This instructable shows you how to use remote ligth switch to power something that draws much more current. In my case am going to use it switch my dust collector on/off but it will work for anything up to 1.5kw on 220V (1 hp if you are on 110V).
Buying a remote switch would cost me around $100 by the time I paid shipping and taxes to RSA and then it would be too small to run my 2HP dust extractor.
Unfortunately I only decided to do the instructable after I have almost finished the project already, so the photos will mostly be of the almost completed project and sample parts from google searches.
Materials needed (and costs onverted to Dollars from Rands):
- Electrical cable ($0 had lying around)
- Electrical outlet to mount in the box ($3)
- Plywood, chipboard or similar the construct a box to house the circuits ($0 scrap pieces)
- Screws (Virtually free, $0)
- Electrical connectors (had in my garage $0)
- Gland to fix the feed cord to the box ($0.50)
- Fitting to turn any light into a remotely controlled light ($6)
- 220V contactor (I used Schneider electric TeSys k) ($16)
- Saw to cut the pieces to build the box
- Drill (20mm for the gland, 2.5mm to drill pilot holes for the screws)
- Screw drivers
- Crimping tool
- Wire strippers
- Utility knife
Step 1: Wiring Diagram
The current draw by my dust collector is 7.7 amps at 220v for a 1500 W induction motor, the start up current can be 5 to 10 times that. The largest remote control for 220V I could find was one for a lightbulb. It is rated at 150 W or about 0.7 amps. Clearly running the motor off this would fry the circuitry.
To cater for the very high motor start-up current I was advised that a contactor rather than a semiconductor relay would be a good option as it could handle large currents for short periods of time, ideal for starting a motor.
The contactor works by using an electro magnet to pull conductors into contact thus completing a circuit. Activating the contactor actually draws quite a bit of current (2 amps for the one I am using) for the fraction of a second it takes to close. Two amps is higher than the rating for the light fitting but I decided to take a chance seeing as it is for a very short period only. Once the contact is engaged the current draw is very low, well within spec of the light fitting electronics. I have been told that there is also an inductive current that is generated when the magnet in the contactor is dis-engaged, I have no idea the magnitude hereof so I ignored it (fingers crossed!). Supposedly it can damage sensitive electronics. I will see what happens and update this if required.
Having tested it ten or twenty times or so it seems to work fine. If after a few months it fails I will look into adding some form protection from the phantom inductive current.
Step 2: Building the Unit
Cut the pieces for your housing. I recommend something about 20X15X15 cm. I am sure you can make it smaller but this size felt comfortable for me to work with and maybe modify some of the internals at some stage.
Cut the hole for the outlet in what will be the front ( one of the +- 20X15 cm pieces) and drill the hole (20mm in my case) for the gland in another, that will be the back of the housing. Drill pilot holes for screws in these two pieces that will connect to the base plate (the third +- 20x15 cm piece).
Branch the incoming 220V feed Live and Neutral wires into two. Connect one branch to the porcelain light fitting according to the markings on the fitting. Mount the fitting onto the base plate, i just used hot glue, seems to work 100%. Connect the other live and neutral wires to the contactor in the incoming side (marked L1 and L2) in my case).
When choosing a remote control fitting make sure what you use don't just give a power signal and then stop the signal , because the contactor requires continued power to maintain the connection. That is why the light fitting is ideal. More electrically inclined DIY'ers will certainly be able to find a way around this. But I am not one of those.
Screw the remote controlled light fitting into the porcelain fitting. Connect two wires to the light fitting where the light bulb would have drawn power and connect those two wires to the signal input on the contactor (A1 and A2 in my case). There is no indication of L and N on the contactor so I don't think which one goes to A1 or A2 matters.
I wanted to solder the wires to the metal parts , but I was curious so I opened the remote control fitting. It seemed difficult to put it back together so I ended up taking the power for the contactor basically directly from the circuit board. The manufacturer was kind enough to leave two nice wires to do this. Ended up being much easier than trying to to solder inside the fitting.
Now mount the electrical outlet on the front panel, i used short dry wall screws as the screws supplied with the outlet was pretty useless. Connect the connector marked with an L to the contactor opposite to the incoming Live wire and the same for Neutral. Connect the ground wire from the incoming feed to the connecter marked E on the electrical outlet.
Feed the incoming cable through the gland and secure the gland in the back panel. I used hot glue here again. Secure the contactor and any other loose items to the base. I used drywall screws for the contactor and hot glue for everything else. Secure the front and back panel to the base using drywall screws and glue. A few clamps will make this operation much easier. Connect a plug to the cable. You should now having a working remotely operated switch that will carry the amount of current that your contactor is rated for.
Step 3: Testing the Unit With Larger Current
Connect the new box to an outlet and test the functioning. If you press the button marked "On" on the remote you should hear the contactor click into place and see a little tab on top of the contactor move from the "0" to the "1" position. And vice versa if you push the "Off" button.
Plug something into the outlet on your housing that draws a reasonable amount of current, say a drill or a sander and try the remote again.Testing the remote unit using a drill worked 100%. If I hold in the trigger on the drill switch and press the remote button the drill came on 100% as expected and switched off as expected.
However when trying it with the dust collector it didn't work as planned. The problem is that the dust collector has magnetic switch where if the power to the machine is cut from the mains while the machine is running it does not continue running when the power is switched on again. This is genarally a good idea, especially for a table saw, but it means that my dust collector remote control unit will not work (it works perfectly to switch it off when it is running, so that's good). This would have been the case with one of the store bought units as well.
The fix is to bypass the switch installed by the factory. If there is any overload protection built into the circuitry do not bypass it. My dust collector is quite simple so there is no overload protection. The bypass is very simple, I just replaced my remote control unit in the place of the original switch (I am thinking of moving the dust collector switch to my table saw as it pretty dangerous at the moment, if the switch is on and I power it up at the wall the the motor will come on).
Having bypassed the factory installed switch for the dust collector motor the remote control works perfectly! Now you can remotely switch off anything! But really the only thing I think it would be useful for is the dust collector.
Step 4: Close the Box and Start Using Your Remote Control!
Once you have the unit fully working close the housing with dry wall screws and glue. I recommed putting the top panel on only with screws that way it will be removable to make any modifications or repairs.
Buying an expensive unit from Rockler or similar will certainly give you a prettier solution. But there is plenty of space on my dust collector base so the bigger bulkier box is no problem. Also, it is fairly easy to upgrade the capacity of the unit by replacing the contactor with a larger one. All the contactors in the TeSys K range draw the same current from the signal source so if the light fitting works for this it will work for the larger ones too.
Happy remote switching!