I have recently bought new LCD for arduino and it works fine except that after a while it shows weird characters. It is programmed in a way the its screen should clear any existing message (lcd.clear) before printing any new message. However, It works fine for a while and then LCD freaks out and start showing some weird characters and keep piling them in a row. If I reset arduino then it again works fine for a while and then again shows weird characters.
Any idea pls
Thanks
#code #include <IRremote.h>
#include <LiquidCrystal.h>
int RECV_PIN=11;
IRrecv irrecv(RECV_PIN);
decode_results results;
Also try rewriting your code to get rid of the lcd.clear() statement. Just print your new message right on top of the old one and be sure to pad it with blanks if it is shorter than the original message.
We might be able to give some more definitive help if we saw your code and also if we knew what other devices such as motors, solenoids, relays, etc. were involved.
Don
Edit: Well I see that you have gone back and added your code to your original post. Now go back again and add 'code' tags to make it legible. If you don't know how to do this then you might try looking at this: How to use this forum - please read.
And also (without having seen any code yet), do not write to the screen if there is nothing to update on that screen.
It doesn't make much sense to erase and rewrite the screen with the same data, does it ?
Not writing to the screen needlessly also saves a bit of time.
You will see a time when this kind of things matter.
Millions Thanks to who replied. I actually added a IR remote IR recver. whatever I press on remote , my LCD does print it on screen. Yeah also I read that do not use lcd.clear(). What else can be used to instead of it? O dun want any text disruption. I am attaching my skecth with the attachement. hope that will be help you to understand , and you wud be able to give me better solution,
floresta:
Also try rewriting your code to get rid of the lcd.clear() statement. Just print your new message right on top of the old one and be sure to pad it with blanks if it is shorter than the original message.
We might be able to give some more definitive help if we saw your code and also if we knew what other devices such as motors, solenoids, relays, etc. were involved.
Don
IR remote is involved, I am printing values whatever IR remote transmit as in form of DEC. Thanks mate. Kindly find my sketch and please advise on it
LarryD suggests adding filtering on the LCD power pins.. This means soldering a 10µF capacitor (with the correct polarity) between pins 1 and 2 of the display board itself. People have found these displays surprisingly sensitive to power fluctuations.
You certainly may use lcd.clear(); the alternative is to use lcd.setCursor(). What is important is to ensure you only use it when a new complete display event occurs, which must be no more than once per second, if that. The problem has been people using loops which continuously write to the display. Even a dynamic display such as a tachometer must not be written more than about 8 times per second.
If when the fault occurs, you cannot salvage it other than by resetting the Arduino, it is likely that your code is crashing. This is usually due to using string functions - you really need to avoid these. As always the message is: post your code (using code tags) if you want useful answers!
You can do away with the potentiometer by disconnecting the side which goes to 5V, adjusting it for best contrast, measuring its resistance and substituting a fixed resistor which best approximates that value, which will generally be 1k or less.
Hopefully I will soon add capacitor and try, However Being a new in arduino stuff, I still dont understand how i would replace lcd.clear(). I would request you please change show an example or advise a solution for it.
Also, does capacitor has to be precise in capacitance amount? I got 520uF @25v. Can I use this one? Sorry my background is pure Mechanical not eletrical.
520 uF is a lot larger than the 10 uF that was advised (besides 520 is a somewhat odd value).
You can use it but it will generate a larger dip while powering up, and the dip will last a bit longer.
Pay attention to the polarity, or else your test will end spectacular.
amritss47:
Hopefully I will soon add capacitor and try, However Being a new in Arduino stuff, I still don’t understand how I would replace lcd.clear().
The point was that lcd.clear(); is implicitly performed by lcd.begin(16, 2); so it is quite unnecessary in setup() to start with. lcd.clear(); is comparatively slow, so you should generally avoid it unless for some reason you actually want a totally blank display.
In most cases, you merely want to write something different on the display, so you just set the cursor to where you need to write it, and - write it. The only thing of which you need to be careful, is that what you write anew is sufficient to write over all that you no longer wish to see, so you include the necessary blanks at the end of strings. In the case of writing a number, you figure out how many digits the new value has, and add spaces either before or after to ensure it completely overwrites the old value, that is, writes the same number of digits every time. Writing a string of characters is always faster than lcd.clear().
amritss47:
Also, does capacitor has to be precise in capacitance amount?
Not at all, but a range of 10 to 1 is fine for this purpose, so anything from 4.7µF to 47µF would be OK. 520µF sounds a trifle excessive for the reason MAS3 explained.
You have helped me alot. Finally I got solution of it. I did install aa 1.5uF capacitor to power rail which I think have significant effect. However major problem was in contrast pin(V0). What I did was that I was providing power to contrast pin through arduino using PWM pins. I set it to 110 and so that value remain same , alternatively contrast. But it was a major problem. this pin was causing backlight fluctuations and random characters to appear on screen. I removed this wire and then attached it to a pot and now everything is fixed.
This is a nasty trap caused by some "bright sparks" - in various "instructables" and such - fantasising that there is some benefit in being able to adjust the contrast dynamically. And people not uncommonly confuse the contrast and backlight functions.
The fact is, contrast is "set and forget". The correct contrast value is - the correct contrast value - there is almost never a need to vary it.
In fact, variable backlight brightness is almost never required either; at most you might require three settings - off, dim for night use, and fully on.
But the reason why the ill-fated notion of controlling the contrast voltage with PWM would cause such trouble, is that unless you provide a proper resistor-capacitor filter to smooth the contrast voltage, you are intermodulating the multiplexing signals to the LCD with your PWM and thereby generating quite random patterns.
What is difficult to figure, is how it would work at all to start with.
Oh, and do please go back to your first post and mark up the code properly?
Hopefully I will soon add capacitor and try, However Being a new in arduino stuff, I still dont understand how i would replace lcd.clear(). I would request you please change show an example or advise a solution for it.
Also, does capacitor has to be precise in capacitance amount? I got 520uF @25v. Can I use this one? Sorry my background is pure Mechanical not eletrical.
Thanks
MAS3:
520 uF is a lot larger than the 10 uF that was advised (besides 520 is a somewhat odd value).
You can use it but it will generate a larger dip while powering up, and the dip will last a bit longer.
Pay attention to the polarity, or else your test will end spectacular.
That sugestion worked with me i ised a 100uf capacitor on 1 and 2 pins and the stranger charaters disapeared. Thanks a lot
Paul__B:
This is a nasty trap caused by some "bright sparks" - in various "instructables" and such - fantasising that there is some benefit in being able to adjust the contrast dynamically. And people not uncommonly confuse the contrast and backlight functions.
The fact is, contrast is "set and forget". The correct contrast value is - the correct contrast value - there is almost never a need to vary it.
In fact, variable backlight brightness is almost never required either; at most you might require three settings - off, dim for night use, and fully on.
But the reason why the ill-fated notion of controlling the contrast voltage with PWM would cause such trouble, is that unless you provide a proper resistor-capacitor filter to smooth the contrast voltage, you are intermodulating the multiplexing signals to the LCD with your PWM and thereby generating quite random patterns.
What is difficult to figure, is how it would work at all to start with.
Oh, and do please go back to your first post and mark up the code properly?
Hey, I know I am jumping on an old post, and there are many like it, but I felt as though I needed to respond here.
While it is a little extra work to controll the contrast with a PWM signal, it is worth doing in some applications. For instance, when there is more of a load on the circuit. Many ways to tackle the scenareo, but being able to allow the user, or auto control the contrast is sometimes needed and I think maybe worth explaining. ... but I will save that for a later time maybe.. and focus on the garbage displayed on a screen resolution.
I also wanted to add a bit of experience I have had with LCD's thus far and some of the gotchas I have read in posts on the internet as well.
Gotchas:
Do not clear the screen in a loop, just dont.
Overwriting the entire screen even if just with blank characters is better/faster than clearing.
Use F("my message") strings when possible.
Avoid String types, period.
If you get garbage, be sure to check that if you are printing variable you still hold a valid reference to that variable.
Try not to use long term references.
I2C - be sure to pull up your data lines, especially when there are multiple devices on the bus.
Be sure you have sufficient delays for screen refreshing. It doesnt need to update faster than 250ms honestly to be real time.
Disable interrupts while updating the screen!!! Then re-enable them...
Displaying info is slow, so consider that when you write firmware.
I am fairly certain, if you read and correct the gotchas in the above list, you will stop getting garbage. Worse case, it doesnt work, and thats likely due to a crappy screen, wiring, noise, etc.. which all falls under hardware. FOr the most part all the screens I have encountered are reliable and easy to use as long as you keep the above in mind. Feel free to DM me, or reply here if you need help.
Well, the problem is that using PWM to control contrast requires a lot of extra work extra work since you have to filter the PWM to a reasonable DC and then buffer it with something resembling an op-amp in order to drive it with a low impedance since the usual effective value of the pull-down from pin 3 to ground is less than 470 Ohms and you may want to produce the same effect as a 47 Ohm resistor. You cannot just connect an Arduino output to a 22 Ohm resistor and 100 µF capacitor.
As most I2C backpacks and port expanders include pull-ups, you are often at risk of having too many pull-ups on multiple modules.
You mean to say "It doesn't need to update any more often than 250ms honestly to be real time, and only ever if some data has changed."
m4k3r may be concerned that interrupts could interfere with the I2C but that should not be a problem as you never use interrupts to implement I2C functions.
Similarly, without I2C, the HD44780/ clone does not care a whit about waiting in between steps.
hope you all are kewl,
