Random lcd pattern.

[hjl4]

Ok so I have Nigels tutorial 11.1 burned in the 16f88, and everything works well.
But, now if I let the project sit ON for more then 10 seconds, the lcd displays a bunch of garbage, and then almost immediately returns to its program.
This happens in a pattern . When I move my hand over the circuit, it goes hay wire.
Any idea if it has anything to do with no solder breadboard???
Maybe stray capacitance??
I have clean 5V power supply,and 10k on RA0 to stabilize it a bit, use Int_Rc, and thats it. other then pot for contrast. Using Optrex 16x1 display.
Should there be any capacitors also hooked up to RA0????
If so why???
Chip is running at 8 mhz. Still learning, as I also tried 4 mhz with same results.
Thanks.

 

[mvs sarma]

Hi, Hjl4,

solderless bredboards are sometimes problamatic-- especially when the type of link wires for interconnection are of thinner gauge and cause intermittent connctions.

try replace them with sigle strand thicker wire and ensure that the wire is gripped in the socket. also put a 0.1uF disc cap across the Vcc anf Vdd points of the IC dirctly-- (not some whwere else and think that it will work form a far off point . similarly you may put a 2.2uF electrolytic across power supply tothe LCD Display at its power terminals.(pin1 and 2 generally)

make similar arrangements acorss power pins additional ICs if used.

 

[hjl4]

Thanks mvs sarma,

Yes I am using fairly small gauge wire(ribbon cable between breadboard and lcd display, approximately 8 inches of it.
I will make the recommended adjustments, and put a cap between vss and vdd, and one between + and - of LCD display.
Thanks, as I suspected the breadboard would have something to do with all this.

 

[mvs sarma]

Thanks mvs sarma,

Yes I am using fairly small gauge wire(ribbon cable between breadboard and lcd display, approximately 8 inches of it.
I will make the recommended adjustments, and put a cap between vss and vdd, and one between + and - of LCD display.
Thanks, as I suspected the breadboard would have something to do with all this.

Hi, in fact in our area we get a type of PCB looks like the same pattern of solderless bredboard but with tracks. once you solder IC base and LCD connector socket(14 or 16 pin) you can resonably be free of dry connections and later you can carefully pull out your IC or LCD for other use. try for one such if you get.

 

[hjl4]

Ok, mvs sarma,
I got the caps on, and it is now stable. Thanks for the help.
Now on to more complicated project, send result thru rf transmitter and receive it, and display results, on LCD.

Oh well, I'm at work, and can't really get into things right now, my boss can see me from where he is.

Thanks for the help.

 

[Nigel Goodwin]

Ok, mvs sarma,
I got the caps on, and it is now stable. Thanks for the help.
Now on to more complicated project, send result thru rf transmitter and receive it, and display results, on LCD.

Try the later tutorials, but NOT on breadboard!.

 

[hjl4]

Nigel, is there anything you haven't done with your tutorials.?

I just noticed that you have already done this, and even rs232 etc....

This is great.

Back to studying.
I mean work

 

[Nigel Goodwin]

Nigel, is there anything you haven't done with your tutorials.?

I just noticed that you have already done this, and even rs232 etc....

This is great.

Basically you tend to find that people are looking for the same things, so I simply documented mine in the tutorials.

 

[mvs sarma]

Basically you tend to find that people are looking for the same things, so I simply documented mine in the tutorials.

It might be simple for You to document it , Nicely.

THis amounts A LOT of help for those who are helplessly searching.-- for those who are hungry for proper info. We used to have some lecturers in telecom in service training, who used to usea common phrase"in such a way so that"

Instead , your tutorials are crstal clear and remove uncertainities in the minds of juniors.