> Power availability is not an issue, although there is an overall
> limit to about 2-5 watts, and a very clean power bus is
> anticipated.  HOWEVER, there is a requirement for operation in a
> Class-I, Div-1 or Div-2 explosive environment.  i.e. intrinsic safety
> is mandatory, which implies low voltage and low power requirements,
> along with high immunity to EMI, ESD, and gross over-voltage
> conditions.  Energy storage devices such as inductors and capacitors
> must be minimized almost to the point of non-existence compared to
> normal consumer applications, which can create issues for
> bypassing  and filtering electronic noise ;-).
>

> I was asked to post this for a buddy, but it is serious money, if the quote
> is accepted. Please reply offlist to me? Thank you!
>
> Basically, he wants to find an ready to roll CAN bus project with EVERYTHING
> needed to read a few sensors in a car, do some processing on those reading
> with some microcontroller (PIC? MSP430? AVR? Whatever) and then post out
> messages to some device on the bus that will do something with the
> information. Yeah... not a great spec, but the point is to just find a
> development system that already has the standard stuff in it for working
> with things you find in a car so we don't have to burn all the cycles
> required to come up to speed on it.
>
> Here are the details we have so far:
>
> PROJECT #1:  Automotive Sensor System  (HOT!--RFQ response due this
> coming Monday, Product by mid-March)
>
> Basic requirements are for an automotive environment (with ALL that
> implies for temperature, shock, vibration, MTBF, etc.!) sensor/signal
> conditioner/CAN transceiver module.  We already have the sensor suite
> and signal conditioners as COTS products which will require minimal
> modification.  We are looking for a recommended chip set and
> benchmark design that provides the ADC and CAN interface and
> processor.  The sensor suite will provide several (typically 2, but
> potentially up to 8) analog signals which will need to be digitized,
> and processed through a 2-3 element polynomial equation to generate a
> temperature compensated and linearized output value for each
> sensor.  It may also be possible to move the processing to the
> control module and merely report measured values if there are
> significant savings in cost or space. Overall accuracy can be met
> with a 12-bit ADC, although higher resolution is MUCH preferred.
>
> Although we have not yet seen the customer's CAN specification, it is
> believed to meet normal American and European automotive
> requirements, and have a relatively simple command/response
> set.  Evenutally the system will require EU, CE, FCC, and other
> approvals.  ROHS is also required.
>
> Power availability is not an issue, although there is an overall
> limit to about 2-5 watts, and a very clean power bus is
> anticipated.  HOWEVER, there is a requirement for operation in a
> Class-I, Div-1 or Div-2 explosive environment.  i.e. intrinsic safety
> is mandatory, which implies low voltage and low power requirements,
> along with high immunity to EMI, ESD, and gross over-voltage
> conditions.  Energy storage devices such as inductors and capacitors
> must be minimized almost to the point of non-existence compared to
> normal consumer applications, which can create issues for
> bypassing  and filtering electronic noise ;-).
>
> Full galvanic isolation of the sensors and processor from the CAN bus
> may be an additional requirement imposed by the sensors.  There are
> several good digital isolation solutions available, and we do not
> anticipate problems here.
>
> Although this requirement is being driven by a specific customer, we
> want to end up with a "generic" system that can be easily adapted to
> different sensor suites and applications in the future.
>
>
> James Newton: PICList webmaster/Admin
> .....jamesnewtonKILLspam.....piclist.com  1-619-652-0593 phone
> http://www.piclist.com/member/JMN-EFP-786
> PIC/PICList FAQ: http://www.piclist.com
>
>

> On 1/4/08, James Newton <EraseMEjamesnewtonspam_OUTTakeThisOuTmassmind.org> wrote:
> > PROJECT #1:  Automotive Sensor System  (HOT!--RFQ response
> > due this coming Monday, Product by mid-March)
>
> This does not correlate well with the followed requirement of
> IS (intrinsic safety) which is a long process and not many
> people are in this field. You need a standard expert to guide
> you on the design.
>
> > Power availability is not an issue, although there is an overall
> > limit to about 2-5 watts, and a very clean power bus is
> > anticipated.  HOWEVER, there is a requirement for operation in a
> > Class-I, Div-1 or Div-2 explosive environment.  i.e. intrinsic safety
> > is mandatory, which implies low voltage and low power requirements,
> > along with high immunity to EMI, ESD, and gross over-voltage
> > conditions.  Energy storage devices such as inductors and capacitors
> > must be minimized almost to the point of non-existence compared to
> > normal consumer applications, which can create issues for
> > bypassing  and filtering electronic noise ;-).
> >
>
> I have only done two projects with EEx ia (Intrinisic safety) so
> I am not an expert. But I know that the domain knowledge of
> intrinsic safety is very specific. The certification can take a long
> time. Certification related testing can be quite long as well.
>
> By the way, Pepperl+Fuchs (my previous employer) is the
> leading Intrinsic Safety vendor along with MTL (a UK company).
>
> Xiaofan

>> We are looking for a recommended chip set and benchmark
>> design that provides the ADC and CAN interface and
>> processor.  The sensor suite will provide several (typically 2, but
>> potentially up to 8) analog signals which will need to be digitized,
>> and processed through a 2-3 element polynomial equation to generate
>> a temperature compensated and linearized output value for each
>> sensor.  It may also be possible to move the processing to the
>> control module and merely report measured values if there are
>> significant savings in cost or space. Overall accuracy can be met
>> with a 12-bit ADC, although higher resolution is MUCH preferred.

>From the requirement, the sensor will reside in Division 1. If the

>> Energy storage devices such as inductors and capacitors
>> must be minimized almost to the point of non-existence compared to
>> normal consumer applications, which can create issues for
>> bypassing  and filtering electronic noise ;-).
>
> I can understand certain types of capacitors, but what do you have against
> small inductors?  These are very reliable and safe, since they are basically
> rolled up wire and a chunk of reasonably inert magnetic material.  A well
> designed switching power supply on the input seems to me the safest choice.
> The reduced need for cooling alone will simplify and safefy (;-)) things
> compared to alternatives.

>> Full galvanic isolation of the sensors and processor from the CAN bus
>> may be an additional requirement imposed by the sensors.
>
> You need to decide the "may" part.  As I'm sure you understand, that makes
> quite a difference in the design.
>
>> There are
>> several good digital isolation solutions available, and we do not
>> anticipate problems here.
>
> Not so fast.  12 bit accuracy accross galvanic isolation means shipping
> power to the isolated side, converting there, and shipping digital values
> back.  While this is all doable, it does take power, parts, board space, and
> $$.
>
>> Although this requirement is being driven by a specific customer, we
>> want to end up with a "generic" system that can be easily adapted to
>> different sensor suites and applications in the future.
>
> That makes sense given the overall "development board" flavor.  You think
> you want is a platform for testing concepts and proving viability and as a
> reference design for resulting products.  This unit is not intended to be
> the product?
>
> To get to a real spec there will need to be some serious interactive
> discussion with the people that truly understand the requirements and are in
> a position to make tradeoffs when choices are presented.  Often these people
> know that they want, but don't realize all the ways the results could be
> achieved and how seemingly small changes in the requirements can make big
> differences to the implementation.  A interactive discussion between those
> that know what they want and a engineer that knows the implementation
> tradeoffs is necessary for a good result for everyone.  You need to provide
> a phone number and a good time to call.

> > Energy storage devices such as inductors and capacitors
> > must be minimized almost to the point of non-existence compared to
> > normal consumer applications, which can create issues for
> > bypassing  and filtering electronic noise ;-).
>
> I can understand certain types of capacitors, but what do you have against
> small inductors?  These are very reliable and safe, since they are basically
> rolled up wire and a chunk of reasonably inert magnetic material.  A well
> designed switching power supply on the input seems to me the safest choice.
> The reduced need for cooling alone will simplify and safefy (;-)) things
> compared to alternatives.

> > Full galvanic isolation of the sensors and processor from the CAN bus
> > may be an additional requirement imposed by the sensors.
>
> You need to decide the "may" part.  As I'm sure you understand, that makes
> quite a difference in the design.
>
> > There are several good digital isolation solutions available, and we do not
> > anticipate problems here.
>
> Not so fast.  12 bit accuracy accross galvanic isolation means shipping
> power to the isolated side, converting there, and shipping digital values
> back.  While this is all doable, it does take power, parts, board space, and
> $$.

> There are two parts to that, as far as I can see:
>
> 1. The design has to be I.S.
>
> 2. The design has to be certified I.S.
>
> Is the first part something that can be reasonable accomplished for a few
> grand? And then the second part costs the big bucks? Or is it that an I.S.
> design is going to have to be guided by top dollar people and/or use top
> dollar parts?
>

> So what I'm hearing is that the CAN bus stuff is no big deal, or at least
> that there are some off the shelf resources available for it, but the
> "Intrinsic Safe" part is a real killer.
>
> There are two parts to that, as far as I can see:
>
> 1. The design has to be I.S.
>
> 2. The design has to be certified I.S.
>
> Is the first part something that can be reasonable accomplished for a few
> grand? And then the second part costs the big bucks? Or is it that an I.S.
> design is going to have to be guided by top dollar people and/or use top
> dollar parts?
>
> --
> James.
>