Turn on a device with either of 2 others are turned on.

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  #1  
Old 01-25-13, 10:22 PM
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Turn on a device with either of 2 others are turned on.

I have 2 devices (table saw and router) which each are controlled by a switch which also turns on an outlet that is mounted to the frame of each tool. That outlet is used to turn on the shop vac. It requires moving the cord for the shop vac from one to the other and back every time.

I want to wire it up so that the shop vac is plugged into another outlet that is energized whenever either of the other two are turned on. I am trying to encorporate this into a blast gate configuration so that i can move one lever and change both suction and the power to the vac in one motion.

I'm considering relays, or a 3-way switch to select one or the other, or ????

I want to prevent back feeding from one to the other to prevent both tools coming on whenever one is started. Both tools are connected to the same circuit so there isn't a risk of feeding between two circuits.

Any ideas?
 
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  #2  
Old 01-26-13, 05:05 AM
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Welcome to the forums.

I would do two SPST relays with the normally open contacts paralleled on the hot side of the outlet that powers the vac. Coils are powered by the power tools' switches.

Mount the relays in a box with a receptacle, and use S-rated cables for the plugs that will connect to the tools.
 
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Old 01-26-13, 05:06 AM
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Welcome to the forums! I can save you a lot or miscellaneous wiring that you will trip over eventually. I use one of these. The remote control has a magnet on the back so you can either put it in your pocket or stick it to the side of the tool. You can also buy an additional remote if your shop is too big, or you only have a couple of tools to operate. Plug your dust collection system into the wall box, and everytime you turn on a machine, just point and shoot. DUST COLLECTOR REMOTE CONTROL SWITCH - 110V By Peachtree Woodworking - PW466 - Amazon.com
 
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Old 01-26-13, 05:14 AM
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Sounds like you need a current transformer relay with a current transformer on each tool. That way the dust collector would start automatically when each tool starts.
 
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Old 01-26-13, 05:53 AM
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Both tools would need to be relay isolated. You can't get away with one relay. The transformer power from the activated tool would backfeed into the secondary of the tool that is off.. That would create a step-up situation, and bad things would ensue.

As Rick already mentioned, two relays (or three with a transformer if you want a low-voltage interconnect) is the way to go.
 
  #6  
Old 01-26-13, 07:09 AM
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Thanks for the quick responses.

Rick, I am unfamiliar with S-rated cable. Can you give a short description? I was thinking of using either 14-3 or 12-3 cable ( that I have) with a male plug at the tool end and hard wired in a box mounted to the blast gate manifold mounted at the ceiling of the shop. Ceiling is unfinished so the manifold will just be screwed to an open floor joist. The cables would be routed vertically from each tool, roughly following the vacuum hoses so that there is a reduced tripping risk. Relays would be 120v coils.

Chandler, I have seen that remote at the local woodworkers guild. It works well. There is a similar one via the local Woodcraft store. I have considered them and am trying to do this on the cheap. That said they are an attractive solution.

Buy 110V Remote at Woodcraft
 
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Old 01-26-13, 07:29 AM
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S rated cable = SO type cord (SJO, SOOW, etc)

There are a couple of ways to do this, as you can see. Here is a couple of other options:

You could install 3 way and 4 way switches in locations that will control the receptacle(s) that operate the vac. Just put a switch at each machine.

Install some blast gates with low voltage switches. Connect the switches to a relay with a 24 volt coil that controls the above mentioned receptacles that run the vac. You would need a low voltage transformer but they are cheap.

Use come central vacuum ports with low voltage connections and run similar to a central vacuum. vacuum.
 
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Old 01-26-13, 07:32 AM
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Ray,

I have looked at current transformers and relays. Most seem to be industrial sized. Can you suggest ones that are appropriate for home shop use?
 

Last edited by ray2047; 01-26-13 at 09:54 AM. Reason: None. Hit wrong button.
  #9  
Old 01-26-13, 09:45 AM
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Can you suggest ones [CT relays] that are appropriate for home shop use
Sorry, I can't. I have never bought any. Tolyn's suggestion of 3&4-way switches would be easy and cheap.
 
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Old 01-26-13, 10:07 AM
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Thanks for the suggestions. It prompted me to spend some time outlining the pros and cons. Here is the whole thought process. The table is too big to post. The short version in order of preference:

1. Use a 3-way switch mounted under the lip of the router table. Resolve the tripping hazard with a cord protector between saw and router. It's only a few feet.
2. Do nothing. I'll just keep replugging it when I need to.
3. Remote control. It has lots of benefits but a hefty cost.
4. Blast Gate activated 3-way switch. It "should work." but requires very precise manifold design and construction.
5. Relays. Extra circuitry seems like a waste of time to solve what is really a laziness problem.
6. Current relays. Ditto.

Thanks for your help.
 
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Old 01-26-13, 11:19 AM
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Just for note, the blast gate idea (#4) you would just need some cheap mirco switches. Install one at each blast gate and wire them in parallel. When you have the a gate open, the switch will trip and the vac will run.

Here is the option I am using now in my shop: Power Maintained Foot Switch
 
  #12  
Old 01-26-13, 07:33 PM
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.


Not sure if your still considering it.....but.....there is a way to control the vac with one relay.

As Rick mentioned....you could simply mount the relay in a box with a receptacle.....and just
use corded plugs to connect to the tools.....allowing the vac to come on automatically.


.
 
  #13  
Old 01-27-13, 05:30 AM
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Halton, I'm interested in learning how it could be done with one relay. Dual coil?
 
  #14  
Old 01-27-13, 08:21 AM
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I'm interested in learning how it could be done with one relay. Dual coil?

Just a regular DPDT relay.....the key is that you only need to activate the coil from one source.

So.....when the table saw is powered....the feed goes through the normally closed path to the common contacts.....which goes to the vacuum. When the router is powered.....that feed uses the normally open contacts.....but....it also feeds the coil....which then closes the contacts to allow the router to feed the vacuum.

This could be done with a simple $7 relay similar to this..... MAGNECRAFT 92S11A22D-120A Relay, Power, 8 Pin, DPDT, 30A, 120VAC - Amazon.com

I had a problem to solve when I was noodling with powering my sump pump with both line feed and a battery back-up power feed.....then it dawned on me to do it this way using one relay.....


.
 
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Old 01-28-13, 08:12 PM
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Halton,

Thanks for the suggestion. This will do exactly what I want and is easy to do.

I have ordered one from Zoro Tools (via Amazon). There are other vendors, but none beat their price.

I assume this can be screwed to the back of a blue electrical box. Being without a crimper, and planning to use solid wire, I assume that flat blade connectors soldered to the terminals will make a sufficient and safe connection. Can you advise it either of those assumptions are wrong?
 
  #16  
Old 01-28-13, 10:47 PM
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Rather than screwing the relay to the back of a plastic box.....it might be better to mount it inside a 4" deep or 4-11/16" deep junction box with a single duplex plate.

In lieu of crimping the terminals on......you can solder them on instead.
If you are quick and careful solderer.....you could solder the wires directly on the terminals.
 
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