Moninos: Sacre bleu- your English better than mine! Welcome to the Forum & bravo on your astute observations. I'll leave it to others to respond, but inform that the original poster is the captain - one of two in fact (they have rotating month on/month off duties). Stan. in RWC mad NZ ("Allez les All Blacks")
Massive project for temp. and i just heard of picaxe
- Thread starter bullethead67
- Start date
@Mininos, See post #65 (on page 7) for the prototype specification.
The ultimate goal is increased serviceability due to prompt reliable bearing temperature information.
The main bearings (56) have their temperature recorded hourly. The task is performed by a junior rating and offers little in the way of job satisfaction, the schedule is tight with not a lot of opportunities for a relaxing refreshment breaks, so the recorded information is believed to occasionally be unreliable due to the vagaries of human nature.
This can result in an abnormal temperature reading being missed for potentially a number of hours in which time a fault might become a little more serious than if it had been caught correctly in the hourly inspection, which remains an operational requirement.
The proposed project should increase both the reliability and frequency of data available to the Master and other personnel on the bridge. The requirement is for a three LED display per bearing; cold, warm(normal) and hot. Senior Engineers want to see numbers to better understand the severity of a problem of a failing bearing. Buy in by such people is important to the project being acceptable to the company. If you can't convince the relevant officers of the crew, then the jig is up before it has begun.
It is my opinion that RS485 using COTS (Common Off The Shelf) devices is the safest communication option involving least risk in the available timescale.
This is subject to certain caveats as the basic standard allows a maximum 32 nodes on a bus and with all transmitters on the bus the state of receivers is not defined which in an electrically noisy environment might give rise to spurii . However there are many RA485 device manufacturers in the market place today selling devices with failsafe features (receivers default to mark high condition if all transceivers on the bus are in their high impedance state) and capable of 64, 128 or more commonly 256 nodes per bus as standard and with enhanced devices with 60V fault tolerance, 5kV ESD protection and even galvanic isolation between system and line sides of the device. Available in 5V and 3.3V versions.
I understand that the DS18B20 device has been agreed as the temperature sensor of choice, although LM35 and NTC thermistors offer cheaper but less flexible options.
I'm personally waiting for Bullethead67 to finish his off duty break and return to the thread as it is his project and he will be needing advice which I am eager to listen to, but am probably not sufficiently qualified to give myself. I do have areas of competence, but not alas expertise.
The basic system showing the status of all bearings as blue, green or red on a display board is very useful in itself, but there are a number of enhancements over and above the basic model that can be made.
Shielded cable? The RS485 receivers are differential and common mode interference is self cancelling. Just like the telephone UTP cable (I assume).
75 metres is a long way. RS485 is good for 1200m.
With intervals of 5 and 10 minutes between each set of new readings that's 5 or 11 more readings than the current system offers, with a potentially greater honesty factor.
The ultimate goal is increased serviceability due to prompt reliable bearing temperature information.
The main bearings (56) have their temperature recorded hourly. The task is performed by a junior rating and offers little in the way of job satisfaction, the schedule is tight with not a lot of opportunities for a relaxing refreshment breaks, so the recorded information is believed to occasionally be unreliable due to the vagaries of human nature.
This can result in an abnormal temperature reading being missed for potentially a number of hours in which time a fault might become a little more serious than if it had been caught correctly in the hourly inspection, which remains an operational requirement.
The proposed project should increase both the reliability and frequency of data available to the Master and other personnel on the bridge. The requirement is for a three LED display per bearing; cold, warm(normal) and hot. Senior Engineers want to see numbers to better understand the severity of a problem of a failing bearing. Buy in by such people is important to the project being acceptable to the company. If you can't convince the relevant officers of the crew, then the jig is up before it has begun.
It is my opinion that RS485 using COTS (Common Off The Shelf) devices is the safest communication option involving least risk in the available timescale.
This is subject to certain caveats as the basic standard allows a maximum 32 nodes on a bus and with all transmitters on the bus the state of receivers is not defined which in an electrically noisy environment might give rise to spurii . However there are many RA485 device manufacturers in the market place today selling devices with failsafe features (receivers default to mark high condition if all transceivers on the bus are in their high impedance state) and capable of 64, 128 or more commonly 256 nodes per bus as standard and with enhanced devices with 60V fault tolerance, 5kV ESD protection and even galvanic isolation between system and line sides of the device. Available in 5V and 3.3V versions.
I understand that the DS18B20 device has been agreed as the temperature sensor of choice, although LM35 and NTC thermistors offer cheaper but less flexible options.
I'm personally waiting for Bullethead67 to finish his off duty break and return to the thread as it is his project and he will be needing advice which I am eager to listen to, but am probably not sufficiently qualified to give myself. I do have areas of competence, but not alas expertise.
The basic system showing the status of all bearings as blue, green or red on a display board is very useful in itself, but there are a number of enhancements over and above the basic model that can be made.
Shielded cable? The RS485 receivers are differential and common mode interference is self cancelling. Just like the telephone UTP cable (I assume).
75 metres is a long way. RS485 is good for 1200m.
With intervals of 5 and 10 minutes between each set of new readings that's 5 or 11 more readings than the current system offers, with a potentially greater honesty factor.
Last edited:
@Mpep,
I think that you first muted RS485 - my research I find has a lot of enhanced devices on the market today with some mfrs coming in with failsafe, 256nodes at around entry level pricing whilst others offer the same technology as their enhanced products. I particularly like the LTC1487 from Linear Technology (low EMI version). In fact Rapid here in the UK have discontinued the 8DIP package and the 8SOIC package is available until stock runs out. Not having circuit board facilities it's a bit of a bummer, but will be buying in ten 8SOIC for mounting dead bug fashion, impressed by the spec at the price. I will also buy at a slightly lesser price a couple of SIpex SP485CN (bog standard spec). I have learned a lot since I last really looked at RS422 20+ years ago. Thank you.
My own application is smaller and not rigerous, to monitor a couple of beehives, but I just helped a friend put 114 hives into one apiary to overwinter - now that would be interesting (futile perhaps)!
Back to the subject:
Post #3
Temp Range
The temp range would be around 15 to 100 C
. . .
and yes I do want 1 temp sensor per bearing and 1 led indicator per bearing.
Post #64
What is hot?
there is disagreement on this too. appx 140 is getting hot and 170 is really hot. 200 is cooked. ill need to contact Cooper bearing and get a specific range.
I am assuming the latter figures are degrees Fahrenheit, based upon the post #3 estimate and the use of Fahrenheit by the crew. this was mentioned earlier as the vessel is US registered and has a US crew.
They are happy with that, it's the bearings that they don't want U/S
Big advantage to the DS18B20 is that it's directly supported by the Picaxe firmware. The LM95172 would present interface problems as it is unlikely to use the OneWire protocol used by readtemp. If it was effecively a drop in replacement at the right price It might be attractive.
I can find no regular local supplier here in the UK and the best price I seem to be able to come up with is around 27 USD.
http://www.findchips.com/avail/?part=LM95172&partner=DS4U&utm_source=DS4U&utm_medium=Link
Your go . . . I remain to be convinced about the code to handle this device, suitable suppliers (anywhere) and a reasonable price.
Honest, I'm only an advocate and not the Devil . . . Difficult to tell at times though!
I think that you first muted RS485 - my research I find has a lot of enhanced devices on the market today with some mfrs coming in with failsafe, 256nodes at around entry level pricing whilst others offer the same technology as their enhanced products. I particularly like the LTC1487 from Linear Technology (low EMI version). In fact Rapid here in the UK have discontinued the 8DIP package and the 8SOIC package is available until stock runs out. Not having circuit board facilities it's a bit of a bummer, but will be buying in ten 8SOIC for mounting dead bug fashion, impressed by the spec at the price. I will also buy at a slightly lesser price a couple of SIpex SP485CN (bog standard spec). I have learned a lot since I last really looked at RS422 20+ years ago. Thank you.
My own application is smaller and not rigerous, to monitor a couple of beehives, but I just helped a friend put 114 hives into one apiary to overwinter - now that would be interesting (futile perhaps)!
Back to the subject:
Post #3
Temp Range
The temp range would be around 15 to 100 C
. . .
and yes I do want 1 temp sensor per bearing and 1 led indicator per bearing.
Post #64
What is hot?
there is disagreement on this too. appx 140 is getting hot and 170 is really hot. 200 is cooked. ill need to contact Cooper bearing and get a specific range.
I am assuming the latter figures are degrees Fahrenheit, based upon the post #3 estimate and the use of Fahrenheit by the crew. this was mentioned earlier as the vessel is US registered and has a US crew.
They are happy with that, it's the bearings that they don't want U/S Big advantage to the DS18B20 is that it's directly supported by the Picaxe firmware. The LM95172 would present interface problems as it is unlikely to use the OneWire protocol used by readtemp. If it was effecively a drop in replacement at the right price It might be attractive.
I can find no regular local supplier here in the UK and the best price I seem to be able to come up with is around 27 USD.
http://www.findchips.com/avail/?part=LM95172&partner=DS4U&utm_source=DS4U&utm_medium=Link
Your go . . .
I remain to be convinced about the code to handle this device, suitable suppliers (anywhere) and a reasonable price.Honest, I'm only an advocate and not the Devil . . .
Difficult to tell at times though!westaust55
Moderator
Have just looked at this thread.
In summary, 57 bearings to monitor and max temp around 100 degC and distances to 420 feet / 73 metres.
As already mentioned the DS18B20 is rated up to 125 degC.
Noting also other commentary about higher bearing temps but from my experience with monitoring of bearing for larger motors and associated gear boxes, the warnings are often set around 90 degC and the trips set about 10 degC higher.
If the above is all correct and valid, then an option is to use 1-Wire networks.
This requires and X1 and X2 chip with 1-Wire commands which allow many DS18B20’s to be connected to a single PICAXE input pin (pin MUST be capable of both input and output).
You could in fact have all 57 temp sensors on one PICAXE IO pin as a single 1-Wire network but you can also consider using say 1 entire PICAXE port of 8 IO pins, with 7 or 8 temp sensors per IO pin.
I have posted details about my past research and work/experiments with 1-Wire networks here:
http://www.picaxeforum.co.uk/showthread.php?15306-One-Wire-Devices-Networks
I have had around 25 1-Wire devices of assorted types connected to a single network.
In summary, 57 bearings to monitor and max temp around 100 degC and distances to 420 feet / 73 metres.
As already mentioned the DS18B20 is rated up to 125 degC.
Noting also other commentary about higher bearing temps but from my experience with monitoring of bearing for larger motors and associated gear boxes, the warnings are often set around 90 degC and the trips set about 10 degC higher.
If the above is all correct and valid, then an option is to use 1-Wire networks.
This requires and X1 and X2 chip with 1-Wire commands which allow many DS18B20’s to be connected to a single PICAXE input pin (pin MUST be capable of both input and output).
You could in fact have all 57 temp sensors on one PICAXE IO pin as a single 1-Wire network but you can also consider using say 1 entire PICAXE port of 8 IO pins, with 7 or 8 temp sensors per IO pin.
I have posted details about my past research and work/experiments with 1-Wire networks here:
http://www.picaxeforum.co.uk/showthread.php?15306-One-Wire-Devices-Networks
I have had around 25 1-Wire devices of assorted types connected to a single network.
Probably correct.
No problems.I first came across RS485 whilst employed as a Marine Electronics Engineer. In this field, NMEA rules supreme, with the RS422 opto-isolated interfaces.
Later I came across this device Because it included RS485, and I didn't know anything about it, I read up on it.
For a comparison table read this link.
I agree with WA55 that the 1-wire system has a lot of promise. My only gripe with it is that when using 57 temperature sensors, you need a look up table of all serial numbers and a way of mapping them all so that you know which bearing has issues. ie each s/n needs a readable naming convention.
Just my 2c worth.
MPep
A random thought for the pool. Why not have an 08M2 with temp sensor(s) for each bearing? These remote 08M2s could be polled from a master picaxe, using a validation text, to make things user friendly - IE . Sheilded stranded CAT6 cable is easily come by. With a project of this size the cable investment & labour to install will dwarf the cost of a few extra 08M2 chips. Also things need to be kept as simple as possible - so the next soul can fix it if/when it breaks.
Code:
SerTxD ("Noel Temp-RF Trial1.bas, Jan 2012")
' DS18S20 on C.1
' 4k7 Pullup on C.1
' RF Tx on C4 direct
' RF power from C.2
START:
SYMBOL BUS = Pinc.1
SYMBOL BusPin = C.1
SYMBOL TXD = C.4
SYMBOL PWR = C.2
SYMBOL BAUD =T4800_8
setfreq M8
pause 1000
SCANBUS:
IF BUS = 0 then
DO
IF BUS =1 then LISTEN
LOOP
ENDIF
goto SCANBUS
LISTEN:
Serin [5,SCANBUS],BusPin,BAUD,("Port-3"),b1
IF b1 <> 1 then TEMP 'Command not for task 1
TEMP:
high PWR 'switch DS sensor on
nap 6 'wait 1 second
readtemp c.1,b0
serout TXD,BAUD,(85,85,85,85,"Port-3",b0) 'send data (TX)
low PWR 'switch DS sensor off
goto SCANBUSwestaust55
Moderator
CAT6 cable comprises 4 twisted pairs without a screen.
Adding a screen to such data cables increases capacitance and in effect reduces distance and/or transmission quality.
The code given with SEROUT having 85's as a form of preamble is more suited to a wireless link. A preamble of this type is not required for cabled (eg CAT6) based comms.
Adding a screen to such data cables increases capacitance and in effect reduces distance and/or transmission quality.
The code given with SEROUT having 85's as a form of preamble is more suited to a wireless link. A preamble of this type is not required for cabled (eg CAT6) based comms.
This script was adapted form one I used for just that purpose - a wireless tempreture monitor - didn't remove the 85s..
Cat 6 can be screened. S
ee Farnell's page on http://cpc.farnell.com/1/1/64061-category-6-shielded-cable-305m-pp7092-pro-power.html
Specifications here http://cpc.farnell.com/jsp/level5/module.jsp?moduleId=cpc/472971.xml
When running shielded data its imperative to grounfd the shield at only one end, leaving the far end unconnected.
@ Dave: I have pondered the effect of terminating the far end into 100R resistors.... What are your thoughts on this with erespect to noise supression and terminating into a ballanced impedance? I will get around to trying this in a noisey (electrical) environmenr one day..
Cat 6 can be screened. S
ee Farnell's page on http://cpc.farnell.com/1/1/64061-category-6-shielded-cable-305m-pp7092-pro-power.html
Specifications here http://cpc.farnell.com/jsp/level5/module.jsp?moduleId=cpc/472971.xml
When running shielded data its imperative to grounfd the shield at only one end, leaving the far end unconnected.
@ Dave: I have pondered the effect of terminating the far end into 100R resistors.... What are your thoughts on this with erespect to noise supression and terminating into a ballanced impedance? I will get around to trying this in a noisey (electrical) environmenr one day..