How durable is a HD44780

j m · Post by **j m** » August 5th, 2005, 6:10 pm

Would reversing the polarity cause damage to the controller chip.
I?m having problems getting it to work when I first connected the lcd (2x16 5.5x3mm)
I got the polarity mixed up, it wasn?t connected to the computer and it was for maybe 5-10sec. I quickly corrected this and the back light comes on and I get the top line of full of solid blocks

_X7JAY7X_ · Post by **_X7JAY7X_** » August 5th, 2005, 8:59 pm

Yes, it will wreck it, 9 out of 10 times.

Just because the solid lines appear does not mean the LCD is good. I have one that the lines appear but the LCD is dead, it will not work at all.

I would check the wiring just to make sure that is all good, but it is most likely bad.

J

j m · Post by **j m** » August 6th, 2005, 3:07 pm

Thanks, that?s what I thought. It happened because I using one of those plug-in power supplies where you can change the polarity by swapping the adapter plug round.

I knew that getting the polarity mixed up would damage it and thought that I had double cheeked, but I wanted to get it working and must of missed it. I?ve just ordered a new one and am going to get this one right. This is the link that I was using http://www.icehw.net/article.php?id=104 , this time I think I will put a diode in, so even if the polarity gets mixed up I wont damage it (which is what I thought about when I first saw the circuit diagram) I think that I will use a USB port to power it (would I need a capacitor to smooth the power??) and have the back light controlled. Like this which I just found on this forum (and wish I had found first) http://www.lansley.co.uk/forum/phpBB2/v ... .php?t=187 this also has a resistor for the lcd which looking at data sheet I have is also needed to get it to the 4.5v

This is how I have mounted the screen when I get the new one working I will use double sided tape to fix the screen flat to the case.

Although the case is blue you can still easy see the screen inside
And for the lead I use a old printer one and just cut the printer end off.
Sorry for the long post
Comments encouraged
J m [/img]

_X7JAY7X_ · Post by **_X7JAY7X_** » August 6th, 2005, 5:18 pm

You shouldnt need a cap to smooth the power. The power supply in the computer does an excellent job of filtering/smoothing, but if you want to add one it probably woulndt hurt.

Those connectors are horrible. We have some at work that we use to charge our meters and I am cautious every time I use one.

The purpose of the resistor is not to drop the voltage, but to limit the current. In the datasheet it should give you a current rating on your backlight. There is a formula you can use (ohms law) to figure out the exact resistor, or you can do trial and error. I think I am using a 10 ohm resistor on mine with no problems.

GL

J

j m · Post by **j m** » August 6th, 2005, 11:04 pm

Yes I forget some times what does what, electronics is only a hobby. Looking at the data sheet it only say?s 4.5V(typ.) I missed the typical bit the fist time. What I was thinking off are Zener Diodes and a BZX79C would be 4.3v but as nobody else has any problems without them so I don?t think I will bother
I think I?ll add the capacitor as at moment I will keep using my adapter, until I sort out the USB lead.

I have just done this quickly using egale

I think 220 is probably a bit big and I have already got some 1N4001
jm