Can I do this with a uProcessor?

[Eeyore]

just

Right, that was going to be my next question. I've looked at the parts that
have been mentioned here, but I've got to find someone who will ship to
Canada without a ridiculous minimum order. Newark has the Atmel IC listed,
but it isn't in stock atm, and has a 99 day lead time (!?). Mouser doesn't
appear to have anything, and DigiKey, well - there's that minimum order
problem again.

Well..... Atmel has a 'buy from from distribution' link on their site and Arrow
will certainly deliver to Canada but you'd have to check out the cost.

Then again there's ebay ! The 89C52 should do the job IIRC.
http://cgi.ebay.com/5-x-ATMEL-89C52...2QQihZ013QQcategoryZ50915QQrdZ1QQcmdZViewItem

5 of them for $18 !

But then again there's this !

http://cgi.ebay.com/Burner-Free-805...1QQihZ015QQcategoryZ50915QQrdZ1QQcmdZViewItem

It looks perfect for your needs. I'd ask if they can supply a suitable chip
althoiugh if it'll program the Philips 89C51, I'd expect it to do the above
Atmel 89C52 as well

I also found this http://www.hvwtech.com/products_view.asp?ProductID=370
which i can get here, but don't know much about PICs

I can't help you there either.

Graham

 

[Spehro Pefhany]

Latchup is a serious issue, especially with some Analog Devices ics
where they fail to warn you the chip is sensitive and will die, like
some of their DDS chips. So now I use a buffer like a 74LS04 or
2N2222 inverter between the chip and the outside world.

Connecting a CMOS IC pin directly the outside world is pretty much
inviting trouble to your doorstep, IME. There's really no reliable
spec AFAIK, but parts with robust output drive seem to do better than
parts with wimpy output drive.

ESD is a big problem, even with parts that are rated for body or
machine discharge. You can always find a discharge that is larger.
For example, walking across a carpet in Colorado in the winter can
easily generate 1 inch sparks.

The voltage is high enough, so wouldn't it simply arc over a small
smd part? What kind of resistor would solve that problem?

Yes it would, but if it arcs from A to B (where B is not an IC pin)
and then you have a series impedance to the pin from A, you've limited
the current and the energy. It's like lightning, you can't stop it
from happening, and you can't control the amount of energy, but you
can hopefully force it to take an alternate path and prevent damage
when it does take that path, at least up to a reasonable energy level.

Most of the stuff you do to make the micro immune to RF and ESD also
works to reduce the noise emitted by the circuit.


Best regards,
Spehro Pefhany

 

[Mike Monett]

[...]

Yes it would, but if it arcs from A to B (where B is not an IC pin)
and then you have a series impedance to the pin from A, you've limited
the current and the energy. It's like lightning, you can't stop it
from happening, and you can't control the amount of energy, but you
can hopefully force it to take an alternate path and prevent damage
when it does take that path, at least up to a reasonable energy level.

Most of the stuff you do to make the micro immune to RF and ESD also
works to reduce the noise emitted by the circuit.

Best regards,
Spehro Pefhany

Well, if you can get it to survive a Colorado winter, my hat's off to you

Regards,

Mike Monett

 

[Spehro Pefhany]

[...]

Yes it would, but if it arcs from A to B (where B is not an IC pin)
and then you have a series impedance to the pin from A, you've limited
the current and the energy. It's like lightning, you can't stop it
from happening, and you can't control the amount of energy, but you
can hopefully force it to take an alternate path and prevent damage
when it does take that path, at least up to a reasonable energy level.

Most of the stuff you do to make the micro immune to RF and ESD also
works to reduce the noise emitted by the circuit.

Best regards,
Spehro Pefhany

Well, if you can get it to survive a Colorado winter, my hat's off to you

Regards,

Mike Monett

Florida summers are pretty bad too, for different reasons.


Best regards,
Spehro Pefhany

 

[Rich Grise]

My own first expereinces with 8051 were also wire-wrapped ! We got some of the
very first examples of the real 80C31 MCU in CMOS too. That helped a fair bit
with our power budget.

I still have my WSU-30M - I used to wire-wrap stuff all the time.

In 1980! ;-)

Can you still even get wire-wrap sockets?

Cheers!
Rich

 

[Mike Monett]

Florida summers are pretty bad too, for different reasons.

I had to take my Malibu back to Piper in Boca Raton several times for
maintenance. The thunderstorms and humidity were quite impressive!

I used to smoke then. I would go out on a back balcony to enjoy the view of
a small pond lined with trees.

One night I noticed a pair of eyes staring back at me. They belonged to the
biggest alligator I have ever seen. I know how fast they can run, and I
don't mind saying that frightened the daylights out of me.

Then I discovered the door had closed and locked, and there was no way to
get back in.

Fortunately, a waitress decided at that moment to take a smoke break, and
came out on the balcony. I showed her the alligator, but she didn't mind.
She knew all about him. But that was the end of smoke breaks for me

Is that what you were referring to?

Best regards,
Spehro Pefhany

Regards,

Mike Monett

 

[krw]

Wire wrap? Are you H.G.Wells, or what? ;-)

Wire Wrap at these frequencies is a piece of cake. I've done it
*many* times. I used WW once at 80MHz with MECL-10K, but I wouldn't
recommend making a habit out of it. ;-)

 

[MooseFET]

On May 24, 8:02 am, Eeyore <[email protected]>
wrote:
[....]

There's no practical path for ESD between say a TACT type switch with its mounded on keytop

On the membrane keypad, you can mount it on aluminum and have a ground
foil layer in front of the actual switch.

[....]

and the internal circuitry. If someone's sufficiently charged with statis for it find a apth,
a little ressitor isn't going to save anything !

The resistor will survive just fine. It is protected by the micro.

 

[MooseFET]

Wire wrap? Are you H.G.Wells, or what? ;-)

He was a drunk.

 

[Eeyore]

On May 24, 8:02 am, Eeyore <[email protected]>
wrote:
[....]

There's no practical path for ESD between say a TACT type switch with its mounded on keytop

On the membrane keypad, you can mount it on aluminum and have a ground
foil layer in front of the actual switch.

[....]

and the internal circuitry. If someone's sufficiently charged with statis for it find a apth,
a little ressitor isn't going to save anything !

The resistor will survive just fine. It is protected by the micro.

Exactly !

I had great fun in the early days of getting used to EMC, making my own EHT supply at about 8kV
that I used some for empirical static susceptibility tests.

Graham

 

[mpm]

That's an AVR. It's an Atmel specific design AIUI. A different architecture entirely from an 8051 family
part.

Not to mention the words "Preliminary Data Sheet" practically jump off
the page.
I think AVR is overkill. It's a guitar, not a missle silo.

TF, an 8051, or a derivative like the Atmel 89S8253 seems ideal for
your project!
Since this is your first design, I would recommend you NOT try your
hand at keyboard scanning just yet. It's not complicated, but your
project doesn't require it.

The bueaty is, you actually have enough pins on the 8253 to do it both
ways, if you are, (or think you might get) worked up about keyboard
scanning. But again, why complicate things??

Obligatory Note: Early datasheets on the 8253 had a major error
relating to crystal caps needed to guarantee stratup. (specifying
33pF, when more like 5pF, or even 0pf was more in order.) This is
corrected in the current datasheets on the Atmel site.

The oscillator in the 8253 is different from the 8252. (I forgot to
mention that in my earlier post).
Better, in my opinion, as below about 12MHz, you can ditch the caps
from the build list and save a few more pennies. Plus, it has
internal reset, when a lot of the other 8051 stuff out there requires
a RC network. Saves a few more pennies, but Pin-9 (on a 40-pin DIP
pkg) is still there if you want to roll your own reset circuit.

-mpm

 

[mpm]

Wiring switches directly to I/O ports is a really bad idea. At least
put some series resistance in there. Then you have to consider the
3:1~10:1 range of typical pull-up current sources.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
[email protected] Info for manufacturers:http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com- Hide quoted text -

- Show quoted text -

Or use Optoisolators.
1N34's (Or the LTV847 Quad)

Actually, depending on how much wire TF will have connected, Opto's
might not be a bad idea anyway. -mpm

 

[mpm]

Florida summers are pretty bad too, for different reasons.

Yeah.... you're probably thinking lightning damage.
Try 3-weeks without electricity everytime a hurricane passes over.

Hurricane season starts next week.
(That Colorado winter is starting to look downright inviting.)

-mpm

 

[Rich Grise]

He was a drunk.

Yeah, but he wrote some really cool stories.

The point being, if you're still using wire-wrap, you must be in some
kind of time warp.

Maybe I should have checked for the spirit of Rod Serling. ;-)

Cheers!
Rich

 

[Spehro Pefhany]

I had to take my Malibu back to Piper in Boca Raton several times for
maintenance. The thunderstorms and humidity were quite impressive!

I used to smoke then. I would go out on a back balcony to enjoy the view of
a small pond lined with trees.

One night I noticed a pair of eyes staring back at me. They belonged to the
biggest alligator I have ever seen. I know how fast they can run, and I
don't mind saying that frightened the daylights out of me.

Then I discovered the door had closed and locked, and there was no way to
get back in.

Fortunately, a waitress decided at that moment to take a smoke break, and
came out on the balcony. I showed her the alligator, but she didn't mind.
She knew all about him. But that was the end of smoke breaks for me

Is that what you were referring to?

The thunderstorms (and resulting electrical disturbances), yes. Never
had a circuit affected by a 'gator, AFAIK.

A story you might enjoy:-

http://tinyurl.com/288q4z

Regards,

Mike Monett

Best regards,
Spehro Pefhany

 

[Mike Monett]

[...]

The thunderstorms (and resulting electrical disturbances), yes. Never
had a circuit affected by a 'gator, AFAIK.

A story you might enjoy:-

http://tinyurl.com/288q4z

LOL! How on earth do you find those things? Thanks.

I agree. Don't mess with alligators. They are truly evil.

Especially when they give you a "cold reptilian stare".

I know what that means. It means "dinnertime" in alligatorese

Best regards,
Spehro Pefhany

Regards,

Mike Monett

 

[MooseFET]

Yeah, but he wrote some really cool stories.

The point being, if you're still using wire-wrap, you must be in some
kind of time warp.

Yes I got the point. I was refering to an incident in the past.

Maybe I should have checked for the spirit of Rod Serling. ;-)

<VOICE PITCH=HIGH>
didit-didu-didit-didi
</VOICE>

 

[Donald]

I still have my WSU-30M - I used to wire-wrap stuff all the time.

Have you seen that price for one of these lately ???

I still have a few around, but the wire stripper broke off.

I thought I would be a new one, but $25+ was just too much.

donald

 

[joseph2k]

s/practicioners/practitioners/
s/practitioners/phools/

I've found that anything below -20 dB is inaudible anyway, except for the
subliminal effects, if any.

Cheers!
Rich

Rich, "-20 dB" with no units indicator is a ratio between two signals, not
an absolute value. -20 dB referred to a shuttle takeoff at 1000 meters is
still very, very loud. -20 dBm is still a solid signal, about what you get
from a telephone with a soft voiced person. What scale did you really
mean?

 

[krw]

Rich, "-20 dB" with no units indicator is a ratio between two signals, not
an absolute value. -20 dB referred to a shuttle takeoff at 1000 meters is
still very, very loud. -20 dBm is still a solid signal, about what you get
from a telephone with a soft voiced person. What scale did you really
mean?

I read it as a -20dB signal is inaudible buried in the 0dB signal
(I.e. "noise *ratio*").