kripton2035
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« on: February 14, 2021, 05:50:15 17:50 » |
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Hi everyone, I would like to share a project I made recently : I adapted a shorty device and added a display. it becomes a 0.1mΩ meter with surprising stability. the original shorty project is here : https://hackaday.io/project/3635-shorty-short-circuit-finderI did one showed here ( http://kripton2035.free.fr/Projects/proj-shorty.html) and was pleased with its performances, but it lack a display. so I decided to add one, and here is the result. here is a video showing the measuring of some small values resistors : https://youtu.be/4F6QNSpWToshere another video showing continuous resistance measuring along a soldier roller : https://youtu.be/8mYyr9uKpFUand last another video showing how to find a shorted capacitor on a 820-00165 macbook air motherboard. fast and easy. https://youtu.be/L4V3BWReZLYI'm cleaning the schematic and sources, and will share it when it's ready. I'm building a pcb right now, and will test it before. |
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Checksum8
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« Reply #1 on: February 14, 2021, 07:01:38 19:01 » |
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Nice work!
This project reminds me of a Toneohm 580 which we used many years ago to find shorts in pcb's. It had an inductive sensor, the same company also made a resistance one like your unit.
Could you tell me what frequency and duty cycle the tester is feeding to the PNP transistor?
Thanks for sharing!
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« Last Edit: February 14, 2021, 08:00:17 20:00 by Checksum8 »
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Wizpic
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« Reply #2 on: February 14, 2021, 07:10:14 19:10 » |
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I agree it's a nice project, Seems to work very well like the video's
Looking forward to see the project grow, I will definitely be making one looks like a really useful tool
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« Last Edit: February 14, 2021, 07:13:51 19:13 by Wizpic »
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When you think, "I can't do anymore. I need a break," that is the time to challenge yourself to keep going another five minutes. Those who persevere for even an extra five minutes will win in life..
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kripton2035
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« Reply #3 on: February 14, 2021, 08:48:33 20:48 » |
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Could you tell me what frequency and duty cycle the tester is feeding to the PNP transistor?
it is DC +5v. it is powered at the beginning of the arduino sketch and never powered off. it is a DC milli ohm meter. I suppose it acts as a sort of constant current source. Posted on: February 14, 2021, 07:54:31 19:54 - Automerged
actual state of the pcb I'm building. |
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Wizpic
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« Reply #4 on: February 14, 2021, 09:07:48 21:07 » |
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Looking nice.
What is the current source 100Ma ?
Good to that your using the 4 wire method for the probes
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When you think, "I can't do anymore. I need a break," that is the time to challenge yourself to keep going another five minutes. Those who persevere for even an extra five minutes will win in life..
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kripton2035
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« Reply #5 on: February 14, 2021, 09:21:15 21:21 » |
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around 60mA
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Poty
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« Reply #6 on: February 16, 2021, 05:29:37 17:29 » |
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Excellent work. Just one question and not related to the instrument. Which was the capacitance value of the piece you had to replace on the macbook? Just curiosity.
Regards.
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You can't have your cake and eat it too... except if you do.
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kripton2035
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« Reply #7 on: February 16, 2021, 06:49:53 18:49 » |
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Excellent work. Just one question and not related to the instrument. Which was the capacitance value of the piece you had to replace on the macbook? Just curiosity.
Regards.
all these capacitors that may fail on the 3 banks are 62uF/11V. I've fixed 3 of them by now and it was never the same capacitor. |
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Poty
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« Reply #8 on: February 16, 2021, 08:18:57 20:18 » |
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Did you get it to work? Or (I'm guessing) it starts working and then another cap goes to short and so? Maybe they blow up because another reason... is that the power source stage?
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You can't have your cake and eat it too... except if you do.
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kripton2035
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« Reply #9 on: February 16, 2021, 10:29:29 22:29 » |
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yes the macbook works fine after capacitor replacement. these capacitors are crap they fail after 4-5 years of use.
I did not bother to replace them all, but it would be a good practice in fact.
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Poty
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« Reply #10 on: February 16, 2021, 10:39:38 22:39 » |
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Nice! IŽll wait for your schematics. Seems to be a great tool to build and add to the lab.
Greetings.
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You can't have your cake and eat it too... except if you do.
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kripton2035
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« Reply #11 on: February 17, 2021, 03:11:23 15:11 » |
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Good to that your using the 4 wire method for the probes
it's almost mandatory since you're dealing with milli-ohms, even less. |
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Captain_Boblo
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« Reply #12 on: February 17, 2021, 07:00:23 19:00 » |
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Looking forward to more details and schematics! I built up a couple of "half-ohm" adapters for multimeters, they have been extremely useful for finding shorted traces on home-made PCBs and shorted components. http://jaanus.tech-thing.org/category/half-ohm/I've always wanted a "shorty" but now that you've added a display it is even better! Thank you. |
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Old_but_Alive
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« Reply #13 on: February 18, 2021, 11:17:55 11:17 » |
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@kripton2035
I would be interested in buying a bare pcb from you
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I fought Ohm's Law ... and the law won
I only use Mosfets because I have a Bipolar mental disorder :-)
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mexpcb
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« Reply #15 on: March 03, 2021, 06:42:14 18:42 » |
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very nice project... is this able to use a milliohm range?
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kripton2035
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« Reply #16 on: March 03, 2021, 07:45:17 19:45 » |
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I can read stable result down to 10”Ω and up to 3.5Ω but as there is no precision resistor in the device, you don't have a great accuracy in the displayed value. (but I'm working on it  but you can make relative measurments in the 10”Ω range for a low cost. take a look at this video for the measuring of some low values resistors : https://www.youtube.com/watch?v=4F6QNSpWTos |
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« Last Edit: March 03, 2021, 07:47:38 19:47 by kripton2035 »
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kripton2035
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« Reply #17 on: April 04, 2021, 05:33:17 17:33 » |
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prototype pcb have been ordered. now wait 2 weeks to get them and test them.
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pushycat
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« Reply #18 on: April 05, 2021, 10:28:31 10:28 » |
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Excellent project and a one stop solution for the headache of finding the exact culprit on board. Can you please clarify regarding the probe connections, as the connector shows 5 connections and the red probe picture shows two wires shorted at the soldering point. In addition to the present concept, (Just for a reference) here in this video he uses an additional protection for accidentally frying it with 230v. He uses a Transient Blocking unit (TBU) in series with the probes. His project doesn't display the resistance but simple using an op-amp. https://www.youtube.com/watch?v=N2M-p-OGvPg |
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kripton2035
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« Reply #19 on: April 05, 2021, 11:31:58 11:31 » |
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Can you please clarify regarding the probe connections, as the connector shows 5 connections and the red probe picture shows two wires shorted at the soldering point.
well at some point, the closest possible of the device to test, you must soldier the wires... here I did it at the end of the metal part of the probes, the closest I could do with these probes. so there are 4 wires from the pcb to the probes, and they are soldered at the top end of the probes. |
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pushycat
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« Reply #20 on: April 05, 2021, 02:17:11 14:17 » |
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well at some point, the closest possible of the device to test, you must soldier the wires...
here I did it at the end of the metal part of the probes, the closest I could do with these probes.
so there are 4 wires from the pcb to the probes, and they are soldered at the top end of the probes.
Ok i understood that the 4 wires take an average reading to the measuring tip to calibrate at least resistance at the tip. So can you please shed some light over the centre pin used shown in the schematic which is a ground. I guess it is for the shielding of the 2 probe wires? |
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kripton2035
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« Reply #21 on: April 05, 2021, 02:30:34 14:30 » |
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yes I used an audio shielded cable. left and right goes to the probe, and ground for shielding to the center pin of the din plug.
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kreutz
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« Reply #22 on: June 21, 2021, 03:47:35 15:47 » |
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prototype pcb have been ordered. now wait 2 weeks to get them and test them.
Please, share the results. Regards, kreutz |
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kripton2035
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« Reply #23 on: June 21, 2021, 06:05:09 18:05 » |
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Hi there,
I've got the pcb and tested them.
but I have some spurious oscillation at the output of the opamp
and I'm struggling to find the reason for some times now...
as I have changed some parts of the design, it may come from that, but I have to investigate.
more to come soon, thanks for your patience.
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zelea2
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« Reply #24 on: June 23, 2021, 10:49:52 22:49 » |
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If you don't want to build your own you can already buy such a milliohmmeter with 4 wire probes, Alu case and LiIon battery for 60$ here: https://www.aliexpress.com/item/1005002597400113.html |
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