This thread has been locked.
If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
Part Number: EK-TM4C123GXL
The non-profit I work for (Smoky Mountain Scientific, smokymtsci.com) develops and sells low cost, open source instruments for science education. One of our instruments incorporates a Tiva-C launchpad that outputs a pwm voltage and measures voltage and current passed in electrochemical reactions. I recently purchased 100 Tiva launchpads from Mouser and I am having trouble with noise in the analog read channels for about 1/4th of the boards. We have been building and selling these instruments for a couple of years now and have never had this problem before. To test the boards, I send a pwm signal through a simple low pass filter (a resistor and a capacitor) then read the output on two channels (A11 and A8). The attached figures show examples of output from a good (file Board46) and a bad (file Board37) boards as displayed on our user interface. I put the apparatus together on a grounding mat and then plug the usb connector into my computer to flash the microcontroller and do the testing. I have posted a description of this on the 43oh web site (forum.43oh.com/.../ and have contacted Mouser about it. Mouser said that I needed to bring the problem to the e2e forum before they could do anything. Any recommendations?Thanks,
In reply to Jack Summers11:
Jack Summers11...test protocol involves attaching a test resistor across the electrode leads
Might the method of such, "Attaching a test resistor across electrode leads" in itself - cause or contribute to your issue? Is the attachment's connection: secure, guaranteed to be low inductance & resistance, oxidation/contaminant-free and repeatable over time (and between set-ups.) (note: the build-up of oxidation upon such "connections" predictably introduces "random and unwanted measurement variation.") My firm frequently visits firms where, "insufficient time" has "justified" less than: "pristine, robust, and stylized inter-connects" - which too often gives rise to conditions - (just) as you report.
Beyond this - the presence of new/added cells, tablets, IOT devices - operated or connecting at random times - all w/the potential to "add noise." (unaddressed - to this point...)
As always - your analog front end must strive to best match the input impedance of the MCU's ADC - and in your case - may benefit from (even) shorter connections - and those routed via, "shielded" cable.
It is expected that your use of: "Additional & Over-Cautions" may best enable systematic, "Caution Reduction" - which best identifies the point(s) of maximum system weakness/noise admittance...
We are glad that we were able to resolve this issue, and will now proceed to close this thread.
If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.
In reply to Robert Adsett72:
Re: Caps DO Fail... (I could not import your "quote"...)
Exactly my (previous) point - rejected by our poster - yet "just as you report" - firm/I have "changed Cap values thru "breathing" and have witnessed their "falling apart" (when ever so gently probed) and when "excitement is required" - we've seen electrolytics LAUNCH - and embed themselves in our (once) pristine dropped ceiling... Wishful thinking (all is well) may not always prove, "Accurate Thinking..."
In reply to cb1_mobile:
In reply to Dubnet:
Make that, chuckle ++; Candidate for, "Best TAG ever!"
And ... interestingly noted ... such "Light Emitting (i.e. likely Smoking) Capacitor" flows from the ... (drumbeat maestro)... ... Smoky Mountain! (no one could, "Make this stuff up!")
(2nd place awarded: via (gentle) admonition to poster - via Robert's, "Every Tag known to man" - as you've just supplied - "may prove (bit) much!")
 Can it (really) be considered, "Indian Giving" when (yet another) TAG vies for 2nd Place? May I nominate, "Light Emitting Capacitor - Doesn't even Work!" (accompanied w/ongoing "whine & tear-stains AND - at minimum - three such failed (yet different) caps...?")
note: "Indian Giving" is an idiom which describes (some) initial award - and (later) the award's withdrawal... (often - w/out justification...)
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.