MPGuino not timing out / backlight stays on

[thewanderer]

Hi,

I just finished assembling a MPGuino that's using version 0.86 and installed it in my Civic VX. I noticed hours later that the backlight was still on. I tried setting the timeout lower as a test, but it still never turned off.

Everything else including the contrast seems to work fine... Has anyone had this issue? Any suggestions?

Thanks!

[AndrzejM]

Have you been assembling your MPGuino by yourself? Can you dimm the LCD with the middle button? If not there's something wrong with LED power supply.

Give some more details about your build. If you're using Arduino board or single ATmega chip? I'll give you the solution then. But first check if you can dimm your LCD.

[thewanderer]

I built it with an Arduino. It does cycle through brightness levels 0 - 3 (3 is most dim) when I press the middle button. However... after the brightness level text goes off the screen, it appears to re-brighten back to level 0, no matter what option I pick.

[AndrzejM]

I know what's the issue there... You've used PNP transistor instead of NPN transistor to take care of the LCD backlight (or the other way around NPN instead of PNP - depends on the LCD setup). Switch to similar transistor but of different type and your problem will disappear.

Good luck!

[thewanderer]

Hmm, I followed the circuit here http://ecomodder.com/wiki/images/7/7..._Schematic.GIF that shows a PNP (2N3906) although I used a 2N4403 (somewhat equivalent, also PNP) as it was what I had on hand. Is there a version that uses an NPN instead? I'm using a blue w/ white letter 16x2 standard HD44780 LCD if that makes any difference.

[AndrzejM]

I see... But change it to this:


And it'll solve your issue.

[thewanderer]

Ok, I swapped it out for an NPN and now brightness 0 is off and 3 is brightest. And it stays the brightness level I pick. I'll hook it back up tomorrow to double check it's working in the car, but the brightness seems to be working properly now.

Thanks for your help!!

[AndrzejM]

I'm glad I could be of help

[firehawk618]

Originally Posted by thewanderer

Ok, I swapped it out for an NPN and now brightness 0 is off and 3 is brightest. And it stays the brightness level I pick. I'll hook it back up tomorrow to double check it's working in the car, but the brightness seems to be working properly now.

Thanks for your help!!

So, did this fix your display never turning off?

I am having the exact same issue.

Thanks.

[thewanderer]

Originally Posted by firehawk618

So, did this fix your display never turning off?

I am having the exact same issue.

Thanks.

Yes; switching the transistor fixed this issue for me. Thanks again to AndrzejM for the suggestion!

Now I just have to sort out why the MPG is off