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Electron | 9 Feb 19:17
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Re: [EE] amplifier for variable reluctance sensor

At 10.06 2012.02.09, you wrote:
>> I need to design a device that interfaces to the speed sensor of heavy
>> trucks. These are variable reluctance sensors and will remain connected
>> to the vehicle's ECU, my circuit will piggyback. These are two-wire,
>> differential signals full of common-mode noise and vary in amplitude
>> greatly with frequency and also position as the tailshaft bearing wears
>> in the vehicle.
>
>I had a similar but totally different [tm] application whose solution
>may be your solution.
>
>I had a variable speed alternator (exercise machine load) whose out
>put was a low voltage sinusoid at low speeds but which soon chose to
>flat topped trapezoids clamped to the mean load voltage. As this
>voltage varied depending on speed and net absolute load desired it
>would have been modestly challenging to speed sense from. Now add 10
>kHz PWM that takes a fixed resistor and PWM's it across the rectified
>alternator output to change the effective resistance seen by the
>alternator. Yee ha.
>
>After trying all sorts of things I was offended by the simplicity of
>what proved to be a superb solution.
>Stops to find a circuit from about 10 years  ago ...
>.... Found ...
>Hmmm. May 18th 2006. More recent than I would have thought.
>
>2 x BC337 or whatever
>Differential long tailed pair.
>100k collector resistor per transistor.
>Join emitters with 1k to ground,
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Electron | 9 Feb 17:38
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Re: [EE] amplifier for variable reluctance sensor


But when we talk about differential sensor, we mean 3 wires, right?
I mean, not only the two complementary signals, but a ground MUST be
there, else it won't be a differential sensor.. am I right?

Cheers,
Mario

At 17.02 2012.02.09, you wrote:
>I would consider using a decent-quality audio transformer for 
>isolation into your circuit.  That means that you can use a normal 
>single-ended (not differential) amplifier for signal conditioning.
>
>The transformers that I use are a semi-custom part (standard part 
>number but manufactured when the order is placed) that I purchase in 
>thousands.  They are relatively small (similar in size to Mouser's 
>TM016) but with super high inductance and darned decent low-frequency 
>response.  Provided that your amplifier has relatively high input 
>impedance, the truck's sensor and electronics should not even notice 
>the addition of your circuit.
>
>I'd be happy to send you a couple of transformers for you to try and 
>I can supply as many as you need, up to the point where your 
>quantities justify you ordering them yourself.
>
>Something like Mouser's TM016 is most likely NOT suitable because the 
>inductance is fairly low - the low frequency response of those 
>transformers is rated at 200Hz when fed with a 600R source.  They are 
>OK for telco-type circuits but not for Hi-Fi audio and certainly not 
>for a variable-reluctance sensor where the speed approaches zero.
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David VanHorn | 9 Feb 17:18
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[EE] Arduino stuff

Suffering with low signal to noise ratio on gargoyle and the innertubes..

I am looking for a couple of key components, they don't have to be
"shields", but they do have to play well with others.

1: Instrumentation amp suitable for EMG sorts of signals.

2: Power supply, variable output controlled by the processor, 0-50VDC.

I don't have an issue with designing these, but if they already exist
and aren't big $, I'd rather buy them.
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Dwayne Reid | 9 Feb 17:02
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Re: [EE] amplifier for variable reluctance sensor

I would consider using a decent-quality audio transformer for 
isolation into your circuit.  That means that you can use a normal 
single-ended (not differential) amplifier for signal conditioning.

The transformers that I use are a semi-custom part (standard part 
number but manufactured when the order is placed) that I purchase in 
thousands.  They are relatively small (similar in size to Mouser's 
TM016) but with super high inductance and darned decent low-frequency 
response.  Provided that your amplifier has relatively high input 
impedance, the truck's sensor and electronics should not even notice 
the addition of your circuit.

I'd be happy to send you a couple of transformers for you to try and 
I can supply as many as you need, up to the point where your 
quantities justify you ordering them yourself.

Something like Mouser's TM016 is most likely NOT suitable because the 
inductance is fairly low - the low frequency response of those 
transformers is rated at 200Hz when fed with a 600R source.  They are 
OK for telco-type circuits but not for Hi-Fi audio and certainly not 
for a variable-reluctance sensor where the speed approaches zero.

dwayne

At 12:29 PM 2/8/2012, Bob Blick wrote:
>I need to design a device that interfaces to the speed sensor of heavy
>trucks. These are variable reluctance sensors and will remain connected
>to the vehicle's ECU, my circuit will piggyback. These are two-wire,
>differential signals full of common-mode noise and vary in amplitude
>greatly with frequency and also position as the tailshaft bearing wears
(Continue reading)

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John Ferrell | 9 Feb 15:12
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[OT]: Raspberry Pi

If you have an interest in the Raspberry Pi Project and its inner 
workings you may want to download this 205 page PDF that was referenced 
on Slashdot.

http://dmkenr5gtnd8f.cloudfront.net/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf

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government we're paying for. - Will Rogers

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Tamas Rudnai | 9 Feb 12:50
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[OT] Matternet - "Internet" for transporting material

Recently there was a discussion about UAV, this one is somewhat related to
that.

Brazil is building a network of small UAV fleet for distributing vital
drugs and possible other material:
http://www.youtube.com/watch?v=7B3E4OOuGDk

Official page for the project:
http://matternet.net/

Tamas
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Electron | 8 Feb 17:16
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RE: [EE] increasing sensitivity of a thermistor

At 12.12 2012.02.08, you wrote:
>
>
>> -----Original Message-----
>> From: piclist-bounces <at> mit.edu [mailto:piclist-bounces <at> mit.edu] On Behalf
>> Of alan smith
>> Sent: 07 February 2012 20:37
>> To: Microcontroller discussion list - Public.
>> Subject: [EE] increasing sensitivity of a thermistor
>> 
>> hi group..me again
>> 
>> I want to bounce something off the members.
>> 
>> 
>> So I have a board that I designed with a 10K
>> thermistor, but its feeding a 3.3V micro (and that is fixed...cant change
>> this
>> part).  They have come back and asked for
>> a better resolution.
>> 
>> Now a thermistor, it simply generates a voltage
>> as a divider with a source impedance of course.  As the temperature
>> changes, the voltage that
>> is
>> generated across it changes, and the resolution
>> of what you can measure is going to be dependent on the source voltage as
>> well
>> as the ADC resolution.
>>
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Electron | 9 Feb 12:17
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Re: [PIC] help with adc on dspic30F4011

At 18.12 2012.02.08, you wrote:
>Thank you both, Mario and Alan.
>
>I checked errata for 30f4011 and discovered it has "lots" of "bugs", my
>next micro will be a 33F or 33EP (I love 33EP256MU806 specs for a 64 pin
>micro).
>
>It is not possible to do AD conversions at 1 Msps due to bugs, max is 750
>ksps.
>
>After inspection of assembly output from my C compiler, I discovered it was
>setting SAMC and ADCS in ADCON3 register at its maximum values (SAMC=11111
>"31 Tad" and ADCS=111111 "32 Tcy"). That was the reason of its slow speed.
>Now, lowering this values I speeded it up a lot. I have to check for
>integrity of data at that speed, but looks promissing and more acceptable.
>
>I still have a lot of doubts, but the increase of speed makes me happy and
>do not need to dig more into the question by the moment.
>
>Thanks again.

You're welcome.

I just stumbled upon another problem, but on a PIC32MX1XX: when I enabled
compiler optimizations, the ADC results looked buggy. In the end, as I am
using autosampling, I had to put at least a NOP or a DONE=0 between the line
with SAMP=1 and the loop where I check if DONE became 1. I found the "bug"
as I had suspected in the past that this would be necessary, however the
documentation didn't specify it was, so I omitted the extra code. Now I
know it was due.. it happens very rarely that the loop get skipped as it
(Continue reading)

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David | 8 Feb 22:36

[PIC] Extra current after sleeping

All,

I have a very simple app for an 18F but this is the first time I have
used sleep mode or paid close attention to current consumption.  It is
battery powered and I'd like it to last as long as possible.

The board has a number of peripherals (a SHT temp/humidity sensor, MPL
pressure sensor, RTC and a RFM radio module).  However I am almost
positive that none of these are the cause of my problem, after a lot of
debugging.

The basic control flow is:

- initialise peripherals
- set RTC to give a 1 minute alarm interrupt
- configure falling edge interrupt on the RTC interrupt pin
- enter while(1) loop (application code will be here)
- sleep

The ISR just clears the interrupt, I have slimmed down the code
completely to isolate the bug.

The first time it enters sleep the current drawn from the battery drops
below 1mA, to 0.01mA on my meter (which probably be inaccurate, it's a
$5 special).  When it wakes the first time it spikes briefly and then
drops to ~2.5mA on the second sleep.  It never drops below 2.5mA again,
this is completely reproducible.

The only peripherals powered on during sleep are the RTC and the radio.
 The radio is definitely in its own sleep mode as otherwise it uses
(Continue reading)

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Bob Blick | 8 Feb 22:20
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[EE] Re: Tips for hand routing boards?

forwarding with tag added

On Wed, Feb 8, 2012, at 03:59 PM, Marc Nicholas wrote:
> Hi all,
> 
> Does anyone have any "tricks of the trade" for hand routing boards?
> Specifically, hand routing from reasonably high density TQFP/QFN parts
> (44
> and 64-pin) in 6 to 8-mil to other lower density components (think hub
> and
> spoke).
> 
> I'm getting beyond the stage where Eagle's autorouter does a good job...
> 
> Appreciated in advance.
> 
> -m

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Bob Blick | 8 Feb 20:29
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[EE] amplifier for variable reluctance sensor

I need to design a device that interfaces to the speed sensor of heavy
trucks. These are variable reluctance sensors and will remain connected
to the vehicle's ECU, my circuit will piggyback. These are two-wire,
differential signals full of common-mode noise and vary in amplitude
greatly with frequency and also position as the tailshaft bearing wears
in the vehicle.

Right now I am designing the front end and would love to use something
like the MAX9924 since it makes things simple. But it's a Maxim part
which I am still hesitant to spec.

Parts like the LM1815, LM2907, NCV1124 are all single-ended input. The
NCV7001 is end-of-life.

Any pointers toward a differential VR sensor interface IC?

This is a smallish volume product, so I don't expect to be able to get
any high-volume ABS interface parts. Which at this point are probably so
highly integrated with other functions as to be unusable to repurpose
for my use anyway.

Thanks,

Bob

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Gmane