Garbage values on LCD (16×2) with change in speed of DC motor

[Er. NGM]

Hello experts!

I've faced a problem in one of my recent projects based on 8051 containing a DC Fan (driven by N-MOSFETs) & 16×2 LCD..

The issue is that the LCD displays gabage symbols/values if the knobe of the fan is switched among Low, Medium & High. The microcontroller here is executing the code perfectly without any failure controlling other I/O devices as expected; only LCD behaves randomly.

I also tried connecting an electrolytic capacitor of 220uF/25V at power supply pins of LCD to keep the power to lcd unfluctuated but still LCD is not in control.

What could be included in the hardware so that LCD works fine??

Kindly provide a solution to this problem asap…

[Hari Prasaath K]

Check with the pin connections from mc to lcd are correct, if u have them connected them wrong there may be problem.

check the coding for lcd initialization, lcd command write, and lcd data write functions you provided are right and if so check with the delays between sending data to Lcd.

If u again face the prblm attach the circuit diagram and code.

[Er. NGM]

Thanks for the reply sir.

Actually all the connections are proper & LCD displays all the messages perfectly until the speed of DC motor is constant.

As soon as we switch the position of knobe on DC Fan from low to high or vice versa; the LCD starts showing some garbage characters after sometime. I guess this is a kind of EMI / inductive effect of back emf generated by DC motor which is forcing LCD to go uncontrolled & show some garbage values..

What do you say?

[Er. NGM]

Kindly reply guys, if you have had a similar experience or any idea about its solution..

It's really very important for me.. Because I am stuck with this problem & desperately need a solution..

[Ashutosh Bhatt]

connect one 0.1 uF capacitor very near to Vcc pin of 8051 micro controller

connect free wheeling diode (FWD) accross motor pins.

if this wont help. search on google for EMI protection 

[Er. NGM]

Thanks Ashutosh..

I actually connected a 33 uF cap at power pins of LCD earlier..

Now I'll try connecting freewheeling diode & 0.1 uF cap across power pins of DC Motor & microcontroller respectively; and then let you know the outome soon..

Thanks for the advice..

[Anonymous]

test

[Author]

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