Dual temp LCD display output

[3v0]

I have never needed a pot to set contrast. But the lack of a decoupling capacitor on the PIC power supply is poor design.

It has been a while but I recall that unless the contrast is set you end up with characters you can not see. It could vary with the display. I have been using some less common stuff for a while so I could be wrong.

There is no harm in putting the pot in as setting it in the center.

 

[ericgibbs]

I went ahead and put in two 0.1uf caps for decoupling one for Vin and one for Vout both go to ground. the voltage to the PIC is 5.2v and for the temp sensor I get around 4.2V

here is a picture of the PCB without the LCD connected, the trim pot has not been solder down yet because I don't know should I take out the 5.1K resistor and use the pot or leave that resistor in and put in the pot as well?

Also the tact switch when pressed it's in a on state it's a SPST type but should I be getting some kind of voltage reading on it when I press it? Because I don't

Hi,
Can you post a track view image of the pcb.
If you use a contrast pot, it can be set for the optimum contrast.

I would expect the PIC pin for the switch to show a high level, when the switch is not pressed, about 4 to 5V.

How are you powering the input to the 7805.?

BTW: post your images to the forum, using the 'manage attachments button'.

 

[3v0]

Erick, we must use different LCD's I will just shut up.

 

[ericgibbs]

Erick, we must use different LCD's I will just shut up.

hi,
I use LASCAR LCD's, they use a pot [5K or 10K], this will give a full range of contrast from no pixels visible thru to complete black.
The pot is handy to set the contrast to suit different ambient light conditions.
I see the OP has fitted an multi-turn which is really OTT, a bog standard single turn pot is OK.

Some versions require a +/-Vcon which is a pain, I usually tap into the MAX232's -9V, if available ,
[ref: which can also drive the -Vsup for a OPA.]

 

[1-3-2-4]

Hi,
Can you post a track view image of the pcb.
If you use a contrast pot, it can be set for the optimum contrast.

I would expect the PIC pin for the switch to show a high level, when the switch is not pressed, about 4 to 5V.

How are you powering the input to the 7805.?

BTW: post your images to the forum, using the 'manage attachments button'.

I don't have a track view of the pcb if your asking if I did it with a PC program.. as for the switch it's in a normally off state until it's pressed.

also the 7805 is being powered by a PC power supply with 12V.

I will take out this resistor for the contrast pin for the LCD and solder down this pot for the LCD. The wiper goes to ground and a end of the pot goes to the pin 3 of the LCD right?

 

[1-3-2-4]

I connected the pot and no matter which way you turn it wont dim.. A little puzzled.. I know the PIC is getting power however I don't have a scope or a logic probe.

 

[1-3-2-4]

I also found a connection that was still grounding the pot when connected to ground so I removed it (the pot is already grounded) now when I turn on the display I get no blocks at all! and when I adjust the pot the contrast does not change at all...

The wiper is connected to Pin 2 and Pin 1 is connected to ground and Pin 3 to 5+

 

[ericgibbs]

I also found a connection that was still grounding the pot when connected to ground so I removed it (the pot is already grounded) now when I turn on the display I get no blocks at all! and when I adjust the pot the contrast does not change at all...

The wiper is connected to Pin 2 and Pin 1 is connected to ground and Pin 3 to 5+

One end of the pot goes to +5V the other end to 0V, the wiper of the pot goes to the contrast pin. Look at this image.

I don't have a track view of the pcb if your asking if I did it with a PC program..

Post the PCB image you have on the PC.

Do you have a voltmeter.?

 

[1-3-2-4]

No I said I did NOT do any drawing on the PC what i uploaded with the picture is the schematic that came with this..

how I saw one error I did I connected by mistake a 10K resistor to the D7 data line.. I dont know if that has any effect on the LCD showing any text.. but I removed it and connected to to the backlight like it should be.. still no text and I can't adjust the pot at all.. I tell you the truth one end is connected to the Voltage regulator 5V+ and the wiper is connected to the contrast Pin 3 and the other end of the pot is connected to the Voltage regulator GND.

no matter how many times I turn it (15 turn pot) or which way I turn it I keep getting 4.9V for the contrast pin.

I take it the higher the voltage the more the screens fades?

If I connect the contrast direct to ground I can see 2 rows of blocks but then again it could be saying something but the contrast is too much to read anything...

 

[ericgibbs]

No I said I did NOT do any drawing on the PC what i uploaded with the picture is the schematic that came with this..

how I saw one error I did I connected by mistake a 10K resistor to the D7 data line.. I dont know if that has any effect on the LCD showing any text.. but I removed it and connected to to the backlight like it should be.. still no text and
The dwg says 10R to the backlight.

I can't adjust the pot at all.. I tell you the truth one end is connected to the Voltage regulator 5V+ and the wiper is connected to the contrast Pin 3 and the other end of the pot is connected to the Voltage regulator GND.

no matter how many times I turn it (15 turn pot) or which way I turn it I keep getting 4.9V for the contrast pin.
You have a missing or incorrect connection on the LCD


I take it the higher the voltage the more the screens fades?
It will

If I connect the contrast direct to ground I can see 2 rows of blocks but then again it could be saying something but the contrast is too much to read anything...
It will, this is why the pot is used, so that you can set the best contrast.

hi,

I know you havn't a dwg other than the one that came with the kit, BUT I would like to see how YOU have wired the project.
Take a clear picture of the backside wiring and post it so we can see if there are any mistakes.

 

[1-3-2-4]

sorry I been trying to post this all day yesterday but all I get is a 502 error trying to get to this site.. sometimes I try up to 15 min and I still can't post..

but I found the error I had a 10K resistor by mistake on the Db7 data line.. also the pot is shot and I had someone say the same as I posted the markings on another site the pot was indeed connected right.. so I just took it off and installed the 5.1K resistor again. works fine now..

however not sure if this will post or not.. it's so slow to load if it does.

 

[alvin_wj]

Hey 1-3-2-4,

I'm built this one... But i don't buy the pre-programmed PIC. Could you share with me the hex file from your pre-programmed PIC. Cause mine just like you.
The first row is showing blocks. Second row show nothing.

It's hard to buy something outside from my country. So if you mind, please share that hex file / source code with me.

Thanks.

 

[1-3-2-4]

I'm sorry one of the thing I did on mistake was solder the PIC direct to the PCB instead of putting it in a removable socket.

 

[alvin_wj]

I'm sorry one of the thing I did on mistake was solder the PIC direct to the PCB instead of putting it in a removable socket.

That's okay. Thanks anyway.