Dust collector relay box
I built this dust collector for my table saw. On my homemade machines I just add an extra socket to plug the dust collector into, but the table saw runs on 240 volts and the dust collector runs on 120 volts. I had previously hooked a mini dust collector between one of the phases and ground to get 120 volts, but that is risky because, if the ground connection breaks, this sends 120 volts into the chassis of my table saw.
So I built a relay box to turn on the 120 volts when it gets 240 volts from the table saw.
I used a solid state relay (Imitation Fotek, $3 from china). The relay needs 3-24 volts DC to activate and can switch up to 25 amperes AC. A 9 volt battery works fine to activate it, as does an old 5-volt cell phone charger AC adapter. The cell phone charger adapter can also run off 240 volts so it's perfect for the job. I tested it on the workbench using a motor that came from this machine.
Then wiring it up. Conveniently, the electrical box has a strain relief already built in, which I'm using for the main cable. This cable powers one of the sockets directly (always on), while the "hot" side for the other socket goes through the solid state relay. So one socket activates when the saw is switched on, the other acts more like an extension cord.
I don't have any convenient power outlets near the table saw, so I put a long power cord on the relay box. The extension cord function will come in handy for plugging in other tools.
The combination of cell phone charger and solid state relay was a good way to handle this. Mechanical relays that run on 240 volts are harder to find and more expensive to buy.
An added bonus is that when I turn off the table saw, the filter capacitors in the cell phone adapter still provide power for a few more seconds, so the dust collector keeps running for a few more seconds to help clear out dust.
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