[Khalid]

Hi Steve,
My 7805 failed one of BC337 to buzzer was blown away.. I just want to know whether the PIC damaged or not? Any idea?

[kwackers]

Sorry Khalid, I've no idea. (Although the 337 exploding doesn't sound good...) (You may also want to check the LCD.)

A lot depends on how the 7805 failed. I've never known one fail short circuit they've always failed open and so no damage. They have thermal shutdown circuitry to protect them.

Is the input to it fairly high? Maximum is 35v although this would drop 30v across the device which if we assume about 100mA is still 3W dissipation - which is a lot without a good heatsink.
If you're using a high input voltage I'd suggest either another device before the 7805 to drop the voltage (this can be offboard and bolted to a heatsink) or a separate supply (say 8-12v) to power the unit independently.

Good luck - hope it hasn't fried anything.

[Khalid]

Hi steve, the 7805 is fed with 22V ....The LCD backlit leds are working and two/three strange vertical lines are also displayed on LCD...
I am afraid i have fried the PIC, any means to check the PIC?

I ahve an expensive PIC programmer on hand (QL-2006):
QL2006 USB & RS232 PIC Programmer for Microchip MCU

i want to program a new PIC452 with it..what initial settings i should use?The PIC is not bootloaded..need help please.

[kwackers]

Should be fine on 22v. That's about what I run mine on, I do have a reasonable heatsink though. When it's working again check how hot it gets, as a rule of thumb if something gets too hot to hold for a short amount of time - then I stick an heatsink on it :0)

If you load the HEX file into your programmer software you shouldn't need to set up anything - it should just work. All the settings are contained within the hex file itself.

If the PIC has been fried then I'm afraid imo the LCD will have died too...

[Khalid]

Thanks Steve...I have to built the complete unit again...I think someone here posted the wide-traces PCB files...

Have just to search this thread or if someone help me point out workable PCB sketch with wide and clear traces so that etching possible without any loose or connected traces..PS:
I found the LCD backlight LED's are working...i hope the LCD not damage..

[Bravo]

Thanks Steve...I have to built the complete unit again...I think someone here posted the wide-traces PCB files...

Have just to search this thread or if someone help me point out workable PCB sketch with wide and clear traces so that etching possible without any loose or connected traces..PS:
I found the LCD backlight LED's are working...i hope the LCD not damage..

Hi Khalid,

On page 29 post No. 347 Lucas posted the copper and silkscreen pdf of a PCB with wider tracks. This is his corrected version. There is some pictures of the built PCB on the next 2 pages.

It looks quite good to me but I would like it with wider solder pads.

I had been looking at it myself as I melted some of the small round solder pads when I soldered the resistors on Kwackers PCB.

I hope this is what you require.

Regards,
Bravo.

[Khalid]

Hi Bravo, Thank you for pointing out and confirming the correct workable PCB with wide-tracks and thanks to Lucas too for taking time and posting his PCB...
My Question will be, the dimensions of Steve and Lucas PCB.. as it is very important for me because i have to replace the Steve PCB with Lucas PCB on the existing box..

[Khalid]

Almost completed the 2nd Board the same as Lucas did in page 29. Lucas or anybody else can tell me why the Backlight resistor required and what is the value of that resistor?
Regards

[lucas]

The value depends on the LCD you use.

Most LCD's have a led array wich needs something like 4.2V and the current depends on the type of LCD.
So you need a resistor to drop the 5V to the backlight value for the given current.
In my case it was 4.2V @ 260mA, the math results in 3 ohm.

But that 260mA also passes through the 7805, if you use 24V then the 7805 has to dissipate an additional 5W so it will need a very large heatsink.

This is why I experimented and tried a 56 ohm resistor, the backlight current is reduced and the LCD readability is good enough.

Do you have the spec's of your LCD?

Note that some LCD's have that resistor already installed and thus work on 5V.

Luc.

[Khalid]

Do you have the spec's of your LCD?

Note that some LCD's have that resistor already installed and thus work on 5V.

Luc.

Hi Luc.. thanks for the detail reply and calculation. Following is the spec sheet of the LCD i am using:
Welcome to Kingsun United Development Co., Ltd.
http://www.topwaydisplay.com/Pub/Man...ual-Rev0.1.pdf

[Khalid]

Onething more to ask.. The Backlight resistor is installed on 5V output of 7805 IC?? So why to give 22V or 24VDC? your resistor seems to me of 1/2watt or 3/4watt as its too fat as compared to others resistors..

[lucas]

Reason for the fatter resistor: didn't have a smaller one.

The entire unit runs on 5V, thus also the backlight.
IC 7805 regulates the external supply to that 5V and must dissipate the excess power, with your display and the 22V input supply you are using it will also be around 5 Watt. So a decent heatsink on the 7805 is needed.

Your display has the resistor included so you can use a jumper wire to feed the 5V to it. If it doen't have to be real bright then you could use a low value resistor.

BTW: What did you use before? Is this still the same LCD?
If it is, then it should work as your original unit before it broke down.

[Khalid]

Hi Steve,
This is my first time programming of PIC.. i do not know much about..I uploaded your Firmware V2.1 in QL-2006 software and here in attached pictures you will find some parameters..
Are these okay or need any changes.. Dont forget i am using your V2.1 firmware.

[Khalid]

Thanks Steve and Lucas.. My second PCB work fine now.. I have reduced the input volts to 7805 about 9VDC...

[Khalid]

I have developed 4x4 Keypad for big buttons.. Is their anybody who can verify or correction?
Regards

[Khalid]

Finished untested board:

Attach is the PDF file for etching.

[Khalid]

tested the keypad and its working perfect...

[kwackers]

Apologies if someone was expecting a reply from me... After a brief respite I've stopped getting "new-post" alerts...

[kwackers]

Updated manual and new HEX file

Attached to his post is an updated manual with the missing options in setup I added a while ago put in.

Also a new HEX file. This file has NO extra functionality so is of no interest to most - but it DOES (in theory) work with the 18F4520, the same HEX file should also be capable of being used on a 18F452 - although I should point out I've run out of spare 452's and so haven't tested it...

If there are any problems let me know...


(Thanks to Marty and Lee for taking the time to figure out why the code didn't work properly on the 4520.)

(Just spotted, in the manual I've missed out saying you can zero position etc in any mode by pressing the zero [0] key...)

[marzetti]

Khalid- Your keypad looks great. What sort of overlay will you use over the keys?