R20 value for displays

Does anyone know the typical values to use for R20 (68 on circuit board) for the various typical Shruthi displays, red, green, white / blue, etc… I forgot what I used for an NHD-0216K1Z-NSW-BBW-L (white/blue), thought maybe we could have a post with the values. Tried searching.

For the Newhaven stuff: a strap - their current limiting resistor is built-in.

Thanks! That makes it easy.

Me again, parts shopping. What about the Red on Black displays at Sparkfun, LCD-00791, any special resistor value for those?

Where can I find the Green on Black displays used in the SMR4 mkII model that I made from the Mutable kit, and what is that resistor value?


Sparkfun: ask them, because the datasheet they publish is still from their former supplier - but now they have custom boards made at another place. I got my LCDs from Xiamen Ocular (former sparkfun supplier), but their MOQ is 250 pieces.

I recommend the Newhaven parts available at Mouser. They don’t need any current limiting resistor.

This comment amongst the top on said LCD says something about it :
"Running at 5v won’t hurt at all. I have one for several years and the backlight still works."
So, no special resistor seems necessary… (Don’t hang me if it is though)

I remember that the displays from the kits were a custom deal…

when in doubt, stick a 500R pot(rheostat) in place of the resistor and dial it in.

Sort of off-topic but is this display okay for a Shruthi? It seems to match the other suggested Mouser part:



Yes, but I have tried several of these “black on white” displays and they were a bit disappointing…

Thanks Olivier. They look nice in the photos but perhaps I’ll stick with your original recommendation then.

hmm, I worked on a MB6582 that had a transflective 4x20 and it was outstanding. It was either the newhaven or Kyocera/Optrex one

I’m thinking of trying the 18 pin NHD-0216K1Z-FS(RGB)FBW-REV1 RBG display, with some pin rerouting for pins 15-18 and resistors to get the backlight voltages down to 2.2V and 3.3V, and maybe a little switch to select the backlight color, although black on blue was never a good idea (Casio FZ20M).

I bought this screen for my Shruthi build.

Could someone help me choose the right resistor for R20? I’ve never done a build before with a display. Should I buy a few resistor values between 3.3 and 68 and see what works? Or should I try the 500R trimmer? Any other tips? Thanks

I don’t remember having used those, so the best is to try starting from 100 and go down the E6 series 68, 47, 33, 22, 15, 10… until you don’t notice any change.

Thanks for the resistor tip. I’m not sure what is the best way to test the resistor, since the lcd screen will be soldered in place. To test the resistors what is the best technique? Do you solder it in then and if it doesn’t work use solder wick to get it out? I was thinking to use header pins on the pcb and soldering a female header onto the resistor. ?

No need to solder or use a header… just insert the resistor in the holes, and twist the pins so it stays in place and there is a good enough contact.

Thanks for that information, my Shruthi is near completion.

So I did some experimenting and the 68 ohm looked good. Though the display text is a little dim in comparison to the leds which seem alot brighter. I only noticed this after I soldered in the 68 ohm resistor. It was a great learning experience, I used a breadboard with jumper cables for the resistor test and to provide power.

Here’s a picture.