[Bruce Wrenn]

The way it was done in a Fine Woodworking article years ago was to put some kind of current sensing coil on the machine circuits that would provide the trigger. That's way more complicated than I would want to get. I'm having trouble visualizing how the method you describe would actually work, especially given most 240v machine circuits don't have the neutral conductor required for the 120v side of things.

Given you have a contactor with a 120v control side, it may be just plain more practical to wire up a centrally located switch or use a cheap RF remote. (I use the simple switch located smack-dab in the middle of the shop)

I have the sensor system in my panel box that was in FWW (Aug 2000) I added a cube timer (delay on off) to allow the machine to run 10 extra seconds to clear dust from ductwork. One leg of all the 220 circuits, except welder and air compressor, pass through sensor. It is a true pleasure to not have to keep up with a remote. I once taught shop in a school. Shop was about 5000 square feet. It only had one place to operate DC. Needless to say it wasn't turned on regularly.

[Mike Heidrick]

I would get a $10 outdoor remote from Menards or Wally World and use it with the 110V relay.

[Larry Fox]

thanks everyone - I knew it sounded fishy - just didn't know why. Jim, I will take a look at the FWW article.