Building an Ammeter with TORQUE!

S

skk

Guest
Hi ..... I need help in building what is basically an ammeter with
TORQUE!!!!

The current from each phase of the household current has to be summed,
averaged and displayed through a pointer that rotates through 75
degrees. The device shall take the output of three current
transformers, find the average and create an output that shall drive a
servo motor between zero degrees and 75 degrees.

When the current being drawn is zero, the rotor position shall be at
zero degrees and when the current is max (as set by user), the rotor
shall be at 75 degrees. Any intermediate voltage should correspond to
an intermediate degree position.

There should be an option to set the maximum possible current drawn.
There should be a potentiometer to control the current at which the
rotor moves out of the zero degree position.
There should also be a test circuit that enables checking of the
movement of the rotor by simulating 0-max input.
All parts should be rugged and durable ... able to work continuously
day in and day out.

I need a total solution... a board to which I connect the leads from
the three current transformers and a servo motor spindle at the other
end to which I connect my pointer. I am a hobbyist with a limited
budget. Hope that someone on this board can assist.

Regards

Skk
 
"skk" <skk@cyber.net.pk> wrote in message
news:cdb7f52e.0309090007.6414139@posting.google.com...
Hi ..... I need help in building what is basically an ammeter with
TORQUE!!!!

The current from each phase of the household current has to be summed,
averaged and displayed through a pointer that rotates through 75
degrees. The device shall take the output of three current
transformers, find the average and create an output that shall drive a
servo motor between zero degrees and 75 degrees.

When the current being drawn is zero, the rotor position shall be at
zero degrees and when the current is max (as set by user), the rotor
shall be at 75 degrees. Any intermediate voltage should correspond to
an intermediate degree position.

There should be an option to set the maximum possible current drawn.
There should be a potentiometer to control the current at which the
rotor moves out of the zero degree position.
There should also be a test circuit that enables checking of the
movement of the rotor by simulating 0-max input.
All parts should be rugged and durable ... able to work continuously
day in and day out.

I need a total solution... a board to which I connect the leads from
the three current transformers and a servo motor spindle at the other
end to which I connect my pointer. I am a hobbyist with a limited
budget. Hope that someone on this board can assist.

Regards

Skk
Click to expand...
IIWY I would consider something like PIC with enough ADCs and stepper motor
from those old 5.24" floppy drives.

Some of those steppers had a small metalic arm on the axis that allows you
to mount IR sensor(from the same drive that you scavenged stepper). With a
bit of rework, you can use the same arm as an optical pointer and to sense
"position 0".

The rest should be easy enough. You sample the three phase inputs, calculate
average and rotate the stepper accordingly...


Regards

Branko
 
"skk" <skk@cyber.net.pk> wrote in message
news:cdb7f52e.0309090007.6414139@posting.google.com...
Hi ..... I need help in building what is basically an ammeter with
TORQUE!!!!

The current from each phase of the household current has to be summed,
averaged and displayed through a pointer that rotates through 75
degrees. The device shall take the output of three current
transformers, find the average and create an output that shall drive a
servo motor between zero degrees and 75 degrees.

When the current being drawn is zero, the rotor position shall be at
zero degrees and when the current is max (as set by user), the rotor
shall be at 75 degrees. Any intermediate voltage should correspond to
an intermediate degree position.

There should be an option to set the maximum possible current drawn.
There should be a potentiometer to control the current at which the
rotor moves out of the zero degree position.
There should also be a test circuit that enables checking of the
movement of the rotor by simulating 0-max input.
All parts should be rugged and durable ... able to work continuously
day in and day out.

I need a total solution... a board to which I connect the leads from
the three current transformers and a servo motor spindle at the other
end to which I connect my pointer. I am a hobbyist with a limited
budget. Hope that someone on this board can assist.

Regards

Skk
Click to expand...
This is not a bit of help it's a major design project and there is
insufficient information to even start. You need more specification like
what operating voltage, what current range is it supposed to work for. There
are three different jobs here, monitoring the current, limiting the current
and building a simulation rig that pretends to be the current.

Limited budget means lots of time. Commercially I would think a prototype
device capable of controlling current at around the 100ma level to the rough
spec you have given would cost (as a very rough guess) about Ł3000 as a
prototype. Thats one of the three jobs, total guesstimate, Ł10,000.

I don't think this one is going anywhere :)
 
Some of these devices have RS232 outputs that (perhaps with further
processing) be used to drive the servo.


http://www.electronicstalk.com/news/anc/anc164.html

http://www.keyitec.com/Keyitec5C.html

http://www.microsol.com/pdfs/AIM-020.pdf


"skk" <skk@cyber.net.pk> wrote in message
news:cdb7f52e.0309090007.6414139@posting.google.com...
Hi ..... I need help in building what is basically an ammeter with
TORQUE!!!!

The current from each phase of the household current has to be summed,
averaged and displayed through a pointer that rotates through 75
degrees. The device shall take the output of three current
transformers, find the average and create an output that shall drive a
servo motor between zero degrees and 75 degrees.

When the current being drawn is zero, the rotor position shall be at
zero degrees and when the current is max (as set by user), the rotor
shall be at 75 degrees. Any intermediate voltage should correspond to
an intermediate degree position.

There should be an option to set the maximum possible current drawn.
There should be a potentiometer to control the current at which the
rotor moves out of the zero degree position.
There should also be a test circuit that enables checking of the
movement of the rotor by simulating 0-max input.
All parts should be rugged and durable ... able to work continuously
day in and day out.

I need a total solution... a board to which I connect the leads from
the three current transformers and a servo motor spindle at the other
end to which I connect my pointer. I am a hobbyist with a limited
budget. Hope that someone on this board can assist.

Regards

Skk
Click to expand...
 
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