Author Topic: finding short on motherboards with a shorty (with display)  (Read 54107 times)

Miti and 2 Guests are viewing this topic.

Offline CaptainBucko

  • Contributor
  • Posts: 17
  • Country: au
Re: finding short on motherboards with a shorty (with display)
« Reply #175 on: May 20, 2024, 05:44:29 am »
After a certain period of operation of the device Shorty Pen (frequent calibrations), malfunctions began.

What FW version? v1.02.03 was released a month ago on the GitLab site.

plus a few photos from the top side load of components from yesterday. Last time I hand soldered 0603 was 15 years ago, and I remember using too much solder. back then. Oh well, bigger the blob, better the job.....


« Last Edit: May 20, 2024, 09:12:35 am by CaptainBucko »
 

Offline Pater

  • Newbie
  • Posts: 1
  • Country: cz
    • paterweb
Re: finding short on motherboards with a shorty (with display)
« Reply #176 on: June 01, 2024, 07:00:57 pm »
I also assembled short -circuit finder. Thank you for publishing the documentation. I allowed myself to add a current source to the connection.

The code has been redesigned. The measurement is accurate enough. My solution can be found here (only Czech, the translator will do a good job).
 
The following users thanked this post: kripton2035

Offline Evi

  • Regular Contributor
  • *
  • Posts: 105
  • Country: ru
Re: finding short on motherboards with a shorty (with display)
« Reply #177 on: June 02, 2024, 12:45:53 pm »
My variant.
1. No current when no measurement - battery longer life. Lower measurement current due to absence of 2 Ohm resistor.
2. Simplyfied calculation: Rx = (volts / 27) / (current); More accuracy.
3. My SW stored and displays last measured Rx minimal value between measurements instead of -----. It is more convenuent.
4. Current measured on 1 Ohm resistor during calibration and stored in EEPROM.
« Last Edit: June 02, 2024, 12:58:11 pm by Evi »
 
The following users thanked this post: indman, Pater

Offline indman

  • Super Contributor
  • ***
  • Posts: 1029
  • Country: by
Re: finding short on motherboards with a shorty (with display)
« Reply #178 on: June 02, 2024, 01:53:15 pm »
Evi,thanks! Can I have the Proteus project and the firmware?
 

Offline Evi

  • Regular Contributor
  • *
  • Posts: 105
  • Country: ru
Re: finding short on motherboards with a shorty (with display)
« Reply #179 on: June 02, 2024, 02:19:23 pm »
Sure!
Anybody can.


Fast and dirty
« Last Edit: June 02, 2024, 02:31:54 pm by Evi »
 
The following users thanked this post: indman

Online mawyatt

  • Super Contributor
  • ***
  • Posts: 3435
  • Country: us
Re: finding short on motherboards with a shorty (with display)
« Reply #180 on: June 02, 2024, 02:29:39 pm »
My variant.
1. No current when no measurement - battery longer life. Lower measurement current due to absence of 2 Ohm resistor.
2. Simplyfied calculation: Rx = (volts / 27) / (current); More accuracy.
3. My SW stored and displays last measured Rx minimal value between measurements instead of -----. It is more convenuent.
4. Current measured on 1 Ohm resistor during calibration and stored in EEPROM.

Nice work!! Not a criticism just a comment, might consider added another protection diode in reverse on the op-amp input to protect for negative input voltages. The circuit shouldn't generate negative voltages wrt ground, however a circuit under test could have a residual negative voltage wrt to ground. Also might consider moving the protection diodes on the other side of the 1K resistors, or even better add an additional pair of back to back diodes across the force terminals, which should provide a high degree of instrument protection against rogue DUT voltages. Some folks have reported damaging LCR meters with large capacitors that have a residual charge, so these kinds of things do happen :o

Anyway, all these are clever circuit implementations :-+

Best,
« Last Edit: June 02, 2024, 02:37:47 pm by mawyatt »
Curiosity killed the cat, also depleted my wallet!
~Wyatt Labs by Mike~
 

Offline Evi

  • Regular Contributor
  • *
  • Posts: 105
  • Country: ru
Re: finding short on motherboards with a shorty (with display)
« Reply #181 on: June 02, 2024, 02:33:03 pm »
Of course.

 

Offline CaptainBucko

  • Contributor
  • Posts: 17
  • Country: au
Re: finding short on motherboards with a shorty (with display)
« Reply #182 on: June 19, 2024, 01:09:39 pm »
My Shorty is up and running (mostly) - I made a mistake during component substitution for U1, selecting a 1.2v instead of 1.85v. That's on order, but has delayed the final fitting and calibration. Corrected BOMS are attached.

I also blew up the first STM32 Micro as a result of a dumb ground loop issue that caused 15vAC on the tip of my soldering iron. The STM32 drew 60mA instead of 3mA on power up! That took a while to track down the fault and root cause.

Also, my cheap Chinese ST-Link v2 clone had the plastic embossed triangle (indicating Pin 1) on the 2x5 PIN header in the wrong location with respect to the actual pin wiring. That also cost me a bit of time.

Once these issues were straitened out, programming was strait forward using STM32-Cube-Programmer. While putting in an order the 1.85v LDO above from Mouser, I decided to add some STM32 Dev Boards to get to free shipping. Reading more on this device, I think it will replace my aging ATMEGA platforms.


 

Offline Evi

  • Regular Contributor
  • *
  • Posts: 105
  • Country: ru
Re: finding short on motherboards with a shorty (with display)
« Reply #183 on: June 19, 2024, 01:37:13 pm »
I found it usefull to make it as plug-in module for M5STICKC.
« Last Edit: June 19, 2024, 03:15:01 pm by Evi »
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf