LCD will not start

[skimask]

MCLR / Vdd - 5v (if running a 5v power supply, otherwise, take all these reading and divide them down accordingly)

Vss - 0v

OSC1 / OSC2 - with an external oscillator/crystal, somewhere around 2.5v give or take, because the meter is really reading DC, it's catching the average of the DC, which since it's going high/low/high/etc, is around 2.5v.

Pins set to an input will most likely read about 2.5v, or a suitable fraction of the main power supply voltage.

Pins set to output and logic low will be between 0v and about .6v

Pins set to output and logic high will be around 7/10 of the main power voltage.

All interconnects on your breadboard should be practically a dead short, like less than about 10 ohms or so. Don't forget to check your multimeter leads themselves for resistance.

Hopefully this is what you were asking about. Sounds a tad bit basic to me, but that's just me...

By checking the new chip against the old chip alongside it in identical circuits, you are doing what I call a 'signature check', good troubleshooting technique, but it really only works if you've got a couple of known good working setups to verify another bad setup.

[Archangel]

Joes & Ski,
Thank you for the help.

JoeS,
Using an Ohmeter, which pins do I tap, what to expect and why? I would also do the Ohmeter test on a new chip alongside with this chip in question.

Regards,
JohnPaul

Hi JP,
Pretty much as skimask said, just check from the leads of the components to where they are supposed to be connected ( the other component ). These breadboards get really spooky over time. Darrel told me he only uses them once. That's too rich for my blood but my time is perhaps less valuable. Certainly I do not do this for a living. I dissasembled my old breadboards and was very surprised at what I found in the way of wear and corrosion. This is especially important on the VSS & VDD connections so power flows through the device in the way it's designers intended, otherwise very strange current paths can exist and FRY something.
JS

[JohnPaul]

Hey, folks. No progress today... Hehehe... I actually mean I slacked off. I could not find my other 627A. Use of magnifier did not helped. I would try the 84A but have to use OSC chip or I have to use my 40 pins. I could not wait for the weekend to come.

What is the most advanced PIC chip one could wish for? I like my 627A since it has internal OSC.

I am reserving my 40 pins for more complexed project in the future.


Cheers!

John Paul

[JohnPaul]

JohnS,
I bought this regulated variable PS. They go by 1.5, 3, 4.5, 6, 9v, 12v.
No +5v! I like it because it's so portable than those high Amp PS. So I was playing with the PIC with 4.5v and ocassionally switching to 6v. Could I have caused the untimely dead of my PIC?
Later, I retrieve one of my breadboard with a T7805. Just to make sure the LCD and Chip now has the recommended (or was it REQUIRED) voltage?
Hahaha...

Regards,
JohnPaul

[skimask]

JohnS, I bought this regulated variable PS. They go by 1.5, 3, 4.5, 6, 9v, 12v. No +5v! I like it because it's so portable than those high Amp PS. So I was playing with the PIC with 4.5v and ocassionally switching to 6v. Could I have caused the untimely dead of my PIC? Later, I retrieve one of my breadboard with a T7805. Just to make sure the LCD and Chip now has the recommended (or was it REQUIRED) voltage?
Hahaha...
Regards,
JohnPaul

The PIC (and everything else mentioned so far) will run just fine off 4.5v, and the occassional switchover to 6v probably won't hurt it much either. Datasheets say 7V is 'absolute maximum' rating, not recommended for any length of time. I've accidentally ran a couple of my PIC's at 9v before, they still run, not saying they're not damaged and won't fail before the others, but they do still work.

[JohnPaul]

Ski,

I might have pulled the PIC while the power is on. Also, I might have pulled a wire while powered on. I am using a breadboard wire that I like because they are more flexible and easy to insert but I wondered could high current be generated with "loose" connection?
Hehehe... I have done my testimony. Guilty for the dead of my pic? Hahahaha..... I would play with the pic16f84a tonight and catch up with you and Joe.

Regards,
JohnPaul

[skimask]

Ski, I might have pulled the PIC while the power is on. Also, I might have pulled a wire while powered on. I am using a breadboard wire that I like because they are more flexible and easy to insert but I wondered could high current be generated with "loose" connection? Hehehe... I have done my testimony. Guilty for the dead of my pic? Hahahaha..... I would play with the pic16f84a tonight and catch up with you and Joe.
Regards,
JohnPaul

Every 'wire', every circuit trace, everything, is an inductor of sorts, a small one, but an inductor nonetheless. You open a closed circuit, what little magnetic field that had been developed along a specific traces, collapses and induces a voltage (which in turn has a current), and that voltage/current has to go somewhere, usually to ground, sometimes thru a part to ground.
So, I don't think it's the fact that you had 'high current' with that loose connection, I think it would be more to the fact that you might've been jiggling a loose connection causing some really small arcs to occur and putting voltage spikes on whatever wire you were hooked up to.

And there's really nothing wrong with the ol' white, solderless breadboards and those wires that go with them....so long as you realize their limitations as far as frequency and durability go. They don't really like high frequencies, much above about 10Mhz or so because of the parasitic capacitance, causes those nice sharp edges on square waves to get rounded off. And the connections tend to open up and get looser over time.
Keep that in mind while your using those boards, replace them once in awhile, like a few of us around here have started doing, and you'll be alright...
I used to use the large boards, the ones with 3,220 points. I chucked that one and got a handful of the smaller 800 point boards. Much cheaper to replace one of those than the big ones.

[JohnPaul]

Ski,

I see. Make very good sense. Thanks.

Regards,
JohnPaul

[JohnPaul]

Hello, all.

Any advise on PICs for advanced project? I am ordering a few to stack up. Once I get off the ground, I would like doing timer relay project with the LEDs, Security Systems and Stepper Motors. Which PICs are best choices for most advanced... beyond listed above? Also, Is 627A good for beginner like me? I think I would get a couple to stack up. I like it particularly for the internal OSC.

Regards,
Juanito

[JohnPaul]

Hello, all.

Any advise on PICs for advanced project? I am ordering a few to stack up. Once I get off the ground, I would like doing timer relay project with the LEDs, Security Systems and Stepper Motors. Which PICs are best choices for most advanced... beyond listed above? Also, Is 627A good for beginner like me? I think I would get a couple to stack up. I like it particularly for the internal OSC.

Regards,
John Paul ( I should have posted)