Dust extraction – Part 2: Current sensor

In this part of the dust extraction build I will show the current sensor. This sensor measures the current that the tool draws and gives a signal to a central unit once it is higher than a set value. In order to leave the vacuum cleaner on during the machine spinning down a settable timer is added. Also I added a start stop circuit, witch can be used to manually start/stop the valve and vacuum.  This can be handy to clean the work table. These buttons are not placed on all sensor units.

 

This unit consists of 2 parts.

Part 1: the current sensor:

A current transformer (ASM-010) is placed around the live wire.

The output of this transformer is send trough a 50R resistance. This converts the output current of the clamp to a voltage. This voltage is then amplified and compared against a level set by the potmeter. After this a 555 timer is added to keep the suction active while the machines motor spins down.

Part 2: on / off buttons:

This part works with a set reset flipflop. This has 2 buttons connected to manually start / stop the dust extractor.

Total:

The output of the 2 parts are coupled together with 2 diodes to a transistor that pulls the interface line to the controller low when it wants to turn on the dust extractor.

 

The PCB I designed for this project:

In order to keep the potmeters in place I added a small 3d printed bracket.

Build in the enclosure:

The next part of this project will be the central unit.

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