HighPressureLogger ... Re: Which protocol to implement on a home brewed diving computer ?

Tue Mar 17 08:01:37 PDT 2015

Betreff: 	HighPressureLogger ... Re: Which protocol to implement on a 
home brewed diving computer ?
Datum: 	Tue, 17 Mar 2015 15:58:09 +0100
Von: 	Thomas Schrein (mailinglists) <tsx508 at schrein.de>
An: 	Robert Helling <helling at atdotde.de>

Am 17.03.2015 um 11:48 schrieb Robert Helling:
> Hi,
>
>> On 17.03.2015, at 11:33, Thomas Schrein (mailinglists) 
>> <tsx508 at schrein.de <mailto:tsx508 at schrein.de>> wrote:
>>
>> One option (may be you better say vision ;-) in our project is to use 
>> the odico electronics to control a rebreather using CANBUS (the 
>> controller has it build in already) and therefore the high pressure 
>> sensor would act as an CANBUS node with its own buildin controller, 
>> in particular a STMF1x, less then 5€ each.  The electronics could be 
>> sealed with casting resin.
>> For our rebreather approach we accept the existence of wires, so we 
>> don't need to care about energy and communication. The pressure 
>> sensors cost about 80€, plus the adapter for the high pressure, plus 
>> the wiring, but that costs are not a big deal to run a rebreather.
>> My fellow, Marco, also doesn't care to much building even an self 
>> made pressure sensor with build in electronics . He has a degree as 
>> mechanical engineer and he's really gifted for job!
>> So we don't care too much to get it water tight.
>>
>> From my point of view a logger could be designed like this:
>> - located at the high pressure hole of the first stage
>> - length about 5 - 10 cm, cylindrical
>> - collecting data for pressure + time
>> - as an option: collection depth+temp
>> - energy by an AAA or 1/2 AA lithium 3v cell than could be replaced 
>> once a year
>> - communication via radio (bluetooth, ...)
>> - shop price < 200 €
>
> 80 Euros for the sensor sound like a good price. May I ask which 
> sensor this is?
http://www.automation24.de/prozesssensoren/elektronischer-drucksensor-automation24-pc6706-i10-374-0.htm

> When I did my research I found that you can buy sensors that already 
> have the correct fitting to go into the HP port of a first stage (UNF 
> 7/16”).
Where can I get it ?
> For prototyping the logger I would have started with something like 
> http://www.exp-tech.de/sparkfun-logomatic-v2-serial-sd-dataloger-fat32 That 
> has everything including battery recharging logic (and is a USB mass 
> storage device).
Looks good for prototyping. I would take a SD device only if I wanted to 
use the SD card for the data transfer to the PC. They burn about 100mA, 
lot more than the processor itself. I wourld prefer SPI FLASH.

As said, we will connect that sensor to our already existing housing 
(odico) and will go diving, the logging function is only a subset of the 
odico functions. So its hard to me to plan for logger an extra 
prototype/proof of concept.

Our next steps would be more focussed in
1. integrate the highpressure piezo sensor into a selfmade housing
2. build a prototype with an EAGLE designed PCB that fits in a size < 10cm

What about communication? USB / radio ?
Energy ? Rechargeable or change of the cell ?

Tom

>
> Best
> Robert
>
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> Robert C. Helling     Elite Master Course Theoretical and Mathematical 
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