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HP3548 / HP3457 OLED display

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Xyphro:
Hi Guys (and Girls),

I have since quite some time a HP3457 multimeter and hate the display. Had to do something about it. The typical LED Backlight mod was not resonating - it looked still very bad - low contrast.

I had to come up with something else. I loved this idea here from Xi: https://www.eevblog.com/forum/projects/led-display-for-hp-3457a-multimeter-i-did-it-)/50/

But mechanical wise it is very hard to reproduce for others (including me).

After many weeks of hunting for OLED screens in the right format I had a brilliant Idea: Why not use the typical small OLEDs that you can get for extremly low price on Aliexpress and use a single display per digit?! Immediately routed a PCB and ordered it and after some months I had time to take this up and program the SW (thanks again Xi for your groundwork in decoding the protocol!).

The current consumption is extremly low, while the display is very bright: only 20mA are consumed.
Instead of isolating the power supply, I isolated the datapath, so it can still be powered from an AC supply in an galvanically isolated way.

The PCB is from JLCPCB. No milling required and a second PCB (which is not shown) acts as a mechanical holder which has mounting holes and can be mounted without any modification of the multimeter. Also the original flatband cable connector can be used.

Work is nearly done. I think I will put everything together tomorrow and share the final pictures :-)

Best regards,

Kai

Edit: Here a very bad quality video of the current state: https://youtu.be/hoUbkyWuI_g

EHT:
Looking great! I'd seen the backlight mods but didn't fancy the risk of cracking the display open, and then ending up with poor contrast anyway. A new module mechanically compatible with the LCD is perfect!

free_electron:
coooooooool !

Xyphro:
Have built it in and I am very pleased with the result.
Now I have to finish the annuciators (small triangles on the bottom of the screen).

Xyphro:
Some more Photos...

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