VCC and Ground

Started by Thai November 14, 2009
Hello all,

I just purchased a Minidragon plus2 board and would like to interface it with a 16x2 LCD display but I could not find where VCC and GROUND on the board to power the LCD. Also do I really need a 10K POT to turn on the LCD or is it for contrast control

Thanks

most lcds that i know of either parllel or serial .. i believe there are different methods to interface them.  i prefer serial lcds to parllel though there are serial interfaces with pics placed on them to interface with the parellel ones or make it easier to interface in away.

the pot is most likely for controst control like u said another way to control it with out a pot is using the pwm.

hope this helps in anyway even if a littel .. check out the scematics online for ur minidragon that might show you where the vcc and gnd are

________________________________
From: Thai
To: 6...
Sent: Sat, November 14, 2009 11:18:30 AM
Subject: [68HC12] VCC and Ground

 
Hello all,

I just purchased a Minidragon plus2 board and would like to interface it with a 16x2 LCD display but I could not find where VCC and GROUND on the board to power the LCD. Also do I really need a 10K POT to turn on the LCD or is it for contrast control

Thanks





> Thai writes on 03:18 AM 11/14/2009
>I just purchased a Minidragon plus2 board and would like to
>interface it with a 16x2 LCD display but I could not find where VCC
>and GROUND on the board to power the LCD. Also do I really need a
>10K POT to turn on the LCD or is it for contrast control

Most displays do not need the pot and work find with 0V. Some older
displays that did require it just needed a small negative voltage
which few board have on them without generating it.

Sorry I don't know about the board's power to the LCD.

Bill

The Minidragon plus2 board should have ports/pin already dedicated to the LCD.

As posted earlier, check the schematic...did you purchase the board through wytec?

To: 6...
From: b...@softools.com
Date: Sat, 14 Nov 2009 08:16:07 -0500
Subject: Re: [68HC12] VCC and Ground

> Thai writes on 03:18 AM 11/14/2009
>I just purchased a Minidragon plus2 board and would like to
>interface it with a 16x2 LCD display but I could not find where VCC
>and GROUND on the board to power the LCD. Also do I really need a
>10K POT to turn on the LCD or is it for contrast control

Most displays do not need the pot and work find with 0V. Some older
displays that did require it just needed a small negative voltage
which few board have on them without generating it.

Sorry I don't know about the board's power to the LCD.

Bill

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Yes, I received the minidragon from Wytec, I know there are dedicated pins for LCDs but I would like to connect my LCD on a breadboard directly to port A.

I've connected pin 1 of the LCD(14 pins) to GND of the minidragon and pin 2 to VCC output but the LCD did not turn on so I wonder if the VCC and GND are correct and whether I need a 10K pot.

Thanks you for your help

--- In 6..., justin lucas wrote:
> The Minidragon plus2 board should have ports/pin already dedicated to the LCD.
>
> As posted earlier, check the schematic...did you purchase the board through wytec?
>
>
> To: 6...
> From: bill@...
> Date: Sat, 14 Nov 2009 08:16:07 -0500
> Subject: Re: [68HC12] VCC and Ground
>
>
>
> > Thai writes on 03:18 AM 11/14/2009
> >I just purchased a Minidragon plus2 board and would like to
> >interface it with a 16x2 LCD display but I could not find where VCC
> >and GROUND on the board to power the LCD. Also do I really need a
> >10K POT to turn on the LCD or is it for contrast control
>
> Most displays do not need the pot and work find with 0V. Some older
> displays that did require it just needed a small negative voltage
> which few board have on them without generating it.
>
> Sorry I don't know about the board's power to the LCD.
>
> Bill
>
> _________________________________________________________________
> Windows 7: It works the way you want. Learn more.
> http://www.microsoft.com/Windows/windows-7/default.aspx?ocid=PID24727::T:WLMTAGL:ON:WL:en-US:WWL_WIN_evergreen:112009v2
>
>
>

Standard pinout for a Hitachi 44780 (or compatible) based charcter display does
have GND at pin 1 and VCC at pin 2 so you do have these correct.

However, the third pin is Vee, which is the liquid crystal drive voltage and it
must be connected to get the display to show anything.

On standard LCD's the Vee voltage will have to be between Vcc and 0V and it is
temperature dependent which is why a potentiometer is mostly used. If the
display is always going to be used indoors were the temperature always is
within a narrow range you can use a voltage divider with resistors instead.

If the display is a temperature extended model Vee will have to be negative
(around -5V) and the potentiometer is connected between the negative voltage
and GND. A negative voltage can be created with a pulsed output, a couple of
capacitors and diodes, or, if you have an RS232 driver circuit, you can take
the negative voltage from there. Just make sure to filter it properly and
perhaps separate it with a diode, otherwise the contrast may be fluctuating
because the Vee voltage is changing.

For more information, take a look at this link:



Good luck / Ruben

> Yes, I received the minidragon from Wytec, I know there are dedicated pins for
> LCDs but I would like to connect my LCD on a breadboard directly to port A.
>
> I've connected pin 1 of the LCD(14 pins) to GND of the minidragon and pin 2 to
> VCC output but the LCD did not turn on so I wonder if the VCC and GND are
> correct and whether I need a 10K pot.
>
> Thanks you for your help
=============================Ruben Jsson
AB Liros Electronic
Box 9124, 200 39 Malm Sweden
TEL INT +46 40142078
FAX INT +46 40947388
r...@pp.sbbs.se
=============================
Pending on which version you are using of the board determines what pins can be used. If you are using the Mini-dragon Rev F, then the schematic specifically describes J21 (dedicated PORT for LCD) as pin 1 as GND and Pin 2 as VCC. It would appear you have the two set up correctly, but the other ports should be connected as well...as far as the pot goes...if you use the dedicated port for the LCD then no pot is needed. Not really sure about using PORTA. I recommend using the decidated J21 for the LCD...easier and already configured for output with the configuration for the LCD connection. Is there a requirement to use PORTA?

Good luck

Justin
To: 6...
From: d...@yahoo.com
Date: Sat, 14 Nov 2009 17:41:50 +0000
Subject: [68HC12] Re: VCC and Ground

Yes, I received the minidragon from Wytec, I know there are dedicated pins for LCDs but I would like to connect my LCD on a breadboard directly to port A.

I've connected pin 1 of the LCD(14 pins) to GND of the minidragon and pin 2 to VCC output but the LCD did not turn on so I wonder if the VCC and GND are correct and whether I need a 10K pot.

Thanks you for your help

--- In 6..., justin lucas wrote:
> The Minidragon plus2 board should have ports/pin already dedicated to the LCD.
>
> As posted earlier, check the schematic...did you purchase the board through wytec?
> To: 6...
> From: bill@...
> Date: Sat, 14 Nov 2009 08:16:07 -0500
> Subject: Re: [68HC12] VCC and Ground
>
> > Thai writes on 03:18 AM 11/14/2009
> >I just purchased a Minidragon plus2 board and would like to
> >interface it with a 16x2 LCD display but I could not find where VCC
> >and GROUND on the board to power the LCD. Also do I really need a
> >10K POT to turn on the LCD or is it for contrast control
>
> Most displays do not need the pot and work find with 0V. Some older
> displays that did require it just needed a small negative voltage
> which few board have on them without generating it.
>
> Sorry I don't know about the board's power to the LCD.
>
> Bill
>
> __________________________________________________________
> Windows 7: It works the way you want. Learn more.
> http://www.microsoft.com/Windows/windows-7/default.aspx?ocid=PID24727::T:WLMTAGL:ON:WL:en-US:WWL_WIN_evergreen:112009v2
>
>
>

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