View Full Version : Relay Circuit for Dust Collector

03-16-2006, 06:25 PM
Looking for detailed instructions on building a relay box to turn my dust collector on/off using output #4. I've read the manual, but don't follow their plans. My dust collector runs off of 220V. Any help would be great.


03-16-2006, 06:31 PM
Hi Kevin
Call shopbot they sell a realy card that works with the alpha control box .It will do that .

03-16-2006, 06:38 PM
Stephan - Are you saying that I would run my power cord for my Dust Collector inside the control box and attach it to the card I would get from Shopbot?

03-16-2006, 07:34 PM

If you're trying to control a 120VAC device, you might try using a Solid State Relay (SSR), which is the way that I normally control external machines from any process-control computer (like the Shopbot Control Board). The SSR is mounted in its own tamper-proof enclosure with a control line going to the Shopbot Controller and the necessary AC lines going to a power panel.

If you're controlling a 240VAC device, the SSR can be used to control a 240VAC double-pole relay. Never use a single SSR to control a 240VAC device (at least in the United States where each 120V side of the 240VAC circuit must be controlled). In fact, if you're controlling a 240VAC device, stop reading this post and get help from a qualified electrician.

If you're still reading this, then you're trying to control a 120VAC device.

Most SSRs have four terminals. Two of the terminals are control connections and two of the terminals are AC connections. One of the control connections (usually marked '+') is connected to the 5VDC voltage supply on the Shopbot Control Board. The other control connection (usually marked '-') is connected to the output terminal of your choice on the Shopbot Control Board. (Shopbot's command: SO, port number, 1/0 controls the SSR.)

Okay, we're half way finished.

One of the SSR's AC connections, sometimes marked 'L' or 'Line' connects to the HOT side of your AC circuit. The other AC connection connects to the HOT or LINE side of the device you're controlling. If you're using a standard three-prong American style plug, the HOT or LINE connection goes to the more narrow of the two plug lugs. The other side of the device you're controlling goes to the NEUTRAL side of the AC line, which is the wider of the two AC lugs. To be safe, put an in-line fuse between the SSR and the HOT/LINE connection of the device that you're controlling.

Be sure to use an SSR that has zero-voltage crossing detection. That means that the device will be turned ON/OFF when the AC sine wave crosses the zero point, meaning that you won't have to worry about the circuit generating electrical noise.

As always, to be safe, have an electricial check your work before turning things on.

03-16-2006, 08:03 PM
Hi Kevin
With the shopbot relay you would only switch the hot wire of what ever your hooking up and you will have to watch how many amps your dust collector draws . So if you can find the relays that Mike is talking about then that would be an option too. I rigged mine up with a remote control switch that works on an RF signal from a keychain remote , becouse I have other things hooked up to the dust collector .That way I can turn on the collector from anywhere in the shop.

03-16-2006, 08:04 PM
Mike - Thanks for the reply and yes I'm trying to control a 240VAC device, sounds like I need to call my local electrician for a bit of help in getting this up and running.

Thanks for the help.

Ryan Patterson
03-16-2006, 08:24 PM
The relay circuit in the Shopbot user manual works good. You can buy all the parts at Radio Shack. Once you have this circuit you can use it to control a 240 double-pole relay as Mike suggested. I will try and remember to take some pictures of my relays and post them tomorrow. The parts from Radio Shack will cost about $8.00 and a 240 double-pole relay should cost about $30.00.

03-17-2006, 12:17 AM
The fun of connecting "slow-starting" dust collectors....... Do not underestimate how long it takes a dust collector to get up to full speed, and how much current it draws while doing this. Our dust collector draws 9 amps while running, but it starts off drawing 60 amp! We had to get a slower tripping "circuit breaker" for it because it consistently tripped a standard 20 amp breaker while starting. A tip with your new relay is to wait till the dust collector is fully up to speed before trying to switch it off - your relay contacts will thank you for that.