need a help with PCB.

[t.man]

Hi t.man,

I've made a new board design using all parts contained in your schematic + an ISP connector.

The +5V connection at Y2 is not quite clear. Is it connected to pin15? Labels are normally placed left or on top of a pin. This one is underneath the pin meaning a dead short since it also is connected to ground. Also the ground connections to Y2 are not clearly recognizable. As I understood (also due to a missing junction) pins12 through 14 are connected to ground.

What frequency does the XTAL have and what kind of diode is used for D1? For the voltage regulator I assumed an 7805, also no value printed in the schematic.

Boncuk

D1 = 1N4007
XTAL= 4MHz
voltage reg= 78L05


sorry for Y2,
actually i was connecting it to suit my needs, i.e for the LC-display....

LCD pins arrangement: 14-13-12-11-10-9-8-7-6-5-4-3-2-1-16-15
with pin 1 as GND and pin 2 as voltage supply and pin 3 contrast adjust.

file attached.

 

[t.man]

PCB layout

it looks compact now. what board dimensions did u use?

 

[silvarblade]

hi boncuk how did you edit his drawing using eagle?cause an eagle template is different!

 

[Boncuk]

hi boncuk how did you edit his drawing using eagle?cause an eagle template is different!

Hi silvarblade,

I'd like to explain it to you, but I'm afraid I make your brain explode.

Now seriously: You can't edit a drawing importing another file format to Eagle. I just printed the original schematic and made it all new using Eagle.

Hans

 

[Boncuk]

D1 = 1N4007
XTAL= 4MHz
voltage reg= 78L05


sorry for Y2,
actually i was connecting it to suit my needs, i.e for the LC-display....

LCD pins arrangement: 14-13-12-11-10-9-8-7-6-5-4-3-2-1-16-15
with pin 1 as GND and pin 2 as voltage supply and pin 3 contrast adjust.

file attached.

Hi t.man,

an 1N4007 is a bit overkill for false polarity protection. It can handle 1,000V.

are you sure you can get a 4MHz XTAL in a mini-package? I've seen these crystals only as 32.768KHz devices in clocks. Normal cyrstal package is HC-18, or the bigger one HC-49.

I strongly recommend to leave the pin arrangement of Y2 in a logical sequence. It is always better to have a few jumps on a single sided board than a smoking display and/or MCU. The additional advantage: You can plug the display directly onto the connector.

Depending on the backlight you use LED/edge or LED/array the 78L05 won't suffice. The LED/array requires 120mA!

Anyway to avoid overheating of an 78L05 I'd stay with the 7805. It doesn't occupy that much space.

Hans

 

[Boncuk]

connector Y2

Hi t.man,

I just checked the schematic and according to your pin arrangement of Y2 it would look like this: (values in paranthesis are true values for normal connections)

14(1), 13(2), 12(3), 11(4), 10(5), 9(6), 8(7), 7(8), 6(9), 5(10), 4(11), 3(12), 2(13), 16(15), 15(16)

To proceed with the layout there is some info required, mainly because there is an obvious error in connecting the LC-display. At least one data line is missing.

Please label all nets in and out of the MCU. This isn't only helpful for proper layout planning, but also useful for trouble shooting.

Make it look similar to this:

 

[mvs sarma]

Hi t.man,

I just checked the schematic and according to your pin arrangement of Y2 it would look like this: (values in paranthesis are true values for normal connections)

14(1), 13(2), 12(3), 11(4), 10(5), 9(6), 8(7), 7(8), 6(9), 5(10), 4(11), 3(12), 2(13), 16(15), 15(16)

To proceed with the layout there is some info required, mainly because there is an obvious error in connecting the LC-display. At least one data line is missing.

Please label all nets in and out of the MCU. This isn't only helpful for proper layout planning, but also useful for trouble shooting.

Make it look similar to this:

I feel the contrast Potentiometer pin1 should be to Vcc and not to Vee , though some people connect a sing le resistor from Vee to ground. In such case the pot is not needed. perhaps the designer should address this aspect.

 

[Boncuk]

I feel the contrast Potentiometer pin1 should be to Vcc and not to Vee , though some people connect a sing le resistor from Vee to ground. In such case the pot is not needed. perhaps the designer should address this aspect.

I don't feel it. I know it.

 

[Boncuk]

better now?

 

[mvs sarma]

better now?

the cross pinning shown is perhaps not correct. I saw and heave these 1602 models. the pins order is shuffled and datasheweet is tallying with what LCD panels I have.
Seceially to mention that pins 1 to 14 are shown right to left and 16 and 15 follow at the right of pin1. If, J6 is the connector meant for this 1602 type , thw wiring order is to follow the datasheet perhaps. if JHD type is used, the connector works straight.

the Contrast mod appeared OK.
i missed an observation that the limiring resistor is conventionally kept on LED+ (pin16) but it is now on 16/ should not matter seriously but might confuse others at the edge connector shown.

You have indicated that "atleast one dataline is missing" which wire Boncuk?

 

[Boncuk]

You have indicated that "atleast one dataline is missing" which wire Boncuk?

Normally LC-Displays are driven in 8-bit or 4-bit mode. Obviously the 4-bit mode is selected. However that requires nets to pins 4(RS), 5(R/W), 6(E) and pins 11 through 14 (D4..D7), besides VCC, VEE and ground + back light connections. Counting the nets there is one missing.

The current limiting resistor is placed into the ground connection because I use it as a jump in my PCB-layout.

Boncuk

 

[mvs sarma]

Normally LC-Displays are driven in 8-bit or 4-bit mode. Obviously the 4-bit mode is selected. However that requires nets to pins 4(RS), 5(R/W), 6(E) and pins 11 through 14 (D4..D7), besides VCC, VEE and ground + back light connections. Counting the nets there is one missing.

The current limiting resistor is placed into the ground connection because I use it as a jump in my PCB-layout.

Boncuk

You may have to consider - back lit as another pin. this the count is complete.

 

[Boncuk]

You may have to consider - back lit as another pin. this the count is complete.

Go ahead and solve the riddle with 'diced pin numbering' and the unlabelled nets.

The LC-control connections are non-standard. Normally the display is connected to port C.

 

[mvs sarma]

Go ahead and solve the riddle with 'diced pin numbering' and the unlabelled nets.

The LC-control connections are non-standard. Normally the display is connected to port C.

There is no riddle and I use this kind of LC displays Boncuk !

 

[Boncuk]

There is no riddle and I use this kind of LC displays Boncuk !

You hopefully use it with the proper sequence of pins!

 

[lqyromeo]

Although i am not the professional PCB designer, but our company specialized in PCB designer, PCB prototype, Circuit card assembly, you could enter into our website-http://www.pcb-assembly.com.tw, and try to contact them, maybe you could get a best answer. Hope you could find the best reply asap.

 

[t.man]

hi Boncuk,

following your layout, i've been able to come up with this:

what can you say?

 

[Boncuk]

I had preferred you come up with a revised schematic having labels at the nets.

The layout looks OK so far with the exception of the "Christmas tree" underneath the ATMEGA16.

There is a more elegant way to route the traces.

Boncuk

 

[lqyromeo]

good suggestion.

Thanks for your sharing. i will follow it.






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