Skip to main content
Topic: Nokia LCD Breakout Board for uC interface by easy components (Read 43106 times) previous topic - next topic

Nokia LCD Breakout Board for uC interface by easy components

Info:
This project is about making an cheap Nokia LCD breakout board for uC interface. The Board will be having a switch to easily switch between 5V logic and 3.3V logic. With internal LCD backlight voltage booster, the product will become something like http://www.sparkfun.com/products/8600 but obviously my target is to make it under 5-6$(LCD included).
History:
A few weeks ago, I was trying to interface a Nokia GLCD into my development board.
I chosen Nokia LCD as they were the most easily available ones and obviously cheap. In my area, a 16x2 character LCD costs 150 INR and a Nokia color LCD(of basic phones) also costs the same. I have chosen the Nokia 2600 LCD for my project.
Info: Nokia 2600 lcd has the same pinout as popular Nokia 6100.
As I was working with a 5V logic uC (Mega32), I has attached a simple resistor based voltage divider circuit to provide 3.3V to the LCD pins. As the following image describes, [attachment=1] the backlight LED supply was connected to a separate header pin and was supplied the 7Volts using external power supply. To solder that on a veroboard, I removed the LCD connector and soldered 42swg enameled copper wires there. A PCB version of this would include a onboard LCD socket so that we van plug-in the LCD modules easily, and will have own voltage booster that will boost the voltage from the LCD supply(3V3 or 5V0 to 7V0).
Plans for final board:
1.A minimal sized board, that is just 5cmx3.5cm.
2. Board will provide pads for comparatively large SMD components like 1206 so that everybody can solder them with normal equipments.
3. There will be a switch for switching between usage in 5V uC or 3V3 uC.
4. The voltage booster circuit will have two or more parallel circuits space, so that the user can easily use available components.
Plans for the inbuilt voltage booster part:
There will be atleast two topologies in the same board so that anyone can be built as per the user's demand.
Plan1: One 555 timer IC based astable pulse generator which saturate/desaturate a G.P BJT and will boost the voltage by an suitable inductor and limit the voltage by a zener diode.
Plan2: One low cost step-up switching regulator of very budgetary price which can accept voltages from 3to5 and can boost to 7volts for the backlight.

A planned view if the final product : [attachment=0]

Advantages of the mentioned LCD:
1. Uses 4pins of uC while generally used HD44780 based LCDs requires atleast 7pins of uC (6 if we neglect the RW pin)
2. Can display more information including graphics.
Disadvantages of the mentioned LCD:
1. Texts are less readable and size is small.
2. Requires atleast 1K coding to display characters. We have to define the characterset and fonts manually.

I need your comments, and suggestions regarding any area of this design before finalizing the product.
Please post your opinions and suggestions below.
Still learning
-Arup

Re: Nokia LCD Breakout Board for uC interface by easy cpmpon

Reply #1
[quote author="MickM"]Hello, very nice project.
Why are the pins 1mm pitch?
If you made them 2.54mm (0.1") then it would plug into a standard breadboard.
Even better would be 90 deg 0.1" pins, then it could lay flat.
MickM[/quote]
The pitch of the pins (metal part) is 1mm. the pin header is cut from standard Berg strip 1X40 Male 10MM (0.1 INCH PITCH) .
Still learning
-Arup

Re: Nokia LCD Breakout Board for uC interface by easy compon

Reply #2
Nice writeup, and great work dead-bug wiring the LCD connector! Beautiful prototyping work.
Got a question? Please ask in the forum for the fastest answers.

Re: Nokia LCD Breakout Board for uC interface by easy compon

Reply #3
UPDATE
First complete PCB Prototype update: I name it v0a.
Details:
1. Uses 10K-4.7K resistor series as voltage divider and the grounding of the signal and voltage pin is through a switch which will allow to select 3.3V logic or 5V logic.
2. There are IN4148 diodes in between the series resistor voltage divider network, so that when the adapter is in 3.3V mode (sw1 off) then no voltage goes through one pin to another via the incomplete resistor divider network.
3. General purpose NE555 (DIP) IC is used as 50% D.C pulse generator. The R,C is so chosen that it gives 100Khz output and the output is then used to switch a general purpose NPN BJT and it boosts the voltage for the backlight by a 470uH inductor coil. Output voltage is limited to 6.8V by the use of a zener diode. A 0.1mfd capacitor is used for stability.

Attached files: [attachment=1][attachment=0]

Since I was designing in Eagle, not in any software that can check logic errors, there may be small mistakes here and there in connection, placement and routing. Please check the schematics carefully before proceeding.
Still learning
-Arup

Re: Nokia LCD Breakout Board for uC interface by easy compon

Reply #4
Update v0b
Fixed:
1. Zener diode polarity
2. Re routed the lcd connector connections
[attachment=1][attachment=0]
Thanks MickM
Still learning
-Arup

UPDATE v1

Reply #5
Finally, after a lots of help from Ian, here's a final board version 1 of the project ready.
Updates:
1. Similar components are placed in group for better look
2. Voltage booster part is in a side of LCD so that's easy to replace.
3. Beneath LCD, there is few small and SMD parts, so you can stick the LCD there with the help of a both sided foam tape.
4. LCD connector Pad has less complexity, you can solder a socket and insert LCD plug there, or else you can remove the LCD connector from the LCD and solder the flexible PCB to the board itself like a BGA Soldering.
5. The switch is on a side with pads and no components nearby, you can replace the switch with any one that fits there.
6. You can replace the boost converter's transistor to a DIP BC548 or similar one. There's enough room in nearby place.
[attachment=0]
Still learning
-Arup

Re: Nokia LCD Breakout Board for uC interface by easy compon

Reply #6
Nice work.

just one hint about the pcb

mounting holes

It would be cool to have mounting holes (in 4 corners for e.g.) on the board so that you can actually mount it with screws instead of gluing it in place. Especially if you are going to attach a screen to this board, you want to be able to affix it to a box so screw holes should go in the area not covered by the screen.

Re: Nokia LCD Breakout Board for uC interface by easy compon

Reply #7
Yes, that is a problem we had in the one on sale now.

Be sure to consider trace width. The traces from 555 and transistor to the inductor should be short and fat. Those look far too thinng to me. You should also consider a ground plane - draw a polygon and name it GND.
Got a question? Please ask in the forum for the fastest answers.

Re: Nokia LCD Breakout Board for uC interface by easy compon

Reply #8
[quote author="ian"] You should also consider a ground plane - draw a polygon and name it GND.[/quote]
I have already did that. I added GND polygon in both side and also ratsneted that. But when I open the file, I see the ratsnest is not saved by some reason.
Still learning
-Arup

Re: Nokia LCD Breakout Board for uC interface by easy compon

Reply #9
[quote author="arupbsk"][quote author="ian"] You should also consider a ground plane - draw a polygon and name it GND.[/quote]
I have already did that. I added GND polygon in both side and also ratsneted that. But when I open the file, I see the ratsnest is not saved by some reason.[/quote]

when you first open a file in eagle, the gnd plane won't be filled in until you use the ratsnest command - then it will "pour" copper onto the plane.  you should still see the dotted line that defines the polygon, though. this actually winds up being quite helpful in some cases when you're routing new traces.

Re: Nokia LCD Breakout Board for uC interface by easy compon

Reply #10
Sorry for a mistake in part name. The 555 IC is used as astable multivibrator to generate 100khz pulses, but there in design I wrote NE555. But NE555 works in 5V and not in 3.3V. The actual part would be TLC555 which is a CMOS version and can run from 2V to 15V.
The NE555 IC is TTL version and if the user works only in 5V mode, then NE555 can be used without any problem.
Still learning
-Arup

Re: Nokia LCD Breakout Board for uC interface by easy compon

Reply #11
I've made a similar breakout board but used discrete components for the backlight boost converter. It uses less components than the 555 based approach http://www.circuitschematicdiagram.com/ ... ransistor/. A word of caution though - as with all open loop voltage boosters be careful of high voltages on the output. The current is low, so its unlikely to shock you, but if you disconnect your LCD (like I do during testing), and then reconnect it to the board, you may fry the LEDs or other electronics on the LCD.

The circuit is excellent and works down to 0.6V. It requires about 0.9V to start. I've got efficiencies of 80% using high gain transistors.
Cheers!
Rohit

Re: Nokia LCD Breakout Board for uC interface by easy compon

Reply #12
Arup,

Here's another way to drive the backlight....I don't know if you've frozen your design yet.....

The previous poster suggested a 2 transistor boost circuit. It looks nice.

Another way is to use a MAX232 chip, which takes 3.3V/5V and pumps it up to 8V or so. The Nokia backlight will drop that to 6.5V, but it's current limited, which is perfect to drive the backlight. You can modify the pump capacitors to vary the current available, and thereby adjust the brightness (I use 10nF/10uF)

I've build 30 boards of my project using this technique, and it's working well. Just a word of warning though....I bought my MAX232 chips from eBay, and I must have gotten some poor devices, because most of them will latchup and draw a hundred mA from the rail. The fix for this is a diode from pin 16 (anode) to pin 2 (cathode), which bootstraps the +6.8V rail up, and prevents latchup.

So the total parts count is 1 MAX232 + 4 caps + 1 diode ($0.30 + $0.04 + $0.05 ~= $0.40).

Good luck with your project.

PatB

Re: Nokia LCD Breakout Board for uC interface by easy compon

Reply #13
Nice rohit, but with 555 based approach, we can have full control over the boosting circuit's frequency and other ratings. We can alter the output as per requirement by replacing resistors and inductors and diodes.

Hi patb, Welcome to the forum.
Nice idea, MAX232 has output voltage as 7V from data lines, and 8.5V from booster section. But the problem with MAX 232 is that it works from 4.5 to 5.5 volts only, and in the case of this board, there is selectable 3V3 and 5V0 logic, so our booster part should work between 3V and 5V range.
If we look for alternative RS232 transreceivers at low voltages, then ADM3312E comes in 2.7V operation, but that will burn in 5V. If you can find a RS232 transreceiver which works between Vcc 3.0V and 5.5V then it would be appreciated.

EDIT: LT1331 is a RS232 transreceiver which can work both in 3.3V and 5V but output voltage is respectively 5.5V and 8.6V.
Still learning
-Arup

Re: Nokia LCD Breakout Board for uC interface by easy compon

Reply #14
Thanks PatB,

Really good idea. I had considered tapping max232 for +/-8 in other projects, but I didn't know it could put out that much current.
Got a question? Please ask in the forum for the fastest answers.