Nabble - MicroControllers - PIC

Re: Shopping at MASTERS 2008 -- pricelist

2008-07-24T21:17:22Z

Most likely too late to be useful, but here it is anyway:

http://maksimov.org/masters_pricelist.pdf
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From forum: PIC - [PIC]

question on a fall edge trigger

2008-07-24T20:40:22Z

Hi:

I'm designing a battery charger with a power factor correction pre-converter. This critical conduction mode PFC chip (L6562 from ST), has a so-called compensation network, so that when load changes abruptly, it will slowly modify the output power to realize a high power factor.

But since mine is a charger, there is almost a constant load, thus this function is not really useful. My worry is: when the load is suddenly removed, the chip might be unable to respond fast enough.

I wonder is there such a transistor circuit, which does nothing at no load or full load, but only outputs high when load is removed (fall edge)? This may involve some power, so I think simple flip-flops might not be useful.

Thank you for any opinions.
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From forum: PIC - [EE]

Re: FET question

2008-07-24T20:29:23Z

Listas de Correo wrote:
> I have tried connecting and disconnecting the ground wire of the rabbit,
> directly, to GND and it successfully starts every time.

I'm ready to suggest that when using the FET the voltage rises too
slowly for the Rabbit to start.

Can you test again using the FET but driving the gate manually, first
with a jumper wire, and if that works, then with a resistor? Because if
it starts with the jumper driving the FET but not the resistor, that is
a risetime problem.

Cheerful regards,

Bob
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From forum: PIC - [EE]

Re: FET question

2008-07-24T20:26:20Z

> Your sure the fet is into its saturated region at 3.3V
> gate drive?
> that's quite low, not impossible just uncommon is all.

Looks OK enough from the spec sheet curves.

Looking at V across module with a scope at turn on may give
some clues.

An easy enough test is to try a high side driver.

Disconnect FET drain from model gnd.
Ground module gnd.
Small pnp transistor with at least 500 mA rating (BC327 or
similar)
Beta of 100 at least at 500 mA.

Emitter to V+
Collector to module V+
Base via say 470 ohms to FET drain.

You now have a high side switch with good drive

If that works it gives you a clue.
If not then the clue is different but not so clear.

I assume that you have the MOSFET gds connected OK :-).

Russell

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From forum: PIC - [EE]

Re: FET question

2008-07-24T20:15:54Z

> The 450 mA at 0.15 ohm

This d/s says 0.2R @ 4.5V, 0.3R @ 2.5V

http://www.fairchildsemi.com/ds/FD/FDV305N.pdf

Take a look at Figures 2 and 4, you might find that Ron is higher than
you planned for

If I'm asssuming correctly, quick look, and the normalised Ron is *1.1
@ 3.5V and 0.5A, then that would mean actual Ron in circuit is 0.33R,
so you'd be losing 0.450A * 0.33R = 0.15V. If so, that puts the voltage
available for the Rabbit at 3.15V

Can you bump up the regulator output a little ?

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From forum: PIC - [EE]

Re: Why most published research findings are false.

2008-07-24T20:09:13Z

>>> Get 20 guinea pigs. Put them in an enclosure. Surround
>>> the
>>> enclosure
>>> with 5,437 mobile phones. Wait a year and see what
>>> happens.

>> People have done experiments that are close to that.
>> As one might expect, the results vary between experiments
>> and the conclusions are debated.

> Well if the guinea pigs grow an extra head, or if they
> start walking
> into walls, then I think it's fair to speculate that it's
> caused by the
> mobile phones. (Assuming of course, in the absence of
> mobile phones,
> they don't grow extra heads or walk into walls).

Yes.o problem if that was the level of response.
However, what does happen is that people get results which
show with statistical significance that there is/isn't
(choose one) something happening. People can/can't replicate
their results (or can't/can) and people publish papers
drawing all available conclusions (not necessarily in the
same paper).

At the very large scale there are correlations present
between increased disease risks for workers in some
industries that suggest that EM fields may have causal roles
in such things. Some cell-phone/cancer studies show a clear
linkage and others show none.

All adds grist for the subject line of this email.

Russell

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Re: FET question

2008-07-24T19:56:35Z

Apptech wrote:

>> I have a circuit with a MOSFET driving a RCM4400W (A
>> Rabbit module
>> with wifi, that need 80mA on startup and 450mA when the
>> wifi module is on),
>> and it is not working.
>>
>
> FET should tolerate a zero ohm connection from PIC.
>
> Try this.
> - Set up system as described.
> - Add switch across FET drain-source.
> - Open switch
> - Enable system via FET.
> - Close switch.
>
> IF it works under that condition the FET is suspect as an on
> switch.
> FET should have about 0.15 ohm on resistance as described.
> Should be OKish although the module spec is 3V3 +/- 5% so
> you are outside that range at 450 mA.
>
> If it fails to work then the system is probably being
> disabled in some manner by the load side open switch.
> eg having the module connected to Vdd and stray paths from
> I/O to ground may do funny things to it.
>
> Also: RF may be getting into FET. All bets off if that
> happens :-).
>
>
>
> Russell
>
>

The Fet itself might be ok with a 0 ohm drive but the PIC probably wont
be ;-> you could well be asking for a few amps of drive current (for a
very short time).
I'm wondering given the OP is using a 5.6K resistor if the miller charge
is turning the fet off again as the rabbit comes up to power (as
somebody else said its probably charging some caps and asking for a few
amps of current)

To limit the initial current you want about a 170 ohm resistor and that
should hopefully be stiff enough to handle any of that other weirdness
that goes on with fets.
Your sure the fet is into its saturated region at 3.3V gate drive?
that's quite low, not impossible just uncommon is all.

Don't know how it'll work with the rabit, but try sticking a 1 ohm
resistor in line with it, might help reduce the switch on thump.

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From forum: PIC - [EE]

Re: FET question

2008-07-24T19:55:33Z

> Unfortunally, we already have 100 boards made

Just curious - how did you come to be in this position ?

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From forum: PIC - [EE]

Re: FET question

2008-07-24T19:51:48Z

I have tried connecting and disconnecting the ground wire of the rabbit,
directly, to GND and it successfully starts every time.

The 450 mA at 0.15 ohm represent a voltage drop of 0.0225 V, that is 0.68%
of 3.3V, so the Rabbit should work with that voltage, shouldn't?

I'm trying not to consider RF yet...

On Thu, Jul 24, 2008 at 11:00 PM, Apptech <apptech@...> wrote:

> > I have a circuit with a MOSFET driving a RCM4400W (A
> > Rabbit module
> > with wifi, that need 80mA on startup and 450mA when the
> > wifi module is on),
> > and it is not working.
>
> FET should tolerate a zero ohm connection from PIC.
>
> Try this.
> - Set up system as described.
> - Add switch across FET drain-source.
> - Open switch
> - Enable system via FET.
> - Close switch.
>
> IF it works under that condition the FET is suspect as an on
> switch.
> FET should have about 0.15 ohm on resistance as described.
> Should be OKish although the module spec is 3V3 +/- 5% so
> you are outside that range at 450 mA.
>
> If it fails to work then the system is probably being
> disabled in some manner by the load side open switch.
> eg having the module connected to Vdd and stray paths from
> I/O to ground may do funny things to it.
>
> Also: RF may be getting into FET. All bets off if that
> happens :-).
>
>
>
> Russell
>
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From forum: PIC - [EE]

Re: Dual SIM mobile phone

2008-07-24T19:36:13Z

In that scenario Tomás I suggest you wait until you get here. AIS is the
only carrier (thank you Mr. Thaksin) license for dual SIM, and you have to
set it up through them on their equipment. It's still technically unlawful
to import any communications device to Thailand without a special permit and
license. That's not often enforced, but the penalties are too high and the
work arounds too easy to ignore with any wisdom. You will find that most
people simply carry 2 or more cell phones rather than draw attention to
themselves and raise unnecessary questions:-)

Regards/Roger, in Bangkok

On Fri, Jul 25, 2008 at 6:21 AM, Tomás Ó hÉilidhe <toe@...> wrote:

>
> I'm looking at getting a "dual SIM" mobile phone. I want to be able to
> put two SIM cards into the phone, and to be able to have both SIM's
> active at the same time. For instance, one minute I might receive a text
> to my Irish SIM card, while the next I might receive a phone call on my
> Thai SIM card.
>
> Anyone got any experience with these "dual SIM" phones? Are there any
> good ones out there?
>
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From forum: PIC - [OT]

Re: FET question

2008-07-24T19:10:47Z

Unfortunally, we already have 100 boards made. We can make small changes,
like putting a FET on the high side of the rabbit, but making big changes
will be difficult.

I will see tomorrow, while I'm at the office, if it is possible to change
the layout easily from low side switch to High side switch.

by the way, if I connect the rabbit directly to ground (or with a switch or
a relay) it works just fine. So, the problem is with the MOSFET...

Regards

On Thu, Jul 24, 2008 at 10:43 PM, Spehro Pefhany <speff@...> wrote:

> At 06:38 PM 7/24/2008, you wrote:
> > > 1) Besides 3.3V and the mosfet drain, what else is connected to the
> > > rabbit module? (I suspect there may be some kind of ground leakage
> > > path)
> >
> >There is no other connection in or out the rabbit. I removed everything to
> >make tests. The only connections to the Rabbit are the 3.3V line straight
> >from the MCP1826 voltage regulator and the ground line going from the
> rabbit
> >to the GND path through the FDV305N FET.
> >
> > > 2) What voltage is your PIC running at? (to determine how it is
> > > driving the FET gate) I assume that the PIC shares the same ground as
> > > the FET?
> >
> >Yes, it is the same ground. The everything is running at 3.3V
> (PIC16F67J10)
> >
> > > 3) Have you tried measuring the voltage across the rabbit module's
> > > power input (pos to neg) when the FET is turned on? (trying to
> > > determine whether there is a static on-resistance problem with the
> > > FET)
> >
> >There are 3.3V as expected. The ON time of the FET is 200 uS.
> >
> > > 4) Does the rabbit module have large capacitors on its input or a
> > > switching power supply which may have a high inrush current? (This may
> > > cause the voltage to drop sharply at startup, which may in turn
> > > trigger the module to shut itself down immediately)
> >
> >It doesn't seems to. However, it takes 450mA when the wifi module is on. I
> >know the rabbit works while the wifi is off, but it resets when the power
> >consumption increases (I should have mentioned this earlier, I know...)
> >
> > > Also, I'd suggest replacing the rabbit module with a 7 ohm resistor
> > > (approx) to simulate a 450mA load, then turn on your FET and measure
> > > how much voltage there is across the FET and across the resistor.
> >
> >I've done it with a 5.6 ohm. The weird thing is that it works just fine
> >(550+ mA). With the actual load (the rabbit) the PIC resets sometimes when
> >it is turned on, the 5.6ohm resistor has no negative effect however.
>
> That's not weird, it's expected. The module probably has a bunch of
> bypass capacitors and you're momentarily killing the supply charging them.
>
> I suggest a separate regulator with shutdown input is probably the best
> way to handle this (effectively a high-side switch with current limiting)
>
> The problem with switching the low side is that any logic pins that
> connect to the PIC or whatever could get pulled way below
> "ground" from the perspective of the the Rabbit module (eg. the PIC
> is "low", a great deal of current will flow through the protection
> diodes on the Rabbit module, possibly damaging it or causing latchup
> which would result very quickly in damage due to high currents.
>
>
>
>
> >
> > > You might also try removing the 5.6K resistor and just driving the FET
> > > gate directly from the PIC.
> >
> >Donne that. This causes the PIC to reset as soon as the GATE line is taken
> >high. I put the resistor to solve this. I also placed a 1000 uF capacitor
> in
> >the output of the MCP1826 voltage regulator, to improve this reset
> problem,
> >that I trace down to the regulator not being able to regulate on the
> sudden
> >change of load.
> >
> >What is puzzling is that with the 5.6 ohm resistor everything works as
> >expected, there are 3.3V as needed, but the rabbit won't work.
> >
> >Regards,
> >
> >Mauricio Jancic
> >Microchip Design Partner
> >Janso Desarrollos
> >
> >
> >--
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> >View/change your membership options at
> >http://mailman.mit.edu/mailman/listinfo/piclist
>
> Spehro Pefhany --"it's the network..." "The Journey is the
> reward"
> speff@... Info for manufacturers:
> http://www.trexon.com
> Embedded software/hardware/analog Info for designers:
> http://www.speff.com
>
>
>
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From forum: PIC - [EE]

Re: FET question

2008-07-24T19:00:55Z

> I have a circuit with a MOSFET driving a RCM4400W (A
> Rabbit module
> with wifi, that need 80mA on startup and 450mA when the
> wifi module is on),
> and it is not working.

FET should tolerate a zero ohm connection from PIC.

Try this.
- Set up system as described.
- Add switch across FET drain-source.
- Open switch
- Enable system via FET.
- Close switch.

IF it works under that condition the FET is suspect as an on
switch.
FET should have about 0.15 ohm on resistance as described.
Should be OKish although the module spec is 3V3 +/- 5% so
you are outside that range at 450 mA.

If it fails to work then the system is probably being
disabled in some manner by the load side open switch.
eg having the module connected to Vdd and stray paths from
I/O to ground may do funny things to it.

Also: RF may be getting into FET. All bets off if that
happens :-).

Russell

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From forum: PIC - [EE]

RE: FET question

2008-07-24T18:43:12Z

At 06:38 PM 7/24/2008, you wrote:

> > 1) Besides 3.3V and the mosfet drain, what else is connected to the
> > rabbit module? (I suspect there may be some kind of ground leakage
> > path)
>
>There is no other connection in or out the rabbit. I removed everything to
>make tests. The only connections to the Rabbit are the 3.3V line straight
>from the MCP1826 voltage regulator and the ground line going from the rabbit
>to the GND path through the FDV305N FET.
>
> > 2) What voltage is your PIC running at? (to determine how it is
> > driving the FET gate) I assume that the PIC shares the same ground as
> > the FET?
>
>Yes, it is the same ground. The everything is running at 3.3V (PIC16F67J10)
>
> > 3) Have you tried measuring the voltage across the rabbit module's
> > power input (pos to neg) when the FET is turned on? (trying to
> > determine whether there is a static on-resistance problem with the
> > FET)
>
>There are 3.3V as expected. The ON time of the FET is 200 uS.
>
> > 4) Does the rabbit module have large capacitors on its input or a
> > switching power supply which may have a high inrush current? (This may
> > cause the voltage to drop sharply at startup, which may in turn
> > trigger the module to shut itself down immediately)
>
>It doesn't seems to. However, it takes 450mA when the wifi module is on. I
>know the rabbit works while the wifi is off, but it resets when the power
>consumption increases (I should have mentioned this earlier, I know...)
>
> > Also, I'd suggest replacing the rabbit module with a 7 ohm resistor
> > (approx) to simulate a 450mA load, then turn on your FET and measure
> > how much voltage there is across the FET and across the resistor.
>
>I've done it with a 5.6 ohm. The weird thing is that it works just fine
>(550+ mA). With the actual load (the rabbit) the PIC resets sometimes when
>it is turned on, the 5.6ohm resistor has no negative effect however.

That's not weird, it's expected. The module probably has a bunch of
bypass capacitors and you're momentarily killing the supply charging them.

I suggest a separate regulator with shutdown input is probably the best
way to handle this (effectively a high-side switch with current limiting)

The problem with switching the low side is that any logic pins that
connect to the PIC or whatever could get pulled way below
"ground" from the perspective of the the Rabbit module (eg. the PIC
is "low", a great deal of current will flow through the protection
diodes on the Rabbit module, possibly damaging it or causing latchup
which would result very quickly in damage due to high currents.

>
> > You might also try removing the 5.6K resistor and just driving the FET
> > gate directly from the PIC.
>
>Donne that. This causes the PIC to reset as soon as the GATE line is taken
>high. I put the resistor to solve this. I also placed a 1000 uF capacitor in
>the output of the MCP1826 voltage regulator, to improve this reset problem,
>that I trace down to the regulator not being able to regulate on the sudden
>change of load.
>
>What is puzzling is that with the 5.6 ohm resistor everything works as
>expected, there are 3.3V as needed, but the rabbit won't work.
>
>Regards,
>
>Mauricio Jancic
>Microchip Design Partner
>Janso Desarrollos
>
>
>--
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>http://mailman.mit.edu/mailman/listinfo/piclist

Spehro Pefhany --"it's the network..." "The Journey is the reward"
speff@... Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

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From forum: PIC - [EE]

Re: FET question

2008-07-24T18:09:58Z

2008/7/25 Jinx <joecolquitt@...>:
> As an experiment, what happens if you use a relay instead of a FET ?
>

Or even a toggle switch?

RP
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From forum: PIC - [EE]

Re: Why most published research findings are false.

2008-07-24T18:04:19Z

Apptech wrote:
>> Get 20 guinea pigs. Put them in an enclosure. Surround the
>> enclosure
>> with 5,437 mobile phones. Wait a year and see what
>> happens.
>>
>
> People have done experiments that are close to that.
> As one might expect, the results vary between experiments
> and the conclusions are debated.

Well if the guinea pigs grow an extra head, or if they start walking
into walls, then I think it's fair to speculate that it's caused by the
mobile phones. (Assuming of course, in the absence of mobile phones,
they don't grow extra heads or walk into walls).

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Re: Dual SIM mobile phone

2008-07-24T17:21:36Z

:: 'm looking at getting a "dual SIM" mobile phone. I want to be able
:: to
:: put two SIM cards into the phone, and to be able to have both SIM's
:: active at the same time. For instance, one minute I might receive
:: a text
:: to my Irish SIM card, while the next I might receive a phone call
:: on my
:: Thai SIM card.

Tomas, I have a dual SIM phone, and there are some things you need to
look out for.

First: there are two types of dual SIM [hone, one has both receivers
operating at all times, the other requires you to manually choose to
receive SIM A or B. You also need to make sure that the always 'on'
type can record a missed incoming call from the SIM not being used in
a conversation at that time.

Second: There is a dual SIM phone that is produced for and provided by
a UK phone shop, these are quite good and I forget their name, but a
gluggle search for 'dual SIM UK' will bring them up eventually.

Third: For most phones you have to nominate a Master SIM and a
Secondary SIM. In practice with my phone this means that SIM A gets
full ergs on send and receive power, but SIM B, seems to struggle a
little bit.

Fourthly: Most of these phones are from one or two companies in China.
Mine is from a company called ZTC, it is not bottom of the range, but
neither is it the best. My problems are - it uses proprietary OS
(Windows like), which is not the best, menus don't always take you
where you expect, and the touch screen tool, is poorly coded as it
never takes you back to the home screen, but to a menu choice.

The batteries (it came with two) do not last very long once you've
taken or made a phone call, a 5 minute conversation can drain the
battery, though standby is about a week. It is hard to tell whether it
is the phone or the phone company, but it doesn't always register
voicemails or missed calls, can take up to a day, for the SIM B to
notify - I suspect it is the phone, as the phone company used was the
same, thoug one SIM is badged as Virgin, in reality they are Optus,
who the SIM A is provided by.

You also need to check, what GSM frequency Thailand uses, I suggest
getting at least a double band phone and if possible a triband. For
the expense, you might as well get one that can be used even in the
USA. Oh yes my one has a unique Chinese feature in its' organiser
menue, that is a fertility prediction gizmo, I tell it when I had my
last menses, what today's date is and it obligingly informs me when I
am most likely to be fertile in pretty colours on the calendar. I
suspect I might have purchased a phone intended for female users.
Appaerently the Chinese phone companies sell (so I am told) male and
female orientated mobiles.

Colin
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From forum: PIC - [OT]

Re: Remote network sensors

2008-07-24T17:00:44Z

My client has by some means got a module from

http://www.sena.com/

Initially he baulked at OTS modules but he's come around to my
thinking that at this stage it makes economic sense not to get bogged
down in Ethernet PIC development, but rather concentrate on the
sensor PIC functionality

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From forum: PIC - [PIC]

RE: FET question

2008-07-24T17:00:43Z

something I can think of:

Is your power supply current limited?the gate resistor is way too high for me, but it's not a problem since I assume the load is always on but not switching, right?

another thing is how much current your PIC can give at the output, maybe it's working in linea region or so.

Why not connect your rabbit POSITIVE to the FET source and NEGATIVE to ground? I don't know how it should be working, though.

> From: listas@...> To: piclist@...> Subject: [EE] FET question> Date: Thu, 24 Jul 2008 18:50:41 -0300> > Hi,> I have a circuit with a MOSFET driving a RCM4400W (A Rabbit module> with wifi, that need 80mA on startup and 450mA when the wifi module is on),> and it is not working.> > The power supply is fine, I think, because if I connect the Rabbit> directly to the PSU it works.> > The mosfet seems to be working, because I have 3.3V on the Rabbit> terminals when it is on.> > The FET is driven with a PIC pin with a 5K6 resistor to gate.> > The source of the FET is to GROUND and the drain is connected to the> NEGATIVE terminal of the Rabbit. The POSITIVE terminal of the rabbit is> directly connected to 3.3V.> > There is nothing else in the circuit, shouldn't it be working?> > The FET is an FDV305N, 0.9A and the Vgsth is 1.5V.> > Regards,> > Mauricio Jancic> Microchip Design Partner> Janso Desarrollos> > -- > http://www.piclist.com PIC/SX FAQ & list archive> View/chan
ge your membership options at> http://mailman.mit.edu/mailman/listinfo/piclist
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Re: Getting shinned abroad the arse

2008-07-24T16:56:51Z

I noticed that your toe guard kept falling off. Did you later give
the installer a kick in the arse ?
cc

> On Jul 23, 2008, at 8:11 PM, Tomás Ó hÉilidhe wrote:
>
>
>
> cdb wrote:
>> Well this is getting waaay off topic, but I used to do Karate when I
>> was 18 or so, we didn't wear guards, but I know of someone who broke
>> their toe, by foot connection to the pubis, they were actually aiming
>> for a side kick to the inside of the leg, but sort of got their
>> trajectory wrong.
>
> Might be why Thai's kick exclusively with the shin :-)

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Re: [TECH]:: Why most published research findings are false.

2008-07-24T16:51:19Z

I read this paper and the authors make some pretty amazing leaps of
logic. This does not mean they are wrong and I believe they are
probably right ; still it makes me realize what a cat's bag of
confusion most information packets are these days. Probably for the
past 10,000 years as well.
cc

> On Jul 24, 2008, at 7:28 AM, Matthew Rhys-Roberts wrote:
>
> For further interest, an in relation to the more recent PIClist thread
> regarding mobile phones and cancer, please see also
> http://www.powerwatch.org.uk/science/bias.asp
>
> Matt
>
> Apptech wrote:
>> The claim that 'most published research findings are false',
>> while demonstrably true, is so utterly contrary to intuition
>> and to what we think we know about research methods,
>> statistical analysis and more as to be rejected out of hand
>> by many.
>>
> [snip]
>

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Re: FET question

2008-07-24T16:50:26Z

On Fri, Jul 25, 2008 at 5:50 AM, Mauricio Jancic <listas@...> wrote:

> The FET is driven with a PIC pin with a 5K6 resistor to gate.
>
> The source of the FET is to GROUND and the drain is connected to the
> NEGATIVE terminal of the Rabbit. The POSITIVE terminal of the rabbit is
> directly connected to 3.3V.
>
Like Bob Blick, I do not like to switch the ground side of the Rabbit
either. A better method may be to have the switch in series with
the supply path. An LDO with a shut-down pin will be very good
for this application.

Anyway, I also think 5k6 is too high. The PIC pin may not have
enough driving capability to the FET. Try to reduce 5k6 to lower
value. Or better add a buffer.

Xiaofan
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Dual SIM mobile phone

2008-07-24T16:21:58Z

I'm looking at getting a "dual SIM" mobile phone. I want to be able to
put two SIM cards into the phone, and to be able to have both SIM's
active at the same time. For instance, one minute I might receive a text
to my Irish SIM card, while the next I might receive a phone call on my
Thai SIM card.

Anyone got any experience with these "dual SIM" phones? Are there any
good ones out there?

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Re: Remote network sensors

2008-07-24T16:19:02Z

> Silabs... CP2201-EK (30USD$)

Thanks

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Re: FET question

2008-07-24T16:17:18Z

As an experiment, what happens if you use a relay instead of a FET ?

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RE: FET question

2008-07-24T16:11:38Z

I measured that and there are not voltages drop below 3.2 V. the rabbit
should work down to around 3.15V

Regards,

Mauricio Jancic
Microchip Design Partner
Janso Desarrollos

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Re: Remote network sensors

2008-07-24T16:09:23Z

Hi,

One more:

Silabs... CP2201-EK (30USD$)

Digikey: 336-1316-ND

Luis A P Barbosa

2008/7/22 Jinx <joecolquitt@...>:

> > > "PIC with an Ethernet interface and assignable IP address
>
> > Quickest way to build/program something like this would probably
> > be a serial to ethernet module like an Lantronix X-Port coupled
> > serially to PIC micro doing the sensor interfacing
>
> Thanks. Similar function the Vinculum then
>
>
> http://www.lantronix.com/device-networking/embedded-device-servers/xport.htm
> l
>
> Is there a NZ distributor ? I'm getting only Aussies from Lantronix's
> "Where To Buy"
>
> Approx price for an X-Port ?
>
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Re: FET question

2008-07-24T15:48:11Z

Mauricio,
can you check with a 'scope if the voltage drops momentarily below the
rabbit's lower VDD threshold when the Wireless module turns on? If you have
a DSO, you should be able to set a trigger w/ falling edge at the threshold
voltage.
Regards,
- Marcel

>
> What is puzzling is that with the 5.6 ohm resistor everything works as
> expected, there are 3.3V as needed, but the rabbit won't work.
>
> Regards,
>
> Mauricio Jancic
> Microchip Design Partner
> Janso Desarrollos
>
>
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From forum: PIC - [EE]

Re: Remote network sensors

2008-07-24T15:41:45Z

> says that part # is for Ethernet only, not WiFi.

Comparitive NZ prices for many Lantronix products

http://www.masspar.co.nz/EmBed_Feb_08.pdf#zoom=100

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RE: FET question

2008-07-24T15:38:03Z

> 1) Besides 3.3V and the mosfet drain, what else is connected to the
> rabbit module? (I suspect there may be some kind of ground leakage
> path)

There is no other connection in or out the rabbit. I removed everything to
make tests. The only connections to the Rabbit are the 3.3V line straight
from the MCP1826 voltage regulator and the ground line going from the rabbit
to the GND path through the FDV305N FET.

> 2) What voltage is your PIC running at? (to determine how it is
> driving the FET gate) I assume that the PIC shares the same ground as
> the FET?

Yes, it is the same ground. The everything is running at 3.3V (PIC16F67J10)

> 3) Have you tried measuring the voltage across the rabbit module's
> power input (pos to neg) when the FET is turned on? (trying to
> determine whether there is a static on-resistance problem with the
> FET)

There are 3.3V as expected. The ON time of the FET is 200 uS.

> 4) Does the rabbit module have large capacitors on its input or a
> switching power supply which may have a high inrush current? (This may
> cause the voltage to drop sharply at startup, which may in turn
> trigger the module to shut itself down immediately)

It doesn't seems to. However, it takes 450mA when the wifi module is on. I
know the rabbit works while the wifi is off, but it resets when the power
consumption increases (I should have mentioned this earlier, I know...)

> Also, I'd suggest replacing the rabbit module with a 7 ohm resistor
> (approx) to simulate a 450mA load, then turn on your FET and measure
> how much voltage there is across the FET and across the resistor.

I've done it with a 5.6 ohm. The weird thing is that it works just fine
(550+ mA). With the actual load (the rabbit) the PIC resets sometimes when
it is turned on, the 5.6ohm resistor has no negative effect however.

> You might also try removing the 5.6K resistor and just driving the FET
> gate directly from the PIC.

Donne that. This causes the PIC to reset as soon as the GATE line is taken
high. I put the resistor to solve this. I also placed a 1000 uF capacitor in
the output of the MCP1826 voltage regulator, to improve this reset problem,
that I trace down to the regulator not being able to regulate on the sudden
change of load.

What is puzzling is that with the 5.6 ohm resistor everything works as
expected, there are 3.3V as needed, but the rabbit won't work.

Regards,

Mauricio Jancic
Microchip Design Partner
Janso Desarrollos

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From forum: PIC - [EE]

Re: Remote network sensors

2008-07-24T15:30:38Z

On Thu, Jul 24, 2008 at 2:53 PM, Marcel Duchamp
<marcel.duchamp@...> wrote:

> Alex Harford wrote:
>
>> Hmm... Lantronix WiPorts are $119 each. You can get a Linksys WRT54GL
>> (Linux version), and solder on a 2x?? (10 I think) header to give you
>> 2 serial ports. Kernel modules are available for GPIO bit banging, to
>> access SD cards via SPI, etc.
>>
>> http://www.newegg.com/Product/Product.aspx?Item=N82E16833124190
>>
>> Probably doesn't work for a finished product, but might do the trick
>> for a prototype.
>
>
> ...or maybe get this one at $29.95:
>
> http://www.mouser.com/Search/ProductDetail.aspx?qs=ZvDUiWN9X0296qs4drWfQQ%3d%3d

Is it just me, or is that miscategorized? Specs page here:
http://www.lantronix.com/device-networking/embedded-device-servers/xport-direct.html

says that part # is for Ethernet only, not WiFi.
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From forum: PIC - [PIC]

Re: Remote network sensors

2008-07-24T15:17:19Z

Marcel Duchamp wrote:
> Alex Harford wrote:
>

uh, never mind! Just noticed Alex specified "WiPorts" which the part
below is not. Doh.

>
> ...or maybe get this one at $29.95:
>
> http://www.mouser.com/Search/ProductDetail.aspx?qs=ZvDUiWN9X0296qs4drWfQQ%3d%3d

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From forum: PIC - [PIC]

Re: Remote network sensors

2008-07-24T15:16:50Z

> ...or maybe get this one at $29.95:

http://www.lantronix.com/pdf/XPort-Direct_PB.pdf

Worth some very serious consideration indeed

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From forum: PIC - [PIC]

Re: The physics of stuff getting hit

2008-07-24T15:15:21Z

FWIW:
Last I heard aircraft certification required windshields be tested to not
break with a four pound bird strike at cruise speed.

That may not be true because the rest of the story claimed that a company
suddenly could not pass the test. It turned out that the Quality Control
folks reduced their expenses by switching to frozen chickens for the test.
Returning to fresh chickens resolved the problem.

John Ferrell W8CCW

"All that is necessary for the triumph of evil is for good men to do
nothing." -- Edmund Burke
http://DixieNC.US

----- Original Message -----
From: "Tomás Ó hÉilidhe" <toe@...>
To: "Microcontroller discussion list - Public." <piclist@...>
Sent: Wednesday, July 23, 2008 7:10 PM
Subject: [OT] The physics of stuff getting hit

>
> What kind of units do you use in physics to describe how hard a smack
> something got, or how hard a smack something can sustain?
>
> I mean let's say you're selling tripple-glazed windows, and you're
> marketing them as being "virtually indestructible". Your ad for them
> might say that they can sustain a smack as high as 400 neckles. I'm just
> wondering what a "neckle" would be? Would it be force? Or pressure? Or
> impulse?

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From forum: PIC - [OT]

Re: FET question

2008-07-24T15:08:29Z

Hi Mauricio,

A few questions:

1) Besides 3.3V and the mosfet drain, what else is connected to the
rabbit module? (I suspect there may be some kind of ground leakage
path)
2) What voltage is your PIC running at? (to determine how it is
driving the FET gate) I assume that the PIC shares the same ground as
the FET?
3) Have you tried measuring the voltage across the rabbit module's
power input (pos to neg) when the FET is turned on? (trying to
determine whether there is a static on-resistance problem with the
FET)
4) Does the rabbit module have large capacitors on its input or a
switching power supply which may have a high inrush current? (This may
cause the voltage to drop sharply at startup, which may in turn
trigger the module to shut itself down immediately)

Also, I'd suggest replacing the rabbit module with a 7 ohm resistor
(approx) to simulate a 450mA load, then turn on your FET and measure
how much voltage there is across the FET and across the resistor.

You might also try removing the 5.6K resistor and just driving the FET
gate directly from the PIC.

Sean

On Thu, Jul 24, 2008 at 5:50 PM, Mauricio Jancic <listas@...> wrote:

> Hi,
> I have a circuit with a MOSFET driving a RCM4400W (A Rabbit module
> with wifi, that need 80mA on startup and 450mA when the wifi module is on),
> and it is not working.
>
> The power supply is fine, I think, because if I connect the Rabbit
> directly to the PSU it works.
>
> The mosfet seems to be working, because I have 3.3V on the Rabbit
> terminals when it is on.
>
> The FET is driven with a PIC pin with a 5K6 resistor to gate.
>
> The source of the FET is to GROUND and the drain is connected to the
> NEGATIVE terminal of the Rabbit. The POSITIVE terminal of the rabbit is
> directly connected to 3.3V.
>
> There is nothing else in the circuit, shouldn't it be working?
>
> The FET is an FDV305N, 0.9A and the Vgsth is 1.5V.
>
> Regards,
>
> Mauricio Jancic
> Microchip Design Partner
> Janso Desarrollos
>
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> http://mailman.mit.edu/mailman/listinfo/piclist
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From forum: PIC - [EE]

Re: FET question

2008-07-24T15:07:13Z

Hi Mauricio,

Although switching the ground side of the Rabbit might not be how I
would do it, it is probably OK. But only if you make sure that you are
not driving any of the Rabbit pins with 0 volts when the Rabbit is
unpowered. This can cause latchup and also other weird stuff.

I have found that chips are more sensitive to latchup when driven
negative than positive. But that is just my personal observation.

An example of weird stuff that isn't latchup is an LM324 opamp when
inputs are driven below the negative supply, it creates huge output
swings.

Cheerful regards,

Bob

On Thu, 24 Jul 2008 18:50:41 -0300, "Mauricio Jancic"
<listas@...> said:

> Hi,
> I have a circuit with a MOSFET driving a RCM4400W (A Rabbit module
> with wifi, that need 80mA on startup and 450mA when the wifi module is
> on),
> and it is not working.
>
> The power supply is fine, I think, because if I connect the Rabbit
> directly to the PSU it works.
>
> The mosfet seems to be working, because I have 3.3V on the Rabbit
> terminals when it is on.
>
> The FET is driven with a PIC pin with a 5K6 resistor to gate.
>
> The source of the FET is to GROUND and the drain is connected to the
> NEGATIVE terminal of the Rabbit. The POSITIVE terminal of the rabbit is
> directly connected to 3.3V.
>
> There is nothing else in the circuit, shouldn't it be working?
>
> The FET is an FDV305N, 0.9A and the Vgsth is 1.5V.

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