Eagle tree elogger V3 - Cheap DIY Thermistor? Found+Tested!

[ZapPat]

*EDIT* - Scroll down a few posts to see what thermistors you can get cheap that will work!

Does anyone know what thermistor is compatible with eagle tree's elogger V3? I know it's a 10k NTC type, but have no idea of the "B values" that describe the sensor's response slope or resistance vs temperature.

I am waiting on an answer from eagle tree themselves, but I am not sure if they will actually want to tell me this info, since they might prefer to sell me their pre-assembled dongle instead. I must say their customer service is quite slow, and I don't want to wait any more.

If no one knows, I will proceed with doing some testing using a 10k pot and an offset resistor, and find out myself what thermistor is needed.

Thanks!

 

[fechter]

You could just get one and test it against a calibrated thermometer.
These are cheap: http://www.mouser.com/Search/ProductDetail.aspx?qs=pS/9HF6wRJQlp6njAF1eTA==

 

[ZapPat]

After some testing using a potentiometer and the data logger itself, I've managed to select a couple parts that will probably work from digikey. Here's what I found out about the B values using some math and my test results:

B25/100 = ~3966
B25/85 = ~4011
B0/50 = ~4406
B25/50 = ~1794

I've ordered the following parts from digikey to try out, the most promissing (and cheapest - 0.48$) being the epcos chip thermistors listed first:
495-2116-1-ND
BC2299-ND
495-2153-ND

If anyone is interested, I'll post the results of which one(s) works best for this DIY thermistor solution for the eagle tree datalogger v3.

The logger can take up to three temperature probes at once, so I'm planing on one in my hub motor, one in the battery, and another on the controller. Talk about being data-hungry, maybe I'm just a bit crazy! Anyways, at 50 cents each instead of 10$ from eagle-tree, I'll be hard-wiring these sensors into many different projects so I can just move the logger itself from one place to another without having to move the sensors.

 

[silicium]

For the Data logger POWER ANALYSER PRO (Medusa Research) It's too a NTC 10kohms for the temp sensor...

 

[RLT]

A
495-2153-ND
If anyone is interested, I'll post the results of which one(s) works best for this DIY thermistor solution for the eagle tree datalogger v3.

YES! Please!

 

[ZapPat]

In search of cheap, compatible thermistors for the eagle tree elogger v3 data logger, I did a wee bit of reverse engineering and found some possible replacements to eagle tree's 10$ offerings;

I've ordered the following parts from digikey to try out, the most promissing (and cheapest - 0.48$) being the epcos chip thermistors listed first:
495-2116-1-ND
BC2299-ND
495-2153-ND

Well, I've now quickly tested all three thermistors at once on the elogger, and used a fairly cheap Rat Shack electronic thermometer to compare the results to. I will test them better some other time using a setup that will garantee me uniform temperatures for every sensor (like using liquid, or mounted on a thick heat spreader or something similar). Anyways, here are the best two of the three I've tested:

1 - Epcos B57421V2103J62, Digikey part # 495-2116-1-ND, about 0.45$ (in tens), surface mount chip (need small iron + dexterity to use these)
2 - Epcos B57871S0103F001, Digikey part # 495-2153-ND, about 2.50$ (in units), bead type case

When I do a more presice test with all three sensors, I'll post the elogger produced graph here.

Also, I have one request for any savvy RC guys reading this: Please post links to this thread on any RC forums you like, because from what I've seen, this is first time [unique] information about this DIY solution on the web, and it is mainly RC-oriented product. And I am not a hard-core RC guy, so don't post there.

PS: You may wonder why I insist on spreading this info? Mostly because an eagle tree support person was supposed to get back to me about this info, but has not responded at all. So piss on them for being such information mongers! (And having generaly slack customer service I must add - A pitty, because it's an interesting product, and is an alternative to the CA or Watts Up meters for ebikes, when the LCD add-on is used with it.)

Enjoy!

 

[RLT]

Cool,

Thank you.

 

[nasukaren]

So any updates on this thread?

I'd also like to needle EagleTree a bit more into making their product open source and expandable. They really need to open up the data tx protocol -- as well as let us know what the sensor values are so we can hack them ourselves.

K

 

[ZapPat]

So any updates on this thread?

I'd also like to needle EagleTree a bit more into making their product open source and expandable. They really need to open up the data tx protocol -- as well as let us know what the sensor values are so we can hack them ourselves.

K

The two thermistors I listed above seem to work well, but I have not taken the time to test them against a precise temperature sensor yet - I don't even have an "official" sensor from eagle tree to test against. However I am quite confident that they are using thermistors with specs very similar to the ones I found, as there are not very many that fit the bill according to my calculations.

I actually mostly use my own data logger these days as a display device for my ebike, and I'm not even currently using a temperature sensor on it! I'll add one soon though for my LiPo pack on my next 2WD hub motor beast, since I might actually start pushing the cells towards their limits this time so they might make some heat to be measured...