How to program microcontroller for soft start three phase induction motor.

doinfinity · Nov 30, 2007

Hi,

I am planning to start building a soft starter by using microcontroller which can be used on a three phase induction motor. I have built one in analog circuit.

The microcontroller is used to generate increasing gate pulse synchronized with the input which used to trigger the thyristor, the input to the microcontroller is the three phase power supply.

I have no idea on any microcontroller. What kind of microcontroller is suitable for this project and how should I program the microcontroller? Any useful material or website have tutorial on this topic?

Any sample code available for used at this project?

Thanks for your help in advance.

bobledoux · Nov 30, 2007

Microchip.com lists 13 application notes for motor control of induction motors. Four of the notes are specifically for 3-phase motors.

doinfinity · Nov 30, 2007

The picture showed below is single phase control circuit and power circuit. How should I start by using a microcontroller to function as same as the control circuit within the red line? The control circuit is used as firing circuit to drive the inversely parallel connected thyristors in the power circuit.
**broken link removed**

blueroomelectronics · Nov 30, 2007

As a previous post said, have you looked at the Microchip app notes?

doinfinity · Nov 30, 2007

blueroomelectronics said:
As a previous post said, have you looked at the Microchip app notes?

Ya, I have take a look at Microchip application notes about induction motor. It does recommend some microcontroller which suitable for induction motor control. As I have no any knowledge on programming the microcontroller, i don't really clear on how to start program and what should i notice when programming.

blueroomelectronics · Nov 30, 2007

It's not a trivial project, you'll need to spend some time and learn programming. Lighting an LED is a good start, so is using the free simulator that's part of the free MPLAB IDE.

doinfinity · Nov 30, 2007

blueroomelectronics said:
It's not a trivial project, you'll need to spend some time and learn programming. Lighting an LED is a good start, so is using the free simulator that's part of the free MPLAB IDE.

hi blueroomelectronics,

Ya, i am now start learning to program microcontroller by simulation. I am trying to program PIC16F84 to light an LED. Does the MPLAB IDE can simulate the LED turn on?

blueroomelectronics · Nov 30, 2007

No it's a software sim, but you can watch the pin(s) using a watch window.
PS don't bother with the 16F84 it's an antique. The 16F628A is the modern replacement.

doinfinity · Nov 30, 2007

blueroomelectronics said:
No it's a software sim, but you can watch the pin(s) using a watch window.
PS don't bother with the 16F84 it's an antique. The 16F628A is the modern replacement.

Thank you for your help.

But I wonder is there any tutorial file teach how to use MPLAB IDE to do the sim? As I am first time using this software, i know how to write the code, but don't know what is the next step.

blueroomelectronics · Nov 30, 2007

Post your code, let me see what I can come up with.

doinfinity · Nov 30, 2007

blueroomelectronics said:
Post your code, let me see what I can come up with.

Hi blueroomelectronics, below is how the code looks like:

;*****Set up the Constants****

STATUS equ 03h ;Address of the STATUS register
TRISA equ 85h ;Address of the tristate register for port A
PORTA equ 05h ;Address of Port A
COUNT1 equ 08h ;First counter for our delay loops

;****Set up the port****

bsf STATUS,5 ;Switch to Bank 1
movlw 00h ;Set the Port A pins
movwf TRISA ;to output.
bcf STATUS,5 ;Switch back to Bank 0

;****Turn the LED on****

Start movlw 02h ;Turn the LED on by first putting
movwf PORTA ;it into the w register and then ;on the port

;****End of the program****

end

blueroomelectronics · Nov 30, 2007

I've got to run for lunch but will edit and repost later today.
Hint use a list & include at the beginning...

blueroomelectronics · Nov 30, 2007

I've changed the code and the PIC somewhat, but here's a screenshot of MPLABs Simulator

doinfinity · Nov 30, 2007

blueroomelectronics said:
I've changed the code and the PIC somewhat, but here's a screenshot of MPLABs Simulator

Thank you. I will try to do it in MPLAB IDE. As I am new to microcontroller and now just starting to learn how to program, am I able to learn the technique and complete my project for the soft start induction motor within 1 week? As this is the period for me to finish it.

doinfinity · Dec 1, 2007

Can Motorola M68HC11 used as firing circuit to control the phase angle of thyristor for soft start purpose?

Nigel Goodwin · Dec 1, 2007

doinfinity said:
Can Motorola M68HC11 used as firing circuit to control the phase angle of thyristor for soft start purpose?

I don't see why not?, I would expect any micro-controller to be capable of the task.

doinfinity · Dec 1, 2007

Nigel Goodwin said:
I don't see why not?, I would expect any micro-controller to be capable of the task.

Hi Nigel Goodwin,

Since any micro-controller has the ability to do the task, how do i learn so that i can program the micro-controller? As I considered as a novice to micro-controller programming. Any guideline for me, so that i can learn step by step, finally can program the micro-controller so that it can operate as firing circuit to trigger the thyristor. Thank you in advance.

Nigel Goodwin · Dec 1, 2007

You need to learn to program the specific micro-controller you have, you need to start simple and work up, flashing an LED is the usual first step!.

doinfinity · Dec 1, 2007

Nigel Goodwin said:
You need to learn to program the specific micro-controller you have, you need to start simple and work up, flashing an LED is the usual first step!.

Thank you. I will start from simple project and learn through it.

One more question, is any micro-controller includes the M68HC11 able to perform the following task: Input 3 phase power supply to the micro-controller and the micro-controller generate 6 gate pulse which use to trigger thyristors so that soft starter is achieved? Is this just the matter of programming?

Nigel Goodwin · Dec 1, 2007

As you're looking at very slow frequencies (50Hz or 60Hz), it should easily be possible to do it in software - but obviously choosing a device with helpful hardware could make it a simpler task.

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