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Jinx | 1 Jan 01:59
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Re: [EE] Current Production Digital Clock Chips

> The first thing you need is one line that goes high and low once
> a second

That is so easy. With hindsight !!

There are common ways to do it

(1) use a single crystal for clock and core
(2) separate crystals
(3) count mains cycles

An example of (1) would be to have, for example, a 19.6608MHz
on the OSC pins and use one of the PICs timers (or, more accurately,
hardware counters) to divide this frequency down

So, the PIC's Fosc will be 19,660,800/4 = 4,915,200Hz

If you use the 16-bit TMR1 as the divider, it's first loaded with 0x4000,
which equates to d49152 counts below the rollover of 0x0000. Therefore,
it takes 49152 transitions of Fosc for TMR1 to count up to 0x0000, and
TMR1IF to be set (which can be polled or used as an interrupt). As Fosc
is 4,915,200Hz, then this will happen 100 times/sec. That can be further
divided down with a RAM register to get 1Hz

Note that power consumption rises per MHz

TMR1 can also have its own crystal, independent of the core. Generally
this would be a 32768Hz "watch" crystal. Again, you pre-load TMR1
with a value to get the division you want. If you used TMR1 in 16-bit
free-run mode, it takes 65536 counts for a cycle, or 0.5Hz ( = 32768/
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Jinx | 1 Jan 02:11
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Re: [EE] Current Production Digital Clock Chips

> One other thing I might pursue is to look at the SPI or I2C RTC
> (Real time clock) chips available

That's a good suggestion. Philips have a few very cheap RTC ICs
with an I2C interface (PCF8573 comes to mind). ISTR some have
an independent 1Hz output too as well as various alarms

I've used them a couple of times but have to say I wasn't too happy
about the drift. Maxim offered a TXCO (temperature compensated)
version in one of their newsletters but the price was .... pricey

A lot of old PCs used the MC6818 IC and they can be found on old
motherboards. I think they were the basis of the Dallas modules, which
had an internal battery. They'd all be long-dead now

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windell747 | 1 Jan 01:51
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[PIC] Using PIC to modify RC speed controller signal.


So here is the application
I'm planning on using a pic to take the speed controller signal from the
reciever in an RC car and modify it using the pic so that the output of the
PIC will go to the speed controller. The purpose for modification is to
scale the input speed commands to either 25%, 50%, 75%, or 100%(unmodified)
of the original speed command coming into the pic. I have an understanding
of the theory of operation of the RC speed control/servo signals in that the
signal consists of a pulses ranging from 1ms to 2ms repeating at 60Hz. 1.0ms
to 1.5 is reverse, 1.5 to 2.0ms is forward and 1.5ms is neutral. 

Here is what I'm thinking about doing.
What I am planning to do is use an interupt to detect the rising edge of the
incoming signal that will start incrementing a timer. Then another interrupt
will be detected on the falling edge of the signal. The counter value will
then be scaled and reloaded into a register where the pic will generate the
scaled pulse at the output by pulling an output pin high and begin
decrementing the counter and then generate an interrupt when the counter
overflows and then pull the pin low.

Background and Problem
I'm a mechanical engineering student and I'm familiar with combinational
logic and sequencial logic, however I am new to the PIC and programming with
interupts. I've been doing some reading online and in some hobbyist
magazines, but what I would like to do is purchase a book on pics that will
tell me from the ground up how to develope a circuit using a pic. This would
include code examples as well as circuit board suggestions. I understand
that there are many pics to choose from some with some that dont have
interupts enabled while others do.
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Joseph Bento | 1 Jan 01:57

Re: [EE] Current Production Digital Clock Chips


On Dec 31, 2008, at 4:57 PM, Forrest Christian wrote:
>

> You might want to pick up an EasyPIC5 board from mikro-e, or their us
> distributor circuit-ed.   Plus, start with the free Mikro-Basic or
> Mikro-C compiler, both can be upgraded to the full version if needed
> later.  I might be inclined to point you toward BASIC, although if you
> can get your head around C, that would work as well or better.

I have been looking at Mikroelektronika's products for some time.  I  
have their free C compiler, and have wondered about the development  
boards.  (Interestingly, you can order the EasyPic5 directly from the  
Mikroe website for about $20 cheaper than from Circuit-Ed.)  The  
EasyPic5 looks like a good value.  However, since I have a pretty  
extensive junkbox, I wonder if a product like this would enhance my  
learning.  I already have the majority of any needed components that I  
can assemble on a solderless breadboard for experimenting and  
learning.  I'll admit to liking 'toys' though, and having everything  
on one board might be convenient.   Of course, like everyone else, I'm  
a bit more conservative in spending money nowadays.
>
> Most "line powered" clocks are actually timed from the 60 hz line.

I've always liked this option.  I have found line-based clocks to be  
as accurate if not more so than most crystal controlled clocks.  My  
understanding is the 60Hz line in the US / Canada is spot on, and I  
imagine the 50Hz throughout Europe is likely just as stable.  Some  
other countries, however, apparently do not have as reliable a power  
source, and xtal control is a better option.
(Continue reading)

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Jinx | 1 Jan 03:10
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Re: [EE] Current Production Digital Clock Chips

> understanding is the 60Hz line in the US / Canada is spot on, and
> I imagine the 50Hz throughout Europe is likely just as stable

In most developed countries the national grid is well-regulated and
providers would have to have comply. Note that this doesn't
necessarily mean they have to stick to exactly 50Hz or 60Hz, but
that they are required to generate a certain number of cycles per
day

For example, during peak periods (eg 8-9am, 5-6pm) the frequency
would possibly drop to 49.something and in off-peak (overnight) the
frequency will rise to 50.something

Therefore it is possible for a mains-derived clock to be inaccurate
for much of the day but overall, comparing day-to-day measurements,
has good repeatability

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Forrest W Christian | 1 Jan 03:29

Re: [EE] Current Production Digital Clock Chips

Joseph Bento wrote:
> I have been looking at Mikroelektronika's products for some time. I 
> have their free C compiler, and have wondered about the development 
> boards. (Interestingly, you can order the EasyPic5 directly from the 
> Mikroe website for about $20 cheaper than from Circuit-Ed.) The 
> EasyPic5 looks like a good value. However, since I have a pretty 
> extensive junkbox, I wonder if a product like this would enhance my 
> learning. I already have the majority of any needed components that I 
> can assemble on a solderless breadboard for experimenting and 
> learning. I'll admit to liking 'toys' though, and having everything on 
> one board might be convenient. Of course, like everyone else, I'm a 
> bit more conservative in spending money nowadays.
It all comes down to how much time you want to spend on wiring the stuff 
up initially versus the solderless breadboard thing.  

The thing I like about the easypic boards are that you can start coding 
without doing much, if any, wiring.   Plus, with a few of the addon 
boards, you can actually try quite a bit without resorting to a 
soldering iron or a solderless breadboard.   When I am playing with 
something that I can't just use the on-board resources, I then use the 
easyconnect boards and some wires to a solderless breadboard.

It allows me to cut the amount of time messing around with the whole 
"base" circuit on the solderless breadboard to zero.   I instantly have 
a PIC wired up to a set of LEDS to see I/O port status, and other 
peripherals, without having to do this all on the breadboard.   Not to 
mention USB powered and onboard programmer, so I don't have to screw 
with the power supply for each board.  For me, I have found that it is 
worth it to have the easypic4 within easy reach for when I am initially 
starting the design to prove that what I am trying to do will work.
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solarwind | 1 Jan 05:18
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Re: [EE] Popping Bubbles

On Wed, Dec 31, 2008 at 10:41 AM, Ariel Rocholl <foros <at> arocholl.com> wrote:
> I would point out that I have been using rechargable NiMh batteries very
> successfully to feed uC low current demanding circuits, and using them more
> and more. It is not only a fact that floating ground problems dissapear with
> this approach, but you get the additional benefit of very limited damage to
> other electronics if your circuit is doing something fun.
> For a LCD circuit like the one you are using, I would definitely recommend
> using batteries for testing.

Advice taken. I'll be making a multiple voltage battery system -
attaching voltage outputs at useful intervals as well as common
voltage regulators, current limiting resistors and so on.

What battery type do you recommend, and what mA . h rating?

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Jonathan Hallameyer | 1 Jan 07:00
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Re: [EE] Switchmode LED driver advice

I've changed what Ive wanted to do a bit, I decided that a TL5001
driving a plain buck converter rather then the buckboost of the maxim
chip, and I'll use a TI current shunt amp with a gain of 20 to keep
the feedback voltage from being an issue. It would be more similar to
the schematic Jinx attached, It goes to a higher frequency then the
maxim chip so I can use a compact inductor. Plus spare TL5001's and
parts to go with it might be a tad more versatile then the maxim chip.

Some of the appnotes on TI's website have helped me spec parts for it
without as much SWAG.

Hopefully I can draw up a schematic and make a decent single sided
board for easy etching soon :)

-Jon

On Wed, Dec 31, 2008 at 6:57 PM, Jinx <joecolquitt <at> clear.net.nz> wrote:
> Jonathan, if you want to try something more along the lines of
> what Russell was talking about, have a look at this controller
>
> http://home.clear.net.nz/pages/joecolquitt/5w_luxeon_sm.gif
>
> http://home.clear.net.nz/pages/joecolquitt/5w_luxeon_table.gif
>
> It's for a 5W Luxeon. AIUI the one you want to use is 12W
> (that's bright - ya havin' a party ?). Russell may be able to suggest
> coil and semi mods for that extra output current
>
> You could also search out the candlepower forum
>
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Tony Vandiver | 1 Jan 07:08

Re: [PIC] TEST AGAIN

Hi Jim,

    My guess is that either the subject or from address is getting 
blacklisted by an upstream spam filter by your ISP.  If you have spam 
assassin provided by your service provider, you can try adding the 
piclist email address to your white list (assuming you have access to 
the jpes.com email server).  If you get this email (sent to you and cc'd 
to the list), it's probably the To: address that's getting spammed.  ISP 
spam filters have been getting a lot more agressive lately, and if the 
somewhat automatic algorithm decided to blacklist the mit.edu address, 
it would be like flipping a switch.

Good luck,

Tony

jim wrote:
> All,
>
> I changed a couple of settings in my email tool (Outlook Express) to hopefully turn off the spam filters.
> Let's see if this has any effect.    This is a strange problem.  I received the last email from the list yesterday
> at about 1:00 PM (CST).  Then it all just quit.  No steady slowdown of emails from the list.  Just the normal
> rate of a few per hour.  Then nothing.  Like someone turned off a switch.
>
> I'm out of ideas.  And I don't know how to get things going again.
>
> I have noticed, as other have so kindly pointed out, that I can get emails addressed directly to me, but if
they 
> go through the PICLIST, they don't show up in my inbox.
>
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Richard Prosser | 1 Jan 09:12
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Re: [PIC]: TEST AGAIN

2009/1/1 jim <jim <at> jpes.com>:
> All,
>
> I changed a couple of settings in my email tool (Outlook Express) to hopefully turn off the spam filters.
> Let's see if this has any effect.    This is a strange problem.  I received the last email from the list yesterday
> at about 1:00 PM (CST).  Then it all just quit.  No steady slowdown of emails from the list.  Just the normal
> rate of a few per hour.  Then nothing.  Like someone turned off a switch.
>
> I'm out of ideas.  And I don't know how to get things going again.
>
> I have noticed, as other have so kindly pointed out, that I can get emails addressed directly to me, but if they
> go through the PICLIST, they don't show up in my inbox.
>
> If anyone has any further ideas, I'm open to suggestion.   Just make sure you send any replies to me at my
> email address directly, (jim <at> jpes.com).
>
> I appreciate the help.
>
>
> Thanks all,    Jim

Jim
Does your ISP/mail server do any filtering? They may have changed to a
more aggressive filter .

If it does do filtering, you may be able to turn it off or change the setting.

RP
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Gmane