gmane.comp.hardware.microcontrollers.pic

[EE] Ground return of the caps of a Xtal

Electron — 2012-05-26T13:48:18

Hi!
Should I return the ground of the caps of a xtal to the nearest Vss pin
of the MPU, or returning them to the opposite side, where I have a ground
plane readily available, is exactly the same?

I heard the first would be better.. but will it really make any difference?

Cheers,
Mario

[OT]Interesting research for NZ quake susceptability

cdb — 2012-05-26T00:57:47

 Victoria University (Wellington, North Island) has been doing research 
into the south island quakes along the Alpine Fault. They've dicovered that 
NZ is constantly shifting with ongoing long lasting (30 minutes) quakes at 
a depth of 45 klm below the surface.

article here 
:http://www.abc.net.au/science/articles/2012/05/24/3510050.htm?topic=enviro
&WT.svl=healthscience5
--
cdb,  on 26/05/2012

[EE] possible ways of dealing with noise on a serial bus ?

Jason White — 2012-05-25T19:05:16

This question is completely theoretical. I'm just curious as it
pertains to something
I may be building in the near future.

Lets say I have 25 devices spread throughout a building connected through a
low speed (50Khz) synchronous serial bus at 5 volts. Lets say we have 50 feet
(or so) of cable sloppily daisy chained in between each of the devices
(around high
amounts of florescent lighting). Would noise be a likely issue with
the bus ? If so
what would be an effective way of dealing with it. (differential
signaling, perhaps ?)

Thanks
Jason White

[OT] Spacex delivers a Dragon to ISS

Walter Banks — 2012-05-25T15:00:30

I have been a big fan of SPACEX for a long time. As a company they have
practiced a lot of solid engineering and science in developing their
various space technologies. They have shown tremendous attention to
details in the work they have done.

Spacex has demonstrated that they learn from their mistakes and they
have not let any pressures force them to do anything that they feel not
fully prepared for.

This mornings capture of the Dragon capsule by ISS has demonstrates how
this approach has paid off.

As one of many companies moving into the space transportation business
we are seeing a new era in space exploration that will not be dominated
by just finding a solution but in selecting which innovation solution
should be pursued.

The possibilities start to get interesting with Rutan/Virgin preparing
to carry passengers into space for a short time and private companies
soon to routinely launch and support space missions.


Walter..

[PIC]:Difference between BOR and LPBOR

Ruben Jönsson — 2012-05-25T09:15:12

Hi,

I have been studying the datasheets for some of the PIC10/12LF parts. These 
have both the standard Brown Out Reset (BOR) and also a Low Power BOR (LPBOR). 
I can't seem to find any difference between these (not even difference in 
current consumption).

The datasheets are marked as preliminary and no graphs or charts are available. 
Having both a standard BOR and also an LPBOR seems to indicate that there are 
some drawbacks using the LPBOR over the BOR. Why would there otherwise be both 
in the same chip?

I have an idea of using one of these chips for power management for cheap solar 
PV cells with low capacity NiMh batteries. These work fine when the batteries 
are somewhat charged but when the batteries are almost completely discharged, 
the circuit hangs in a mode where more current is drained than can be supplied 
by the PV cell so the batteries never gets charged and the circuit won't come 
alive again, no matter how much sunshine there is.

I did a circuit that senses the voltage drop on the batteries in this case that 
cuts the power to the rest of the circuit for about 90 seconds, giving the PV 
cells a chance to charge the batteries. When the batteries are charged enough 
there is a much smaller voltage drop and the rest of the circuit is alowed to 
draw current. As soon as the battery voltage/capacity is good and the rest of 
the circuit can start, it runs intermittently alowing the batteries to be 
continually charged.

The current circuit is made around an OP amp and two diodes as a voltage 
reference. This could be made much smaller with just one SOT23 PIC10LF320, 
using the brown out reset circuit to detect the voltage dip (1.8 - 2.10V). I 
can then also get an external shutdown input, which also simplifies the rest of 
the circuit.

/Ruben

===========================================
Ruben Jönsson
AB Liros Electronic
Box 9124
200 39 Malmö Sweden
www.liros.se
Tel +46 40142078
============================================

[EE] TV Tuner Based Spectrum Analyzer

Herbert Graf — 2012-05-24T19:15:29

Hello all,

well, after a long delay, I've been able to dedicate a little time to my
idle project: a home built spectrum analyzer based on a TV tuner front
end.

I've found what I believe the perfect tuner for me (mostly because it's
something I have in my hands):

http://www.datasheetarchive.com/indexdl/Datasheet-028/DSA00488547.pdf

It's a Temic 4036 RF front end module. I found it on a WinTV PC TV tuner
PCI card. 

It's a I2C based tuner, with single 5V power supply (has an onboard
DC-DC to get the 33V needed by the tuner). I stuck the card in a PC,
booted Ubuntu, attached a protocol analyzer (thank you beta version of
the BitScope software, was a major time saver!) on the I2C pins, started
TVTime and changed channels. The module is being programmed exactly as
the datasheet says it should be!

So, with that out of the way, what would be my next step?

First off, the module outputs CVBS (at baseband), and something labelled
IF2 (at 45.75 MHZ). Obviously I need an RSSI circuit. But do I first
have to "tune" the output somehow? 

What I'm envisioning (and note, I no NOTHING about RF stuff, so this is
very much a learning project for me) is using a second tuner (some sort
of home built one chip thing with RSSI output perhaps?) that "tunes"
somewhere in the CVBS output with a bandwidth of say 10kHz? So basically
sweeping would be two steps, set the TV tuner to a channel, then sweep
the second tuner across the ~4MHz bandwidth of the CVBS or IF output.
Then step the TV tuner to the next range, and sweep the CVBS or IF
output. Combined I could get everything I need.

Does this sound at all reasonable or am I WAY out of wack here?

Should use the CVBS or the IF output?

Anybody have chip recommendations for how I might build the second
tuner, one hopefully with an RSSI output?

Is there a simpler way to what I'm after? What kind of resolution should
I aim for?

Thanks for any pointers!

TTYL

[OT] Interesting newish embedded programming language

cdb — 2012-05-24T06:01:09

 In EEJournal they have an article on B# a cut down  but microcontroller 
orientated C# language, According to the B# webpage it can work in uC that 
have less than 24KB of Flash and less than 2KB of RAM, 8 - 32 bit 
controllers.

Not much else to say as unfortunately to get the specs and to access the 
compiler requires emailing B# themselves.

http://www.eejournal.com/archives/articles/20120523-objectlesson/

http://www.bsharplanguage.org/index.html

Now who is going to invent a computer language using the extra letters of 
the alphabet of the latin and germanic languages.

I'm going for Icelandic and ώψπε.

Colin

--
cdb,  on 24/05/2012

[EE] Raspberry Pi challengers

2012-05-23T15:07:39

Looks like the Raspberry Pi market is garnering more challengers ...


http://www.bbc.co.uk/news/technology-18163419

[EE] Serial over Ethernet options

Denny Esterline — 2012-05-23T14:11:25

As the title implies, I'm looking for some serial over Ethernet solutions.

Skipping some of the messier details, I have a few hundred devices in the
field that need to have some config options changed. Normally this is done
via rs232 connection to a PC -it's a little more complicated now that
they're in customer hands in 28 different states. So, I can put a tech to
work for the next year and really rack up his frequent flyer miles or I can
find a connectivity solution and do it remotely.

What I'd like to be able to do is send the customer a "black box", have
them plug it into their network and my device and give me a call. Using a
similar unit at my location, we have serial access to a PC in my office. I
realize that having that happen seamlessly and without the customer
configing it to their network and being able to connect to it from my end
without even knowing what subnet it's going to end up on is a tall order...
How close can we come? :-)


-Denny

[OT] Anyone from San Diego, CA?

Tamas Rudnai — 2012-05-23T05:22:37

Hi List,

Is anyone from San Diego by any chance? I am just settling down here, and
was wondering if there are any good tool and component shops over here or
nearby?

Also any kind of information would be much appreciated which is not
necessarily related to electronics (things to see, places to avoid, good
restaurants etc)

Many thanks,
Tamas

[PIC]:PIC12F675 Servo motor wobble problem

yamanoor sairam — 2012-05-23T03:11:05

Hello All,

I had written to the list long time back regarding the drive of servo motor using a potentiometer and a PIC12F675. I was successful in doing driving the same. I got back to working on this project and I am happen to face a new problem.  

When there is no load on the motor, it works perfect. When I load the motor, it keeps wobbling. I think the motor is not able to drive the load or there is a small slippage that is causing the problem. All I wanted to do was that the motor should rotate between 90 and 180 degrees when a switch is toggled.

Should I just switch off the motor when it is near the desired position? It looks like the motor has reached 3 degrees and trying to correct the angle and slipping off to -3 degrees. It keeps repeating this cycle.

 I am posting a snippet of the code:

 if(GPIO & (1<<3))
                   {
                   if(servoVal>=(1499))
                   {
                    servoVal = servoVal-(quotient*10);
                    }
                   // do_servo();
                    }
                 else         if(!(GPIO & (1<<3)))
                                {
                                if(servoVal<=(2300))
                                {
                                servoVal = servoVal+(quotient*10);
                                 }
                                  //do_servo();
                                }

Sai

[EE] Electric bicycle controller

Joe Wronski — 2012-05-22T14:58:49

Hello collective brain,

A while back, I asked about removing potting from a circuit, and my 
attempt didn't work.  The circuit was a motor controller for an electric 
bike.  I ended up salvaging some a heat sink, connectors and cables from 
the controller, but otherwise it is now a shapeless lump of plastic and 
components.

The bike was a thinkbike, manufactured by Ford motor company in the 
early 90s.  It had a "thinbrain" on the handlebars with an 18 pin 
PIC16C5x (54?) on it.  I've replaced the old PIC with a 16F88, and have 
code that reads the Hall sensor throttle control and outputs a PWM 
signal from 0 to 100% of full current.  The plan is to send this PWM 
signal to a 24V, 400 watt, 555 based PWM controller that I bought.  I 
would cut out the existing 555 controller on that board.

In case sending a 12 kHz PWM signal down 3 feet of 8 lead cable doesn't 
work well, I would need to add another controller at the bottom end, and 
wonder what would be a good candidate for a small simple board that I 
can buy off the shelf for this.

* Communications protocol between the 2 boards is not critical.  The 
current thinkbrain at the handlebar has 2 lines D0 and D1 that could be 
used and they have resistor termination, one with a series 100 ohm.

* I would need 2 analog channels, as there are additional Hall sensors, 
one for pedal torque and one for wheel speed.

The pedal torque mechanism was interesting.  I thought it was just a 
pedal rotation sensor, but rotating the pedals produced no output. 
Jamming the output gear and putting pressure on the pedal produces 
output.  It has a planetary gear mechanism with a spring loaded outer 
gear which, when torque is applied, floats enough to move two magnets 
sandwiching a Hall cell.  I think someone on this list has worked with a 
pedal torque sensor and I wonder how I might use this signal to vary 
motor output.
The battery pack is another issue.  It is a 24V pack made of 2 12V, 12AH 
sealed lead acid batteries.   There is a bq2013H gas gauge IC and a 
PIC16C711 and a handful of resistors, caps, and transistors on the 
circuit board.

I only want to get it running as a learning and demonstration exercise, 
weatherization and reliability not really critical.

So, I'm looking for ideas on:
o Wisdom of sending PWM down 3 feet of cable, and alternatives.
o Usage of wheel speed and pedal torque signals on an electric bike.
o Experiences using the TI bq20xx gas gauge IC and talking to it with a uC.

Thanks group.

Joe Wronski

[EE] How would you ensure fast power ramp up rise time?

Electron — 2012-05-22T06:43:54

Hi,
I have a IC which, in the datasheet, is said to need a powerup rise time not
slower than 100uS in order to initialize correctly. Effectively it doesn't work
if the power ramps up slow, and there's no reset input, power must be disconnected
in order to attempt a new successfull turn on.

How would you ensure fast powerup rise time? The power turns on / ramps up very
slowly, and I can't help it.

I am currently investigating two options:

1) a PNP/NPN or PMOS/NPN pass circuit at the output, and using a voltage regulator
with error output (LP2951): when the error is signaled, no power is passed to the IC.
I would prefer to power the problematic IC directly via the error output, but it sinks
too much current (even 50 mA), so the PNP/NPN power switch is necessary, but it will
introduce a voltage drop, which is gonna cause errors (it's an analogue IC).

2) using a voltage supervisor (e.g. NCP302HSN40T1G) BEFORE the voltage regulator, to
control the shutdown pin of the latter (a LP2951). Seems like a good idea, however
the NCP302HSN40T1G has a 10V voltage input limit which ruins the 30V needed and
offered by the LP2951.

How would you handle this problem?

And, regarding 1) can you suggest me a cheap and small logic level PMOS transistor?
It needs to pass (or not) +3.3V with minimal voltage drop even at 100mA peak current.
For "logic level" I mean that with the source at +3.3V and the gate at ground, it
should ~fully conduct.

Thanks a lot for any help.

Mario

[EE] Anyone know anything about galvanometers?

William Couture — 2012-05-21T20:19:02

Someone I know picked this up, but can't tell if it is complete, or
how to put the
pieces together.

Clues?

http://imgur.com/a/U7V0d

Thanks,
   Bill

[PIC] PIC32MX575F512H SPI 8 Bit Slave Mode

2012-05-21T15:35:59

Has anyone out there worked with the PIC32MX575F512H part? Specifically
using its SPI module in slave mode. I have it setup to act as a slave, 8
bit mode, with SS enabled. When bursting 250 bytes from a master to the
575 part, all bytes are received okay, but the part is skipping bytes
sending back to the master. The transmit empty buffer interrupt is only
generating an interrupt every 16 spi clock cycles (it acts as if the
transmit portion is stuck in 16 bit transfer mode). I'm NOT using the
enhanced buffer mode.

I have the code working fine on the smaller PIC32MX150F128D part and
have reviewed the errata sheet for the 575 part for any anomalies with
the SPI module (none that apply to my situation). I have also reported
this problem to Microchip (no word back yet).

So, does anyone know if there is or might be a problem in the firmware
of the 575 part?

Thanks,
Ross

[EE] How would you ensure fast powerup rise time?

Electron — 2012-05-21T14:21:32

Hi,
I have a IC which, in the datasheet, is said to need a powerup rise time not
slower than 100uS in order to initialize correctly. Effectively it doesn't work
if the power ramps up slow, and there's no reset input, power must be disconnected
in order to attempt a new successfull turn on.

How would you ensure fast powerup rise time? The power turns on / ramps up very
slowly, and I can't help it.

I am currently investigating two options:

1) a PNP/NPN or PMOS/NPN pass circuit at the output, and using a voltage regulator
with error output (LP2951): when the error is signaled, no power is passed to the IC.
I would prefer to power the problematic IC directly via the error output, but it sinks
too much current (even 50 mA), so the PNP/NPN power switch is necessary, but it will
introduce a voltage drop, which is gonna cause errors (it's an analogue IC).

2) using a voltage supervisor (e.g. NCP302HSN40T1G) BEFORE the voltage regulator, to
control the shutdown pin of the latter (a LP2951). Seems like a good idea, however
the NCP302HSN40T1G has a 10V voltage input limit which ruins the 30V needed and
offered by the LP2951.

How would you handle this problem?

And, regarding 1) can you suggest me a cheap and small logic level PMOS transistor?
It needs to pass (or not) +3.3V with minimal voltage drop even at 100mA peak current.
For "logic level" I mean that with the source at +3.3V and the gate at ground, it
should ~fully conduct.

Thanks a lot for any help.

Mario

[OT]:A123

John Ferrell — 2012-05-20T12:40:23

This time with tag!

Bummer! I hate it when the most promising candidate is threatened.

http://seekingalpha.com/article/596441-storm-warnings-at-a123-systems?source=yahoo

[OT]:: Earthquake Northern Italy 20 May 02100 UTC.

RussellMc — 2012-05-20T11:07:35

Earthquake, Northern Italy,
2pm Sunday afternoon NZ time.
2am Sunday UTC.

Smallish but shallow and nasty - M6 at only 5.1 km deep.
Probably 10's to 100' dead :-(.

Immediately under Solara if the ccordinates are correct.
(Solara does not feature on their list at all but is just about exactly the
distance and direction from Camposanto that they say :-(.)
Effects are often worse at a radius about equal to the depth).

Wikimapia: http://www.wikimapia.org/#lat=44.776&lon=11.09&z=13&l=0&
m=b&search=44.776N%2C%2011.0<http://www.wikimapia.org/#lat=44.776&lon=11.09&z=13&l=0&m=b&search=44.776N%2C%2011.09E>

USGS PAGER page: http://earthquake.usgs.gov/earthquakes/pager/events/us/
b0009tk0/index.html


        Russell

[[BCC: RVKR passed nearby in 2003.]]

[OT] PC on a stick for 74 USD

Joe Wronski — 2012-05-20T00:13:21

Not sure what to make of this.  How does it compare with Raspberry, 
other than the price and the Android OS?

http://www.engadget.com/2012/05/18/mk802-beats-cotton-candy-to-market/

Currently sold out at Aliexpress.com, but more coming June or so.

I don't even know what Cotton Candy refers to, but I guess ICS is Ice 
Cream Sandwich.

Joe W

[OT] Mechanical Principles

IVP — 2012-05-19T02:19:35

Searching for ideas for a linkage a few weeks ago I came across this

Mechanical Principles by Ralph Steiner, 1930

http://www.youtube.com/watch?v=Y5pen3QMgzQ

Fascinating. And I got more than one answer to my problem

Joe

[EE] Looking for decent but small camera

Dwayne Reid — 2012-05-18T21:04:19

Good day to all.

I just spent the morning on-site at a customer's location and was 
thinking that it really was too bad that I wasn't documenting my work 
with pictures.  We do that all the time in my shop and I used to do 
so on-site with my Sony Mavica CD-1000 camera.  That camera took 
GREAT pictures but its just too darned big to pack around anymore.

So: I'm looking for a small camera that has a decent macro mode and 
reasonable zoom range - 5:1 would be great.  Great battery life from 
rechargeable "AA" cells would be a bonus.

This doesn't have to be the cheapest camera available - I don't mind 
spending extra money for extra performance.

Do note that I'm NOT looking for a professional or semi-pro camera 
like Canon's high-end stuff.

I should also mention that I live in Canada and would prefer to 
purchase from somewhere in North America.

Any suggestions gratefully accepted.

Many thanks!

dwayne