disorder in lcd display

[bbd556]

: angry:: angry:: angry:: angry:: angry:
What do I do not know my life over a simple circuit
there is a control circuit for electric motor control of washing machine and electrical valve just got
Circuit components: micro + uln2803 + relay + conductor + character lcd
Blades on the relay 220ac Afth ticks attached to conductor, Once my 220 comes relays or sometime later strange letters comes my LCD
Micro plans to end'll run right, the problem is in LCD display case shows strange letters
i use snubber
program also wrote Baskom

 

[horace1]

assuming the display works correctly some of time, i.e. it is wired up correctly, corrupt characters could be caused by
1. electrical noise from electromechanical components such as relays, motors, etc
2. writing to the LCD too fast. LCD tend to be very slow devices in computer terms and putting a few milliseconds delay between write can help

 

[erio]

sounds like you have a noise across power supply problem
do you using decoupling capacitor across micro and LCD power supply pins?
use separate ground trace for micro and relay.
also spark from relay contact can make problem

 

[bbd556]

i use snubber
it isnt spark
but i think it is from power supply
i use this circuit in other project
i changed board little but designing not changed
it is work well
but the difference between them is power supply
could problem from power supply?

 

[erio]

well..maybe your power supply isn`t filtered good...try adding filter capacitor and decoupling capacitor in bridge diode
also check the power rating of your power supply.. make sure your power supply can provide enough current for your circuit.. a little dip on power supply rail is enough to ruin your micro and/or LCD..

 

[bbd556]

whats amount of capacitor?

 

[erio]

it depend on current in your circuit...
in my experiences 2200uF/amp...

well you can try adding a 2200uf...and 100nf for decoupling capacitor..

 

[bbd556]

i used it
i use a seperate filter module before power supply
dont u have any other idea?
thanks very lot erio & horace1 for replying

 

[erio]

well you saying that you using this circuit in other project and work good...the difference is on the power supply...can you try using the power supply in your "other project" and see if your circuit work well..

also try running your circuit in a battery...say a 12 volt battery and a 5 volt regulator...
goodluck

 

[bbd556]

thanks alot
*** will be with you for helping

 

[horace1]

could you be overloading your power supply, e.g. when you switch on a motor you get a surge of current which corrupts your data
erio mentions trying a battery - it is good idea - on a project using a load cell I ended up using battery power all the time - no amount of filtering would remove the power supply noise.

 

[bbd556]

battery for lcd or micro?