Character LCD Vss & Vdd transposed

Go To Last Post
5 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Quite a few years ago I came across a 2X16 LCD where pin1=Vdd & pin2=Vss, when generally they are always pin1=Vss & pin2=Vdd.
It was only one supply of LCD's that was consistantly the same & I avoided using it.

Recently, I came across a recovered LCD which had exactly the right size to be able to fit into a faulty piece of equipment that has a faulty display (Icom IC-R7000).
So I made up the right lead, hooked it up to the MPU on which I have the retrofit code running ....nothing... but a warm Hitachi chip & a hot regulator. I thought I had stuffed up my cable, but alas, checking it with a multimeter it has pin1 & pin2 transposed. Bugger! I will make up another lead with just pin 1 & 2 transposed and hope that it still works!
In retrospect I should have checked! :oops:

A tip to consider when using LCD's without a data sheet.

Edit.
I was lucky. After transposing wire 1 & 2 only on a 2X7 IDC connector, the LCD sprung into life. :)

Charles Darwin, Lord Kelvin & Murphy are always lurking about!
Lee -.-
Riddle me this...How did the serpent move around before the fall?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

AFAIK the LCDs that have the connector on the side (ie Jaycar QP5516 and similar) have the pins transposed, I have a PCB that caters for them

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Spot on John. I used to have students blow up LCD's when they were dicking around with H/W or S/W. The LCD we supplied were the standard type. They would then go down the street to Jaycar and replace them with the QP5516 type, which of course would not help their cause one little bit. Trap for newbies.

Charles Darwin, Lord Kelvin & Murphy are always lurking about!
Lee -.-
Riddle me this...How did the serpent move around before the fall?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Quote:
Trap for newbies.
Actually I had a job where another contractor could not get the LCD working even though it was "wired correctly", standard LCD libraries were used and the LCD worked on his prototype which, of course, used another type of display.

5s I got it working when I got the job to finish off the project (other stuff also). Several pixel were dead, but it worked otherwise, even though the display must have been abused for a long time.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I have seen some LCD die after only 10-15 seconds reversal. Todays reversal would have been about that time as soon as my "nose" & 6th. sense picked the problem up. It looks OK, but I will check it for all pixels.

Charles Darwin, Lord Kelvin & Murphy are always lurking about!
Lee -.-
Riddle me this...How did the serpent move around before the fall?