I've just stumbled-across the datasheet for an ACS712, a very cheap hall
effect current sensor. It seems that FW rectifying the output and then
using a comparator to drive a relay would be a simple way to build a
slave switch for a dust extractor. Has anyone tried it?

On 14/07/2020 19:42, wrote:
I've just stumbled-across the datasheet for an ACS712, a very cheap hall
effect current sensor. It seems that FW rectifying the output and then
using a comparator to drive a relay would be a simple way to build a
slave switch for a dust extractor. Has anyone tried it?

Not specifically with that device, but have you seen:

http://wiki.diyfaq.org.uk/index.php/...tivated_switch

--
Cheers,

John.

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On 15/07/2020 14:02, John Rumm wrote:
On 14/07/2020 19:42, wrote:
I've just stumbled-across the datasheet for an ACS712, a very cheap
hall effect current sensor. It seems that FW rectifying the output and
then using a comparator to drive a relay would be a simple way to
build a slave switch for a dust extractor. Has anyone tried it?

Not specifically with that device, but have you seen:

http://wiki.diyfaq.org.uk/index.php/...tivated_switch

Thanks, I vaguely recall seeing it earlier but had forgotten about it.

Coincidentally, after a bit more thought, I decided to go the current
transformer route and ordered a CT, 5V SMPS and relay from China earlier
today (total cost less then £6 with shipping!). The hall-effect device
looked interesting but it's easier to get isolation with a CT. I'll
probably use a couple of transistors rather than CMOS because assembly
is slightly easier and CMOS can be troublesome in an electrically-noisy
environment.