Help on reading motor Current to my PLC controller

Actually i doing it to my PIC controller not PLC controller. please give me some hint on the current reading on motor thank you

Ejida,

In that case you need to select a PIC with an on board D/A convertor

Al

ejida:

I HAD TRYED TO GIVE YOU A HINT ON USEING CURRENT TRANSFORMERS

TO CONVERT YOUR MTR DATA TO MILLIVOLTS THEN USEING DAC

TO CONVERT TO YOUR SYSTEM THIS WOULD PROVIDE ISOLATION ALSO.

RED.

Hi ejida,

You need to obtain an analogue to digital convertor input module for your PLC. Without more information this is as much help as I can give you

regards

Al

You will need an AC current to dc current or volts converter.

See

http://www.amelec-uk.com/wwwroot/datasheets/adp451sp.pdf

Thank you all for reply.

but the ADC i needed is input can be 240VAC current variasion is from 1 to 5 ampere . the output of the ADC i need is few digital (on and off ) signal which i can put into my PIC controller

Ejida,

If you only want to know if the motor is drawing current or not then put a relay with a 240v AC rated coil in series with the motor and put 5v dc on one side of the normally open contact and the other side as your on/off signal to your PIC

Al

How about a current transformer + a rectifier + smoothing RC + potential divider (for scaling) + LM3914 LED bar graph driver as an ADC? You could scale it to use just, say, the low order 5 bits. It's not an encoded output, so it's very wasteful of input lines, but it'd work as a cheap'n'dirty solution. Or you could run all the outputs to the PIC via an encoder. I looked at the LM3914 because it only costs about €2.

I'm dashing out now - will try to help out later if you need it.

My idea of the ADC is like i need 1.0 Amp of give 1 signal to PIC . 1.2 AMP to another signal to PIC and 1.4AMP to another signal to PIC .. and so on ... this is allow me to do controlling in PIC output .

but so far i also no idea how to make all this different ampere to different signal to my PIC

The LM3914 I suggested can do that for you - with appropriate input scaling. On the road now, will get back later.

JohnDG

Lee Dickens on www.lee-dickens.biz make quadruple level trip amplifiers that will give you four volt free contact that you can set to any current you require. You can then power the contacts from a 5 voltdc source to give you a four independant signals.If you use five of the quadruple trip amplifiers you will hav 20 independant signals.

You can by a power factor correction relay for less money. This will connect directly to your ac voltage and current and give you up to 20 volt free conats at different pf levels to switch your capacitors.

the main question is why do you have to a power factor correction on the signle phase motor , to you want to reduce the power consumption are planning to change the speed of you single phase motor,remember that you have already a capacitor in you single phase motor which compensate the starting and running ofn your single phase.so hwat is really the omain objective of your project.

My project title is " power factor improvement for a single phase motor "

what i try to do is for variable of single phase motor load. i will try to make the power factor stick to 0.9 power factor by adding different amount of capacitor to the single phase motor.

Since variable of load will make the motor have different variable of ampere . these why i try to read the ampere and make different signal to my PIC controller and let my PIC controller to decide the amount of capacitor to the motor.

My problem is i can not find a suitable current ADC for this purpose. which will output to my PIC controller

1. Get a current transformer (CT) (ie. www.toroid.com ) 300:1 should do it. (Max secondary voltage at 90 amps = 4.5V)
2. Pass one lead of the load through the hole.
3. Put a diode bridge following the CT
4. Put a load resistor on the DC side of the bridge. The CT spec sheets should show you how to calculate the load resistor and what you will get out based on the turns ratio (turns ratio =1).
5. Ground the neg side of the bridge
6. Put a series resistor going into your pic analog to digital converter, maybe 1K ohm

Good luck with your project.

May I suggest a slightly different approach? What about sampling the input voltage at the input of combined capacitor/ motor setup and sample the current via a voltage from a resistor across a current transformer, and use these voltages on the inputs of an XOR? The result would give you a pulse whose width represents the amount of phase angle, with no pulse being in phase. Sampling which voltage is at a zero crossing at the begining of the pulse would indicate if leading or lagging.

Your project sounds interesting.

thank you all for reply me. yeah i will refer all the information you all give to me. really thank for you all help . thank thank