Espritmodel.com Telemetry Radio
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Old May 30, 2010, 06:16 PM
PLD
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John,

I guess for me the higher bits etc are in that race to the bottom of the abyss. It would be rather 'amazing' to see 0.025mR resolution but you're right, realistically it isn't really needed, not practical to use in standard environments.

Time for me to get to work on the firmware again - though I actually need to build myself another LOM now - since you've got the first build.

Paul.
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Old May 25, 2011, 06:03 AM
PLD
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Breathing some life back into this thread.

I've created a new revision of the board, new layout and new external design.

The gains are a lower noise floor and even better resolution along with a serial connection and calibration option for those needing such certification.

The display will be upgraded to a 16x2 LCD and I'll be adding more information such as min/max values to the output.

Paul
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Old May 25, 2011, 06:23 AM
ancora imparo
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So can I buy SN:0002?

I actually use this gadget more than I thought I would. (And I would love to not have the garbage at start up )

J
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Old May 25, 2011, 06:32 AM
PLD
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Oh my, how dreadfully embarassing - sorry about that. Time slips away and promises fade

You can get SN:0003
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Old May 25, 2011, 06:34 AM
ancora imparo
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'S OK Paul. I already have some nice Kelvin connectors to suit. Providing you don't change the bloody connectors that is.

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Oh my, how dreadfully embarassing - sorry about that. Time slips away and promises fade

You can get SN:0003
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Old May 29, 2011, 10:31 PM
PLD
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I did have on the new board a 11~14 turn trimmer to pull the reference resistor to 10.000R, but I've since decided that instead, I'll make it that the true value of the resistor can be programmed in via the serial port or perhaps the front-panel.
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Old May 29, 2011, 11:50 PM
ancora imparo
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So Paul, are you making this user calibration through the serial port and some PC utility or is it just ISP and you need an ISP programming board?

If the latter, front panel would be good for people who aren't into micros (like me). Could also double as a zero/tare function to null out any residual resistance before measuring?

J
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I did have on the new board a 11~14 turn trimmer to pull the reference resistor to 10.000R, but I've since decided that instead, I'll make it that the true value of the resistor can be programmed in via the serial port or perhaps the front-panel.
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Old May 29, 2011, 11:56 PM
PLD
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Essentially the true value of the reference will be stored in the EEPROM, so there's 3 options as covered; ISP header, serial port (requires support firmware to handle it), or front panel (would make it that something internally has to be shorted or set to force it into calibrate mode). The front-panel option could be as simple as just the 1 button and pressing/holding-it-down makes the system cycle through the acceptable range (eg, 0.1% of 10 ohms, probably 9.9900 -> 10.0100, it's 200 steps but given that you'd only calibrate once a year or maybe 6 months it's not a major chore).

Paul.
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Old May 30, 2011, 12:06 AM
ancora imparo
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Just thinking aloud without knowing anything about the limits of the micro/memory but could you program fairly simply:

1) PRESS to enter "hold mode" to store the min value of R (the real number once it settles down) in normal use. The AEO-RC wattmeter works this way and it's dead simple to understand and very useful. Press again to go back to real time display.
2) HOLD for 3 secs to enter calibration then press or hold to change the value. Turn off to store it.

John

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pressing/holding-it-down makes the system cycle through the acceptable range (eg, 0.1% of 10 ohms, probably 9.9900 -> 10.0100, it's 200 steps but given that you'd only calibrate once a year or maybe 6 months it's not a major chore).

Paul.
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Old May 30, 2011, 01:00 AM
PLD
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I'll be going with a 16x2 LCD display on this one - so I'll actually have min/max/avg display concurrently.
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Old May 30, 2011, 01:04 AM
ancora imparo
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Even better!

Think the press for 3 secs to enter calibration is simpler than an extra switch/link somewhere on the board. Should be cheaper too? You could put the pushbutton inside the case which means it is only accessed when you really need to, avoids any mistaken calibration by folks who don't need to do so, and means one less thing to fit in the case.

J
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I'll be going with a 16x2 LCD display on this one - so I'll actually have min/max/avg display concurrently.
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Old Sep 11, 2011, 02:19 AM
PLD
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FINALLY... here we go... what you've been waiting for...

Need to bench run it for a couple of days, make sure it's all good - then it's shipping time

btw, this is technically #0004, though it's the first shipped one.
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Old Nov 03, 2011, 07:45 PM
KJ4WFG
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'Lo Paul -- I'm just starting to catch up on your threads and came across this one on the LOM. Obviously I could use it to QC my solder joints, which I'm always worried about. I recently smoked a 10 amp H.K. ESC when I hooked it up to a 24g. BL motor that had been running fine when I took it out of service. So now I don't know if I have a bad motor or whether I got in a bad ESC. I have a few diagnostic tools, but not a current limiting source of power to use when I bring a new power system on line. Would the LOM let me compare the 3windings of a BL motor to eliminate the motor as the root cause of the smoked ESC? Then lastly, I think I need to be able to track the internal resistance in my LiPo's as they age and experience life's issues, but I don't really know how to do that, and more especially to do it accurately. Would the LOM have a role there? Regards.............R
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Old Nov 03, 2011, 08:11 PM
PLD
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modbuilder,

The LOM won't help with tracking the IR of the lipo packs, for that you need an IRM (Internal resistance meter). I do have an IRM but it's a 2-wire unit only which means it's difficult to eliminate the wire resistance in the test. I have a 4-wire unit planned but it keeps trying to turn into a mammoth project handling 6S packs with 2kW load ratings.

The LOM7 is for looking at passive resistance, connectors, wires/looms, circuit-tracks etc. It will let you find shorted or imbalanced windings too.

Paul.
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Old Nov 16, 2011, 01:48 AM
PLD
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Update

New LOM power boards have arrived, though still waiting on the new main-boards with the extended reference resistor options.

Need also the right current-limiting resistors for the power boards to arrive.

Paul.
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