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Mr.RC-Cam

µMetros: Battery Resistance Meter

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Thanks Mr.RC-Cam ,

I've received the instructions.

The assembly was fairly easy with the silk screen and tracing the schematics.

The only pain was D1 which needed some major heat to solder it properly.

I've still got to get LCD, U2, U3 and U4 .

On my last order from DigiKey I clicked on the wrong delivery method so my shippment is somewhere in the Pacific on a slow boat to Oz :) .

Note to self ... Check twice , click once ....

I'll hopefully have the balance of the parts next week and I'll post again :)

Cheers

Zlatko

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I would like to say mine is going but still waiting for the samples from Dallas, maybe they don't ship to Austraila ?

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If you received a confirmation email from Maxim/Dallas then your samples are on the way.

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Hi All,

Just finished mine.

My kids "borrowed" my plastic screws , so at this stage just held the heatsink with fingers to do the testing. Also have to put it in a box. No issues or problems, worked first go.

Works great :) .

Thank you Mr.RC-Cam !

post-6-1121492550_thumb.jpg

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If you received a confirmation email from Maxim/Dallas then your samples are on the way.

Got the maxi/Dallas IC just waiting fot the Linear IC's did not get a notification for them !

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Zlatko, that is great news. Be sure to shorten the meter leads. If you have heavier leads then that will help too. {I think you would be surprised by the resistance these wires add to the measurement.}

Bthree, that might not be a good sign. I think they should have sent you a notification if the parts were on their way.

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just waiting fot the Linear IC's did not get a notification for them !

Replace the order, I had the same issue and would have waited for years if I had not given it another go ;)

Edited by Kilrah

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Parts arrived... board finished with thanks to RC-CAM

No real dramas.. had to fit in a larger 0.1ohm resistor and used all Linear IC's

post-6-1122795272_thumb.jpg

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Glad to hear it it is working.

I have one PCB/PIC set left. First come, first served. :)

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Bthree,

Your display is bigger than mine ! :)

Nicely done!

I finally "boxed mine" , I havent changed the wires yet, but will use something a bit more "solid" .

I ended up using a different case instead the Serpac one.

I went for the Jaycar one HB-5610 http://www.jaycar.com.au/productView.asp?I...eMax=&SUBCATID=

Slightly longer but thinner compared to the Serpac one and also has a 9V battery compartment. Didn't have to modify the switches, just offset the PCB to the right and everything was great :) , even the power switch was slightly recesed so can't turn it on accidentally.

I had to use metal bolt and nut to retain the heatsink as the smallest plastic ones available here were M3. It seems to work okay.

Thanks again for a great project.

Cheers

Zlatko

post-6-1123039633_thumb.jpg

Edited by Zlatko

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One set left. PM sent.

EDIT: All PC boards are gone -- No more to offer.

Edited by Mr.RC-Cam

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Thanks for the link. That meter is bargain priced. I wonder if it works well.

Adding auto shut off and volts readout to the uMetros would involve a slight redesign of the hardware (it would not be a software only upgrade). If there was more interest in the project I would do that. But, there do not seem to be many folks that want a battery resistance meter. Too bad, since having used it, I have learned how valuable it can be.

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Hi, Mr-Cam

I've just completed the first bench tests for the brand new µMetros ... : :huh:impressive !!!

Congratulations, that's great work.

Few mods were added : Original volt. ref. from Linear, Irfz44 for Mosfet and overall ... µMetros speaks French :wub: !!!

and ... a single side board !!!

I've just a little question: I've seen "Cooling" in the messages ... could you tell me what is happening When it is shown ???

once more : congratulations

Alain

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"Cooling" Messages: There was originally a cooling fan that was controlled by the software. I later found that a fan was not needed. So, the feature was disabled.

These sort of messages will be found when snooping around the hex file.

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:(

Hi, Mr Cam

I've pushed my tests one step further and trapped a beautiful 10 ms every ~ 5 sec pulse on PIC pin 2 ( volt ref drive ) ... instead of a solid "0" level.

:unsure: I had noticed a little current flowing from the battery every 5 sec.

So, I must say this occurs on the steady state, measure button released.

This is not a problem, of course, as the mains and battery do not stay connected to µMetros for a long time , but what is it implemented for ???

Alain

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That intermittent pulse is part of the 9V battery test feature. If the battery that powers uMetros has low voltage then a "Pwr Fail" message appears on the LCD.

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Hi Mr Cam

Did I explain it well ???, the current ( milliAmps ) is flowing from the NiCad battery under test ... not the 9 v Battery.

the .25 mA given by Pic pin2 are not very logical here ...

OK for Power Fail ... which is canceled only when power down ... I renamed it Batt_Low to think :rolleyes: to the 9v Batt.

Alain

Edited by Acetronics

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When it is installed, current flows from the battery being tested at all times (except during the battery test pulse). This was part of the control circuitry for the fan feature that is not used. It also speeds up measurement acquisition.

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:blink:

mmmmh, I just have current flowing from the tested battery when test button pushed ( for ~ 5 sec. if button released as soon ) , and during those 10 ms surprising pulses ...

Most of time, no current flows from the tested battery ... if button not pressed. This is quite normal, as the current sink is disabled ( pic pin2 LOW).

Alain

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My mistake -- you are correct. When I removed the fan cooling feature the constant load current was disabled too. But as mentioned before, the 10mS pulsed current that you see every few seconds is related to the 9V battery test feature. To test the battery, Vref must be turned on (via PIC Pin-2). When Vref is on, the Q1 FET is also turned on for a brief moment. This is not of any real concern at all.

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:D

Ok, I feel better now ...

Thank you for the explanation and once more for this very useful instrument.

Alain

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UPDATE: SOLD!

I have one fully tested uMetros board (naked/uncased) that I built as a spare. I don't need it, so it is available at below my cost to any registered forum member. If interested, please PM me.

Edited by Mr.RC-Cam

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