remote-Relay for DC

**dlminehart** · 03-24-2006, 07:26 PM

I'd like the info, Loring. I'm one of those making do with a patched Ace Hdwr switch, but suspect it won't last long.

**bigfoot15** · 03-24-2006, 08:46 PM

absolutely!!
I bought the SHOP FOX switch. Haven't used it much, but suspect it will burn out after awhile.

**preamble** · 03-24-2006, 08:59 PM

I too bought a realy (20amp I think) from the Internet. I was able to fit the relay directly in the switch box of my Delta AP400 DC.
I drilled a hole through the sheetmetal case, installed a grommet, and connected it to a 12vdc low voltage AC to DC adapter which is wired in parallel to normally closed magnetic security alarm switches that I connected to each blast gate.
All that's needed to turn on the DC is to open any blast gate on the system.

Works like a million bucks.
The best part of this over the key fob remote controll untils is that only two actions are required: open the blast gate (which turns on the DC) and turn on the saw.

I have my BT3100, Delta 14" bandsaw, Delta chop saw, Rockler router table, Delta thickness planer, Powermatic jointer, and a floor sweep all connected via 4" thin-wall pvc and Rockler 4" flex tubing.

I never have a problem with draw and have about 35' of tubing in all.

I did have a problem with the inlet of the DC jamming up when using the thickness planer (which is also the furthest piece of equipment away from the DC. I found the culprit to be the x shaped sheet metal gaurd on the intake of the DC. Using a pair of pliers I quickly eliminated that problem!

I'll post some pictures when I get a chance.

**Bollox** · 03-24-2006, 11:37 PM

I've been meaning to do this for months now, I'm very interested in how you did it Loring.
Mike

**monte** · 03-25-2006, 04:09 AM

Go ahead and post it Loring. I bet a lot of people would like to see it.

**Kristofor** · 03-25-2006, 01:11 PM

Originally posted by LCHIEN

Finished a small project today.

<snip>

Anyone interested, want to see the circuits or relay source?

What a silly question, did you expect that people on this forum wouldn't be interested?

When I was working out of the garage I didn't have a fixed location for everything so I was typically about 1 step from being able to turn on the DC, but now that I've relocated to the basement I was planning to buy one of the remotes but I'd rather build one right.

Thanks!

Kristofor.

**Wood_workur** · 03-25-2006, 08:02 PM

Originally posted by LCHIEN

Finished a small project today.

Some people have tried to use a $10 remote switch to control their DC.
They found that the ratings were insufficient to run the DC and it burned up the switch. I think someone was able to fix that by soldering some new traces on the PCB of the switch, but it really is over the ratings of those switches.
Others bought the $80 remote from Grizzly.

I decided to resolve mine differently. This will also work for those Sears Slave switches used to turn on a Shop Vac, when the Power tool goes on. but you want to operate the shop vac from a separate AC circuit so as to give all 15Amps to the Table saw.

The heart of the device is a $6 relay or contactor I bought on the internet. It will switch 40A resistive or 30Amps motor current and has a 120V coil that takes just 5 watts to pull in the relay. You can control the relay with the remote switch or the slave switch.

Anyone interested, want to see the circuits or relay source?

As long as the non-engineers here can read it!!!

**Stan** · 03-25-2006, 08:20 PM

I'd like to see this setup also.

**lcm1947** · 03-25-2006, 08:43 PM

Yeah for us un-engineer types there better be a lot of pictures and your home phone number.

but I would at least like to see what you got. It sure would be handle.

**hobkirk** · 03-26-2006, 05:54 PM

preamble -

I for one am very interested in your setup - triggers, relay, 12V source, etc.

Loring -

More than the pictures, I would love to find the details of the relay itself. I have lots of experience with 12VDC relays in cars and trucks but zero on AC systems.

I have a 2HP 240V Grizzly DC system that I'd like to trigger either with a 120V AC switch. I don't even know if a 40A 120V relay would handle a 240V system.

Any help would be appreciated! Thanks.

**preamble** · 03-26-2006, 08:57 PM

It's not that much different that a 12 volt system, other than we're talking higher voltages and higher amps - which can be lethal!
But working on such systems without power applied is safe.

What you are talking about is pretty simple assuming you have the right relay.
Lets say you find a relay capable of 240vac and the amperage draw of your DC (which you didn't mention). As you know from the 12vdc systems, there is the coil voltage (usually a lower voltage and lower power consumption (amps), and the contact rating (amps/volts). When power is supplied over the coil it triggers the contact thus turning on the DC. Power is supplied to the coil much as it is to a light bulb - both hot and nuetral (or DC + and -) are applied across the coil.
What you specified is that apon applying 120vac across the coil you want to control 240vac. Just be sure to get a relay with a coil voltage of 120vac (amperage is almost non important here as most relays don't consume that much on the coil side) and a contact rating of 240vac (wich supports an amp rating greater than the draw of your DC.

So lets say that your DC consumes 10 amp.
A 120vac coiled relay with a 240VAC contact cable of supplying 15 amp draw would work. You want to get a relay capable of at least 20% higher an amp rating than what your load (DC) is.

I was able to find a good source on eBay for my relay.
The biggest difference on my application is that I controlled the relay with 12VDC, not 120VAC. This allowed me to run the low voltage to each of the blast gates which allows the use of lighter wire (and is much safer).

I assume that you have a reason for wanting to control the DC with 120VAC.

**hobkirk** · 03-26-2006, 09:37 PM

preamble -
THANKS, THANKS...
Actually I like your idea of using 12V, but my Q was to Loring and I surmised he was using 120. I planned on reading up a little on alarm systems before I asked my dumb questions...

**just4funsies** · 03-26-2006, 10:01 PM

If you want to use low voltage in your trigger circuit, there is no advantage to using DC. 12V or 24V AC would work just as well, and then there is no need for a rectifier circuit (which may burn out with continuous use). A 120/12-VAC transformer would be all that is necessary, provided the coil in your relay starter is rated for AC current (a DC coil in an AC circuit would buzz, and drive you slowly insane

).

**LCHIEN** · 03-26-2006, 11:21 PM

Originally posted by hobkirk

preamble -

I for one am very interested in your setup - triggers, relay, 12V source, etc.

Loring -

More than the pictures, I would love to find the details of the relay itself. I have lots of experience with 12VDC relays in cars and trucks but zero on AC systems.

I have a 2HP 240V Grizzly DC system that I'd like to trigger either with a 120V AC switch. I don't even know if a 40A 120V relay would handle a 240V system.

Any help would be appreciated! Thanks.

The relay was designed for Air conditioning work - doesn't care what voltage is switched as it was designed for 120/240/480V

The coil can be bought 12V, 24, etc, but I chose 120V so I could drive it directly from my remote control, I could have used 24V and a doorbell or thermostat transformer but this eliminated one more part to wire up. These are rated for AC control, but DC should work, too.

I am working on the documentation and will post before too long.

I'll include how to switch a 240V DC, also.

remote-Relay for DC

remote-Relay for DC

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