Discussion in "8051 Discussion Forum" started by    anee    Apr 7, 2008.
Tue Apr 08 2008, 05:24 pm
#11
hi anee,

my lcd displayed da required msg a couple of times...but thereafter its just da bars..



i understand from the above sentence that for once your programme run perfectly... then afterwards it didnt..!!

the only problem then will be loose connection as Shashijoseph said..
try changing the cable between your uC and the LCD (dont rely on connectivity shown by a multimeter)
another possiblity cud be the crystall...
try changing the crystall (generally crystals do not bother u much but that still cud be the case...)... or at least check the contacts of the crystall if it is soldered properly..

the third option if u are not using the busy flag mechanism try increasing your delay loops..
 anee like this.
Tue Apr 08 2008, 08:30 pm
#12
Hello Anee,

Check the following:

1) any shorts between control pins(excess solder)

2) did you accidently remove or pull the lcd connector when prog was running

3) did you initialize the lcd to proper rows, once power is applied to lcd you have to

wait atleast 15-20 mSec for internal initializing, and send 30H (i,e single row setting) 3

times with 4.5 msec intervals- this is standard initializing procedure that has to be

followed.

4) when using LCDs use Molex 16 pin connectors (male and female pin headers)

5) did you try the prog on other LCD, borrow one from your lab or friend

6) still if it doesn't work, it may be damaged so buy a new one


Good luck

Arun
 anee like this.
Tue Apr 08 2008, 08:44 pm
#13


Oops.....when you can,avoid tantalums like plague.They are prone to leakage and when compared to ceramics are fairly 'slow'.They do have a speed advantage over hefty electrolytics but when choosing between 0.1uF ceramic or tant' always prefer ceramics.Ceramics also have a lower self inductance and are non-polar whereas tants' are essentially polarized(correct me if I'm wrong) and may lead to mishaps when reverse connected.They do have a size advantage over electrolytics though.
Amit..where did you get this info yaar?

sashijoseph


Hey Shashi,
The guys on 8052.com had suggested my friend to use tantalums. They said they were better when it came to eliminating noise on the uC circuits! And practically my friend did see a difference when he used the tantalums instead of ceramics! I dont remember the thread, but il do a search and surely post that here!!! I am so sorry for giving out wrong info!!!
Please accept my humble apologies.
And thanks for the info on the tantalums.
 anee like this.
Tue Apr 08 2008, 09:26 pm
#14
hi amit,

you are not totally wrong.... so cheer up!!!

there are some applications where tantulum has its advantages over ceramic and others... your friend must have seen the difference by using them around the main power circuit areas..!!!!
but as shashi said @ 0.1uF i practically never used a tant..


take a look here



There are numerous advantages to using tantalum capacitors over other types of capacitors. First, tantalum capacitors have a higher volumetric efficiency (CV/cc) when compared to other types of capacitors. For instance, a 10-microfarad tantalum capacitor can replace a 100-microfarad aluminum capacitor. Tantalum capacitors are easily mounted onto circuit boards, and give engineering designers the ability to place these components in closely-confined printed circuit board space, as well as utilizing tantalum capacitors' excellent power dissipation characteristics. Second, tantalum capacitors have superior frequency characteristics than many other types of capacitors, including aluminum electrolytics. A comparable CV tantalum capacitor has an ESR ten times better than an aluminum electrolytic capacitor. Third, tantalum capacitors are highly reliable - electrical performance qualities do not degrade over time. Tantalum capacitors do not lose capacitance unlike electrolytic capacitors - in fact, the shelf life for tantalums is regarded as unlimited. Fourth, tantalum capacitors don't wear out - in fact, if there is an imperfection in the dielectric layer of a tantalum, the resistance of the manganese dioxide layer will typically convert to a form that is even more resistive. The new oxide form plugs up the faulty region and results in a reduction in current flow. Finally, tantalum capacitors have an excellent wide operating range, from -55 degrees Centigrade to +125 degrees Centigrade, with a minimal amount of degradation in electrical properties throughout this range.



practically i prefer them when operating at high frequency above or around 50Mhz..
plus sometimes around the power points (vcc-gnd) but never used as small as 0.1uF cant say why
Tags using Tantalum capacitor
Tue Apr 08 2008, 09:43 pm
#15
No problems Amit......you are partly right though.Tantalums will work better where you use electrolytics like 10uF,100uF etc.But for 100nF or so,it's ceramic always.
Tue Apr 08 2008, 10:26 pm
#16
hey anee, did u face dis problem: when u checked d lcd module independently, it worked fine, n wen u put it into ur main program or called it, then its not working??
if yes, then jst check if u hav put d "RET" statement at right place. actually, i did dis mistake n spent 2-3 hours to locate dis bug.
 anee like this.
Tue Apr 08 2008, 10:55 pm
#17
hmmm.....hey...dat can be a possiblity...bcz once da prog worked da 1st time...i went beserk n made a whole lot of changes..i wanted to see whether da lcd displays a specific msg when a specific button is pressed...n thanks to pdi33 i got to know dat i haven't used da decouplin capa..gonna try tonight...lets see..thanks again.. :-)
Tue Apr 08 2008, 11:14 pm
#18
in the program dat i used, d 'RET' statement used after second 'ACALL WRITE' is actually for returning frm dis module, so u may giv some name to d lcd module instead of dat 'MAIN' n call it in ur program.
 anee like this.
Wed Apr 09 2008, 10:18 am
#19
IT WORKED!!!!thanks a lot everyone... !dance ...wil be back wid my dac doubts... :-)
Wed Apr 09 2008, 07:23 pm
#20


hi amit,

you are not totally wrong.... so cheer up!!!

there are some applications where tantulum has its advantages over ceramic and others... your friend must have seen the difference by using them around the main power circuit areas..!!!!
but as shashi said @ 0.1uF i practically never used a tant..

practically i prefer them when operating at high frequency above or around 50Mhz..
plus sometimes around the power points (vcc-gnd) but never used as small as 0.1uF cant say why

shyam




No problems Amit......you are partly right though.Tantalums will work better where you use electrolytics like 10uF,100uF etc.But for 100nF or so,it's ceramic always.

sashijoseph



Hey thanks for all the info. Got some serious gyaan on capacitors Dint know they could make so much of a difference! Well my friend was using it b/w Vcc n Gnd at the uC only. And like u guys, the 8052 ppl also suggested him to place it as close to the uC. He used a 10uF though (if am not mistaken...)
But i have used a .1uF tant b/w Vcc n Gnd jst nxt to my uC. is it ok or do u think i must switch to ceramic? Regarding noise, i felt my Gnd was clean...

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