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HelicopterRadio - JR DMSS › JR Temperature Telemetry Sensor
06-07-2014 01:24 AM  3 years agoPost 1
mpafonseca

rrApprentice

Savannah, GA - USA

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Hello All,

I have a JR TLS2-TMP temperature sensor installed in my T-Rex 600N on the engine side of the muffler bolt. I know that it is not the ideal place to measure the temperature but I "calibrated" it since it is usually about 10deg C lower than the head.
It works ok but the issue is that it keeps breaking the sensor due to the normal engine vibrations. I tried to put some silicone RTV to help, hold the wire in more places, etc. but it keeps happening. I'm like to have it to monitor the engine but I'm tired to buy 30+ bucks sensors... So Does anybody know what is the p/n of the temperature sensor component so I can replace it only? I can do some calibrations if needed with an external temp gun, but as long as it measure something it will be ok for me...

Here are the pictures of the sensor. It usually breaks the "wire" at the sensor base.

Thank you!!

Marco

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06-07-2014 04:11 AM  3 years agoPost 2
JEEPWORLD2002/2

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Blue Bell, Pa

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My guess is wires were to taught ?? I would think that's not the best design well for nitro that I usually they use a loop wire type sensor for nitro/gas that looks more for a ep setup

If you were to use that type sensor again I would get a small piece if aluminum drill a hole snip off the bolt eyelet n insert the wire end of that sensor into the hole n fill the hole with thermal compound then mount that to the motor. I was thinking a piece of aluminum dowel rod say 1/4" drill two hole to mount it n the hole say 1/16" in the center of the rod

Usually these type of thermal couples are typed f x x you could find the type n order a new thermocouple from digikey. Com

Trex600n,Trex500,MR25,MikadoLoGo5003d/KDE,Goblin 380XNova,CastleCreations,Ys,JR XG8,Tags Mini XBus Dmss//FAA# FA3NYC9TAP

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06-07-2014 03:13 PM  3 years agoPost 3
mpafonseca

rrApprentice

Savannah, GA - USA

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Thank you for your reply. I also think that the design is not optimal. I know that there are better thermistor configurations in the market I just don't know the specs for the JR circuit to keep it calibrated. The use of the axial thermistor that imposes a 180degree bend in the wire is causing the weak spot. If I knew the thermistor spec I would be able to replace it by one with both wires on the same side that I believe would handle the vibrations better. I will try to measure the calibration of the radio inputs to back engineer the thermistor spec. Lets see if it is going to work...

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06-07-2014 04:07 PM  3 years agoPost 4
Four Stroker

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Atlanta

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I have been using that very sensor for 4 months without any problems. I did ask if the sensor only was available because I predicted this kind of thing.

I don't know why yours is breaking because I have not seen it installed. But I would suggest not bending the wire too much at the sensor and mounting the wire shortly after the sensor to the frame so that the entire wire does not flop around.

I should be possible to measure the sensor - ice water and boiling water - and find one of similar specs. However, it may be calibrated after it is assembled.

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06-07-2014 08:16 PM  3 years agoPost 5
jesse

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Houston, TX.

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I too have been using on my gas planes which have way more vibration I would really make sure your not bending the terminal and not to pull it tight. as far as the sensor it self I wish I could help but have no idea what sensor they use.

Agile Sky-hero team Team jramericas.com Field Rep Spin Blades

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06-07-2014 11:27 PM  3 years agoPost 6
JEEPWORLD2002/2

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Blue Bell, Pa

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Think it all depends on the resistance of the thermocouple ??

Trex600n,Trex500,MR25,MikadoLoGo5003d/KDE,Goblin 380XNova,CastleCreations,Ys,JR XG8,Tags Mini XBus Dmss//FAA# FA3NYC9TAP

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06-08-2014 01:58 AM  3 years agoPost 7
mpafonseca

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Savannah, GA - USA

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I did some research with my broken sensor and so far this is the calibration curve I was able to plot using my "free" Harbor Freight Multimeter.

If anybody knows a good source of thermistor specs I believe we can find a replacement with better mechanical characteristics.

I believe the one JR uses is this one...

http://www.exsense.net/en/ProductShow.asp?id=21

I think it is going to work!!

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06-08-2014 07:30 AM  3 years agoPost 8
JEEPWORLD2002/2

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Blue Bell, Pa

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Here u go digital key dot com

I did search for thermocouples but it may be listed as a thermistor but I sure they will have it

http://www.digikey.com/product-sear...?k=Thermocouple

Trex600n,Trex500,MR25,MikadoLoGo5003d/KDE,Goblin 380XNova,CastleCreations,Ys,JR XG8,Tags Mini XBus Dmss//FAA# FA3NYC9TAP

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06-09-2014 02:14 PM  3 years agoPost 9
mpafonseca

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Savannah, GA - USA

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I ploted the data in a Log scale and calculed the thermistor characteristic equation. The measurements I made gave me the following:

R@25deg.C = 200k
B =~3900k

I looked all thermistors at digikey and mouser.com but the closest one is a Honeywell that has a very bad tolerance value of 20% (and a B =4200). This will give me some deviations on the expected measurements but... If anybody knows other sources for thermistor (small quantity) orders please let me know.

In the mean time I ordered some Honeywell sensors to test.

The good side is that they are cheap

Thank you,

Marco

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06-10-2014 04:08 PM  3 years agoPost 10
JEEPWORLD2002/2

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Blue Bell, Pa

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try these guys

http://www.omega.com/temperature/tsc.html

Trex600n,Trex500,MR25,MikadoLoGo5003d/KDE,Goblin 380XNova,CastleCreations,Ys,JR XG8,Tags Mini XBus Dmss//FAA# FA3NYC9TAP

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06-11-2014 12:40 AM  3 years agoPost 11
mpafonseca

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Savannah, GA - USA

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Thank you for the link!!

I found the exact match. It is done by ussensor.com p/n 204JG1K.

I sent them an email since no retailer seems to have it in stock. I just hope to find it in small quantities.

Thank you again.

Marco

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06-11-2014 01:44 AM  3 years agoPost 12
JEEPWORLD2002/2

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Blue Bell, Pa

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Cool no problem glad u found it

Trex600n,Trex500,MR25,MikadoLoGo5003d/KDE,Goblin 380XNova,CastleCreations,Ys,JR XG8,Tags Mini XBus Dmss//FAA# FA3NYC9TAP

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06-11-2014 01:21 PM  3 years agoPost 13
Four Stroker

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Atlanta

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Good news. I may need some eventually.

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06-11-2014 02:05 PM  3 years agoPost 14
Ace Dude

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USA

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Would be really nice if you could replace the thermistor with a thermocouple.

  

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06-11-2014 06:57 PM  3 years agoPost 15
Four Stroker

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Atlanta

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Since this is a 10% part, I assume the sensor is calibrated and won't work worth a damn with a replacement thermister. You could get many and try them in your oven. I no longer have access to an oven so would just stick it in boiling water which is close to the head temp. anyway.

So when you get a new sensor, you could pot it with something like M/S 907 and re-shrink wrap. But like the other guy, I have two and have not had any problem with self-destruction.

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06-11-2014 08:32 PM  3 years agoPost 16
mpafonseca

rrApprentice

Savannah, GA - USA

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Four Stroker,
The equations for the thermistors are quite simple to predict and usually the big tolerance is on the resistance at 25degC. The tolerance on the curve slope is between 1 and 2%. So with a single measurement it is possible to "calibrate" the termistor adding a resitor in series. This can guarantee the precision at the temperature range you are interested to measure (in my case between 80 and 120 degC). So I will try to do that. I was not able to find the perfect match one from USSensors because they are not in stock anywhere and the manufacturer sells a minimum of 500. They are cheap since it is 0.50 each but times 500 is a 250 dollars in temperature sensors. If you request so, the manufacturer can provide you the thermistors with 1 or 2% tolerances also.
What I will do is to use a Honeywell sensor that is not exact the same spec, but adding a 2k resistor (to be verified with some calibration runs) to it will make my measurement reasonable until 140degC. I will do it and compare some measurements. My original sensor is already broken so I have nothing to lose except for the 2 bucks worth of sensors

I will let everybody know that I ended up with....

Cheers!
Marco

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06-11-2014 08:44 PM  3 years agoPost 17
Four Stroker

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Atlanta

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OK so the 10% is the resistance tolerance and not the slope ? So if I stick it in boiling water and get 212F (100C), then I am good for at least the range of interest.

What part did you finally get and where did you get it ? Let us know how this works out ! We appreciate (or at least I do) this kind of effort.

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06-14-2014 03:44 AM  3 years agoPost 18
mpafonseca

rrApprentice

Savannah, GA - USA

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Finally I did it!!

I wasn't able to get the "perfect" match thermistor so I bought a Honeywell 135-204QAG-J01 which has the same 200k spec @25degC but a Beta factor of 4200 instead of 3895 I wanted. The tolerance of this thermistor is pretty bad for the value at 25C but since I was going to calibrate it I decided to give it a try.

Comparing the original sensor calibration curve with the Honeywell I got the following curve (original in blue / Honeywell in red).

Then adding about 2k to the basic resistance I approximate the curves to the following.

Which gave me a reasonable accuracy between 80 and 140degC. To do that I added a potentiometer to the assembly...

I really enjoyed doing this due to the amount of things I learned from the JR system, measurement and telemetry. I did some measurements with an external temp. gun and the results were pretty good, specially for the use I have!!

Tomorrow I will test fly it!!

Then, I put all the new assembly on boiling water to check the 100degC value. Since I'm sea level this is pretty accurate. With a little tuning on the trim pot, I got a good reading.

Cheers!!

Marco

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06-16-2014 07:13 PM  3 years agoPost 19
9387ASH

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UK

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How did this work out ?

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06-16-2014 07:23 PM  3 years agoPost 20
mpafonseca

rrApprentice

Savannah, GA - USA

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As I explained above, it worked. Everything is doing ok. The only issue is that I was not able to buy the correct spec thermistor so I had to correct the one I got with a resistance in series. This limited the usable range a little (from 30C to 230C in the original to something close to 80C to 150C). It still reads the full range but the error at the extremes is very high.
I'm still searching for the correct thermistor in small quantities. I wil buy some as soon as I find them.

I need a thermistor that has 200k at 25degC and a Beta equal to 3895k.

Marco

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HelicopterRadio - JR DMSS › JR Temperature Telemetry Sensor
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