current sensing...
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Hello stampers,
Can anybody tell me an easy way to have a stamp i/o sense current flow of a 240v ac motor.
I need a logic 0 or 5v when the motor current exceeds 1 Amp or so. The motor generally draws
from 4 to 10 Amps when under load. Any help would be appreciated.
Chris
Can anybody tell me an easy way to have a stamp i/o sense current flow of a 240v ac motor.
I need a logic 0 or 5v when the motor current exceeds 1 Amp or so. The motor generally draws
from 4 to 10 Amps when under load. Any help would be appreciated.
Chris
Comments
I've had good success doing something similar (although it was a DC
application) using reed switches and a heavy conductor coil wrapped around
the reed. Things to watch out for are not winding the coil too tightly
around the reed (if a heavy current application the wire will expand and
break the reed glass) - wind so a bit of slop is there using something like
a screwdriver. Also use a wire size for the current carrying capacity of
the job having in mind the less the current the more the turns required to
operate the reed and vice versa.
Not sure how this will go with AC although but give it a try - the worse
that can happen is the reed will vibrate at 100hz (each cycle) be careful
with the coil - it will be at full mains potential! You can use a bridge
rectifier and filter cap (rated at >350VDC to smooth the supply feeding your
coil [noparse][[/noparse]still at mains potential!] or use a current sense transformer etc,.
If you need more info drop me a line and I'll sketch/fax it to you.
Regards,
Bill
At 07:14 05-02-01 +0800, you wrote:
>Hello stampers,
>Can anybody tell me an easy way to have a stamp i/o sense current flow of a
240v ac motor.
>I need a logic 0 or 5v when the motor current exceeds 1 Amp or so. The
motor generally draws
>from 4 to 10 Amps when under load. Any help would be appreciated.
>Chris
W J Sherwood
Senior Electronics Technician
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E-mail: bill.sherwood@p...
the jameco cat. then you could use a ADC, opamp or comparitor for the
voltage leval needed. These coils fit arround the wire like a clamp on
amp meter. if you use the adc approach you not only have a high level
you can program but you can look for loose belts, bearings going bad (
the current will go up slightly over normal ) and log the data for
reff.
> Chris Anderson wrote:
>
> Hello stampers,
> Can anybody tell me an easy way to have a stamp i/o sense current
> flow of a 240v ac motor.
> I need a logic 0 or 5v when the motor current exceeds 1 Amp or so.
> The motor generally draws
> from 4 to 10 Amps when under load. Any help would be appreciated.
> Chris
writes:
> Another approach would be to use one of the current transformers in
> the jameco cat. then you could use a ADC, opamp or comparitor for
> the voltage leval needed. --clip
Not sure I understand how this would work... the output of the current
xformer would be a 60 Hz signal... how would you do this with an ADC,
opamp, or comarator without using an RMS convertor (AD637) as well? As
the current in a motor is not a pure sin wave doesn't this complicate
matters since the true RMS current is different than the average current?
wasn't aware that the motor would affect the input line like this.
agarb@j... wrote:
>
> On Sun, 04 Feb 2001 15:50:24 -0800 Larry gaminde <lgaminde@t...>
> writes:
> > Another approach would be to use one of the current transformers in
> > the jameco cat. then you could use a ADC, opamp or comparitor for
> > the voltage leval needed. --clip
>
> Not sure I understand how this would work... the output of the current
> xformer would be a 60 Hz signal... how would you do this with an ADC,
> opamp, or comarator without using an RMS convertor (AD637) as well? As
> the current in a motor is not a pure sin wave doesn't this complicate
> matters since the true RMS current is different than the average current?