Failure Analysis - Not thinking through connector locations

Failure happens from time to time when building projects or creating things.  I'm lucky that most of my mistakes are fixable after the fact or that the cost is negligible.

I have a 10 year old project I wanted to update.  It is a stack of three boards.

  1. The bottom board is an Arduino Ethernet
  2. The middle board is a spacer that raises the third board above the ethernet connector.  The middle board has been cut to avoid touching the Ethernet connector
  3. The top board a NeoPixel 8x5 LED array
I wanted to add a Nokia 5110 LCD to the board to show status and configuration.

This Arduino Ethernet board has some stuff going on.  The left side of the board looks like it is the side that we would expose through a bulkhead panel.  The right-hand side has a programmer connector. I made that a 90-degree right-angle connector so that I could plugin in a serial-to-USB adapter while a shield was stacked on top.

The thing is to remember that the left-hand side is going to be mounted so that it is reachable from outside the case.


I added a prototyping shield to the top of the Arduino Ethernet board.  I cut a notch in the prototyping board where the big Ethernet connector is so that the board could lay flat on top of the Arduino. I didn't want to lose any stacked connectors because we have a 3rd layer coming.  But it looks the upper left corner probably could have been neater.  The little fragment labeled "reset" was probably retained for a button but I doubt it works the way it was cut.

This was the first minor fail.


I added a header for an LCD display in the bottom left.  There is a NeoPixel panel going on top of this protoboard.  That means the pins can't stand upright.  I mounted them on the left, next to the edge. The thing works great. 

Then I realized that the LCD pins stick out too far past the other connectors.  They are in the wrong spot for a cable connection. 

They really aren't in the right spot to solder the LCD board directly to them.  I had intended to mount the LCD on a different edge and now we'd be locked into mounting the LCD at that location.  

Hacking it Up

We could remove the connector or leave the connector but remove the jumper wires and start over with a new connector.  I didn't want to do any of that because I was afraid of destroying a pin. Some days my soldering skills aren't great.  I could have cut the connector off and then pulled the pins 1 by 1.

The final decision was to
Bend the connector 180 degees  so it would be facing the other way.

You can see in the picture that the cable now runs the length of the protoboard.  This means the LCD can be used anywhere without impacting the physical design.

Thoughts

This could have gone badly. The connector pins could have broken.  The solder connections could have ripped the connector pins out of the board. I've had plenty rendered unusable after this type of fix.

Comments

Post a Comment

Popular posts from this blog

Installing the RNDIS driver on Windows 11 to use USB Raspberry Pi as network attached

Image
I do a lot of my development and configuration via ssh into my Raspberry Pi Zero over the RNDIS connection. Some models of the Raspberry PIs can be configured with  gadget drivers  that let the Raspberry pi emulate different devices when plugged into computers via USB. My favorite gadget  is the network profile that makes a Raspberry Pi look like an RNDIS-attached network device.  All types of network services travel over an RNDIS device without knowing it is a USB hardware connection. A Raspberry Pi shows up as a Remote NDIS (RNDIS) device when you plug the Pi into a PC or Mac via a USB cable. The gadget  in the Windows Device Manager picture shows this RNDIS Gadget connectivity between a Windows machine and a Raspberry Pi. The Problem Windows 11 and Windows 10 no longer auto-installs the RNDIS driver that makes magic happen. Windows recognizes that the Raspberry Pi is some type of generic USB COM device. Manually running W indows Update  or  Update Driver  does  not  install the RNDI
Read more

Understanding your WSL2 RAM and swap - Changing the default 50%-25%

Image
The Windows Subsystem for Linux operates as a virtual machine that can dynamically grow the amount of RAM to a maximum set at startup time.  Microsoft sets a default maximum RAM available to 50% of the physical memory and a swap-space that is 1/4 of the maximum WSL RAM.  You can scale those numbers up or down to allocate more or less RAM to the Linux instance. The first drawing shows the default WSL memory and swap space sizing. The images below show a developer machine that is running a dev environment in WSL2 and Docker Desktop.  Docker Desktop has two of its own WSL modules that need to be accounted for.  You can see that the memory would actually be oversubscribed, 3 x 50% if every VM used its maximum memory.  The actual amount of memory used is significantly smaller allowing every piece to fit. Click to Enlarge The second drawing shows the memory allocation on my 64GB laptop. WSL Linux defaults to a maximum RAM size of 5
Read more

Almost PaaS Document Parsing with Tika and AWS Elastic Beanstalk

Image
The Apache Tika project provides a  library capable of parsing and extracting data and meta data from over 1000 file types.  Tika is available as a single jar file that can be included inside applications or as a deployable jar file that runs Tika as a standalone service. This blog describes deploying the Tika jar as an auto-scale service in Amazon AWS Elastic Beanstalk.  I selected Elastic Beanstalk because it supports jar based deployments without any real Infrastructure configuration. Elastic Beanstalk auto-scale should take care of scaling up and down for for the number of requests you get. Tika parses documents and extracts their text completely in memory. Tika was deployed for this blog using EC2 t2.micro instances available in the AWS free tier. t2.micro VMs are 1GB which means that you are restricted in document complexity and size. You would size your instances appropriately for your largest documents.   Preconditions An AWS account. AWS access id and secret key.
Read more