LCD do display - but pins check out

[Tabsoft]

Thanks, I can read this one.
Since you had issues with the LCD before, can you give us the model number?
Really do not want to guess.

[Scampy]

Thanks, I can read this one.
Since you had issues with the LCD before, can you give us the model number?
Really do not want to guess.

The only info I have is what's stamped on the back. RT204-1 (ver2.0) - uses the standard Hitachi HD44780 chipset. Closest datasheet is http://www.satistronics.com/myfiles/...CD/RT204-1.pdf

[andybarrett1]

Hi

Looking at the circuit all looks OK for me. LSB's grounded on display, good !... For me I would have decoupled (0.1uf) around all the chips including the display. I also would have used a trimmer across 5v and 0v (5k) on the contrast (Pin 3)so as I could meddle !!

Nothing wrong in checking all connections are right way around on the board D4-D7 also RS and E, so easy to assume... "I know" I have been burned so many times.

Could be worth checking the Xtal.... Maybe just try switching to internal clock (4Megs), I have had strange things happen around crystal circuits and displays, Some of the EBay types certainly :-) .... Not just with PIC's but other Micros also.

One last thing make sure you protect your AC SSR outputs ... I love MOV's ...At least do fuse them. Good practice to fuse the the low voltage AC before the bridge also.

Hope some of this helps

Andy

[andybarrett1]

Trimmer across 5v and 0v (5k) on the contrast (Pin 3)

Just noticed Pin3 LCD Vo is up high... Should be more Low (0v) if no trimmer ?

[Scampy]

Thanks for the suggestions. I will look at adding a trim pot for the contrast, and a few more decoupling caps in the mix.

Yes, I'll be fitting some chassis mounted fuse holders, or some of those C-13 type sockets with fuse built in to protect the heaters. I also slot the board under the SSR between the low voltage pins and AC pins as a safety feature too.

[Art]

[Scampy]

Just measured the resistance across the 10K pot on the EasyPic5 board. Between Vco and GND pins on the LCD connector I have 5.67K, with 3.12K between Vcc and Vco. I'll amend the schematic and put a 4.7K between GND and Vco

[Scampy]

OK - those ruddy gremlins must of been messing me about yesterday..

I disconnected the resistor on Vco and grounded the pin as it was in the original board design. Connected the LCD and powered up and got two lines of blocks which was something I never got previously and I had tried taking Vco both high and low !

Placed the PIC in the board and booted the board - bingo text displayed...

I'm at a loss as to why, what or how the thing failed to work previously - Oh the jpys of electronics !!!