HD44780 Module

The shop page mentions that a resistor 0Ohm is in line with the GND and V0 (pin 3) and that it can be replaced with an appropriate resistor to adjust contrast. Well guess what, I’ve got an inverted backlit LCD display that is nearly impossible to read at no adjustment. Can someone point me to the correct resistor to unsolder? I don’t see any datasheet as mentioned on the shop page either. A link to that would be best. Thanks in advance.

We are adding tutorials for every single module, see support page. I will ask the guy to give this one priority.

Thanks Gus. I just need the schematic and I can do the tutorial (at least what to do) myself. I’d get glad to help out, I just can’t seem to find the source needed to make it happen. I suppose a volt-ohm-meter across the resistors would do it. I’m just in my office ATM and not in the lab.

even better, will get you schematic on Monday.

It might have to wait till Tuesday as Monday is a holiday. :slight_smile:

I’ve got Tuesday off, so that works for me.

Is there any concept for storing build videos? I suppose I could link them through YouTube or Vimeo.

you can share videos on codeshare, on here or on wiki.

any luck with the schematic?

If you need to change resistor for adjusting contrast, you need to desolder R2 (0ohm) and change the value. I’ve some LCD 4x20 that need around 680-800ohm resistor for good contrast. I can’t remind the correct name of this LDC display … but I think it’s STN blue type.

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thanks for the tip. I’ve got two different ones. One of them is blue the other has no backlight. It would be nice if the board had a trim pot on it but I doubt I could graft one in where R2 is located.

@ jr57k - To make some test for correct resistor, I suggest to desolder R2, then use normal TH resistor between GND and V0 on the LCD connector. When you got the correct one then you solder the smd resistor. Pot is a problem, really…

I don’t have any SMD resistors, I’ll have to get that bit figured out.

@ jr57k -
If you have some through hole resistors, you can solder directly under the V0 and GND pin on the connector on the HD44780 board. Only when you get correct value for your LCD eventually solder on R2 an SMD. I’ve tried a pot on these pins, but not practical …

2.2k resistor is right on the money when using these LCDs from sparkfun;

I just did what was suggested and soldered it right to GND and V0 pin. Works like a charm.