LCD Backlight Dim while driving motor using IR2130

[losturcos]

Hello,
I have a circuit to drive a motor with IR2130 circuit. I am driving IR2130 by a PIC microcontroller.
Also I am driving an LCD in the same circuit to display some state messages.
The 60V supply is obtained from 5 pieces of 12V batteries for driving the motor, and the 24 V supply
for PIC, LCD, 7815, 7805 etc. is obtained from second of the batteries.
The circuit is driving the motor and the LCD without problem but when I want to stop the motor manually
(to test the feedback from the IR2130), the LCD starts to dim.
What can be causing this?
Thanks.

 

[mrarslanahmed]

What is the load rating of the motor?

I dont think there is flaw in power supply..can you provide the schematics?

 

[bigdogguru]

The circuit is driving the motor and the LCD without problem but when I want to stop the motor manually
(to test the feedback from the IR2130), the LCD starts to dim.
What can be causing this?

You maybe experiencing Counter/Back EMF due to the inductive properties of the motor?

Have you implemented any Counter/Back EMF protection/prevention circuitry?

Can you post a schematic of the motor control section of your design?

BigDog

 

[mtwieg]

How are you supplying the backlight? Is it regulated at all?

 

[jibon]

Common mode rejection filter should reduce back emf problem, Sometimes free wheeling diode is not sufficient to reduce back emf.

 

[alexxx]

when I want to stop the motor manually
(to test the feedback from the IR2130), the LCD starts to dim.

A reasonable grounding scheme is demanded in such cases. Analog and digital ground should be merged in the correct place.
Are you using a printed or a bread board? Apart from the schematic, it would be useful to give some details of the board as well.

 

[losturcos]

Thanks for your replies.
First of all I want to make a clarification. The LCD doesnt have problem while the motor is running.
The dimming appears when I try to stop the motor with my hand while it is trying to run.
As for the questions:
@alexxx: it is a printed board. The mosfets' gnd is seperated with the digital gnd by a 20 cm cable
which obtains a 0.2R .
@jibon: Can you give me a clue about the common mode rejetion filter, I will search it, but I wont
reject any helps .
@mtwieg: I have 5 batteries of 12V/7A in series to obtain 60 VDC, I get the GND from the first battery's
GND, I get the 2nd battery's (+) output for 24 VDC (from this I regulate the 5VDC and 15VDC), then I get
the last battery's (+) for 60VDC. The 24 VDC is regulated to 5 and 15 Volts by 7815 and 7805.(Maybe
some more capacitors I should have used at the regulation circuits).
@mrarslanahmed, @bigdogguru: I will try to supply a circuit schematic tomorrow, but actually, the schematic
is similar with the sch at the IR2130 application note. And about the motor, the motor is an old elevator motor;
4kW. I am not sure about the other details.
Waiting for your replies. Thanks for interest.

 

[mtwieg]

Thanks for your replies.
First of all I want to make a clarification. The LCD doesnt have problem while the motor is running.
The dimming appears when I try to stop the motor with my hand while it is trying to run.

This is expected, since it will only draw significant current when it's under load.

@mtwieg: I have 5 batteries of 12V/7A in series to obtain 60 VDC, I get the GND from the first battery's
GND, I get the 2nd battery's (+) output for 24 VDC (from this I regulate the 5VDC and 15VDC), then I get
the last battery's (+) for 60VDC. The 24 VDC is regulated to 5 and 15 Volts by 7815 and 7805.(Maybe
some more capacitors I should have used at the regulation circuits).

This doesn't answer my question though. How is the backlight connected to the supplies? Which supply rail is it connected to? Is it just a raw string of LEDs with a current limiting resistor, or is there some kind of built in regulator in the LCD?

 

[ZASto]

12V/7Ah (60V/7Ah) on 4KW motor?

You are killing your batteries. There is no way for 7Ah battery to deliver 66.6666666 A without SIGNIFICANT voltage drop on it's internal resistance.

 

[losturcos]

I have prepared a simplified schematic.
View attachment Bridge.PDF
View attachment LCD.PDF

 

[jibon]

12V/7Ah (60V/7Ah) on 4KW motor?

You are killing your batteries. There is no way for 7Ah battery to deliver 66.6666666 A without SIGNIFICANT voltage drop on it's internal resistance.

This is correct, 7AH battery should not deliver 66 AMP current due to its internal resistance.

 

[losturcos]

The motor is 220VAC 50 Hz. In normal running it is using 8-9A. The circuit will not work for a long time.
It will only work for about max. 30 seconds, and I am driving in low speed, low frequency (5-6 Hz).
No problem about it.

 

[jibon]

The circuit is driving the motor and the LCD without problem but when I want to stop the motor manually
(to test the feedback from the IR2130), the LCD starts to dim.

You said "when I want to stop the motor manually" ..
Is it possible to stop the motor from MCU by disabling the signals? Or you are already stop the motor from MCU. And also is it possible to slow down the speed to very low frequency before stop the motor?

 

[losturcos]

Actually I am trying to see the feedback current when the motor cannot run because of any external cause.
So I am not stopping the motor from MCU.

 

[jibon]

Actually I am trying to see the feedback current when the motor cannot run because of any external cause.
So I am not stopping the motor from MCU.

So the point is, Somehow the motor is stopped forcefully from out side when the MCU tries to run the motor right?
If this is the situation then the motor should **** too much current from battery which then cause the voltage drop. Am I right?

 

[losturcos]

Yes, it seems to be right, but we have measured the voltage, the drop is only 1-2 volts.
It drops from 25 to 24V.

 

[jibon]

Yes, it seems to be right, but we have measured the voltage, the drop is only 1-2 volts.
It drops from 25 to 24V.

Does LCD backlight starts to dim or the LCD Character starts to dim?
In the schematic, did you use 100uF capacitor at the output of 7805?

 

[losturcos]

No, we didnt use 100 uF capacitor, that may be a solution. I will try that, but I have damaged the board while
I am trying another function . After I prepare a new one, I will test and write the feedback here.

 

[jibon]

Ok, i am here. thanks.