AFFF
Established Member
For years I have been relying on old domestic vacuum cleaners to suck up the sawdust generated by my power tools, not the best solution. So recently I decided to build a dedicated dust extraction system that I can move around and put in the back of my truck when doing onsite jobs.
Its based on a Vacmaster 20lt 1250 watt vacuum cleaner combined with a vortex dust separator and plastic drum to hold the sawdust. All located inside a custom built trolley with lockable castors. I liked the Vacmaster as it had a PTO facility. However, there is a drawback with the PTO system. You can only power tools through it with a maximum wattage of 1740w (I have 2 tools that exceed this wattage, my table saw and my planer/jointer). This would be the case with any vacuum/PTO system that runs through a single 13 amp UK standard plug as the maximum wattage you can draw is 3 kw and this power has to be shared between the tool and the vacuum.
So, I designed a custom power sensing device that takes power from its own 13a plug/socket to supply the tool you are running (now max 3kw) and when it senses a current flow it applies a small load on the PTO which turns the vacuum on.
The current sensing is done by a nifty little current sensing switch and the load is a 1k Ohm 100w finned, chassis mounted resistor. This consumes 57.6 watts at 240v which is enough to trigger the PTO. The system also has a 40mm cooling fan to aid heat dissipation. The resistor is also mounted onto a 1mm thick 35 sq. cm plate with thermal transfer compound to act as a heat sink. If anybody is interested in the component details then let me know and I'll supply them.
Here's some pictures, probably makes more sense than my words
Its based on a Vacmaster 20lt 1250 watt vacuum cleaner combined with a vortex dust separator and plastic drum to hold the sawdust. All located inside a custom built trolley with lockable castors. I liked the Vacmaster as it had a PTO facility. However, there is a drawback with the PTO system. You can only power tools through it with a maximum wattage of 1740w (I have 2 tools that exceed this wattage, my table saw and my planer/jointer). This would be the case with any vacuum/PTO system that runs through a single 13 amp UK standard plug as the maximum wattage you can draw is 3 kw and this power has to be shared between the tool and the vacuum.
So, I designed a custom power sensing device that takes power from its own 13a plug/socket to supply the tool you are running (now max 3kw) and when it senses a current flow it applies a small load on the PTO which turns the vacuum on.
The current sensing is done by a nifty little current sensing switch and the load is a 1k Ohm 100w finned, chassis mounted resistor. This consumes 57.6 watts at 240v which is enough to trigger the PTO. The system also has a 40mm cooling fan to aid heat dissipation. The resistor is also mounted onto a 1mm thick 35 sq. cm plate with thermal transfer compound to act as a heat sink. If anybody is interested in the component details then let me know and I'll supply them.
Here's some pictures, probably makes more sense than my words
