Minimal Engineering

Today, while on the way home from a weekend at a music festival (my wife as in one of the instrument competitions) , I noticed the camper refrigerator wasn’t working properly.

The refrigerator operates on 12 volts DC, 120 volts AC or propane, and the DC part wasn’t working.

There was an error code being shown on the display, so I looked it up in the manual. The text for that error code was, “Unit not operating correctly”. Wow. That was not terribly helpful.

After checking the two fuses protecting the wiring going to the refrigerator and finding them okay, I searched around on the internet and found some wiring diagrams that included enough information for me to start figuring out the problem.

After about 20 minutes of checking, I decided it was a problem on the control circuit board (the ‘brains’). To access the control board, one must remove the refrigerator from the camper. That took about 90 minutes. It took another 30 minutes to remove the control board.

What did I find?

Well, it was quite annoying. There is a fuse on the control board that is inaccessible until one removes the circuit board. Worse yet, this fuse is smaller than the fuse in the easily accessible fuse panel. So, the hidden fuse will likely “blow” before the easily accessible fuse. This fuse had “blown”. But it was not due to a short circuit or an “overload”.

It was caused by a poor design.

The refrigerator’s 12 volt system uses 15 amps. The pieces that connect to the fuse on the control board have an absolute maximum rating of 15 amps. In the electronics world “absolute maximum rating” is something that must never be exceeded for any length of time, and it is best to operate things at less than “absolute maximum”.

It’s sort of like a car engine with “red line” on the tachometer. The “red line” is the absolute maximum rating and, obviously, one never keeps the engine at that speed for any length of time.

So, what happened. The connection, which was being used at “absolute maximum “, started to get hot. This caused the connection to become worse, which made the connection get even hotter…which caused the connection to get worse….and so on.

The fuse was charred and eventually got hot enough to melt inside of the fuse and the solder holding the fuse connections in place. The control board was also charred.

I reworked the fuse connections and replaced the fuse, so the refrigerator is working again on 12 volts, but I don’t think it will last very long.

I called a camper service/parts place to get the needed part ($250) and found out the manufacturer had extended the refrigerator warranty from the listed 1 year to 2 years. This camper is 20 months old. So, I put everything back together, kept the charred fuse and called to make a service appointment.

Had I known it was still under warranty, I would have just called for the service appointment.

I also found out the part is currently on backorder and is likely unavailable for the next 2-3 months. So, after they examine the unit and decide it really is bad, I’m making some modifications to the system so that the control board, even with the charring, will likely last for many years.

The control board will control a relay that I’m adding to the system. A relay is essentially a remote controlled switch that uses a small current to power an electromagnet in the relay and the electromagnet operates a switch capable of handling 30-40 amps of current. This relay needs about 0.1 amp from the control board, so the control board won’t be stressed. The relay will then do the “hard work” of switching the 15 amp current needed by the refrigerator, and since the relay is being used far below its ratings, it should last a very long time.

I paid $12 for the components.

Had the design used better parts to connect to the fuse (an extra 75 cents…I checked…..) or the $12 system I’m going to set up, this problem wouldn’t have happened. My guess is that the engineer knew this, but was told to minimize costs and build it “just good enough”…with just good enough being “lasts long enough to make it through the warranty before failing”.

Sigh…

Mom 1918-2016

Three posts in one day. I think this is a record for me.

While tomorrow is the anniversary of the US Marine Corps, today is the anniversary of my mother’s death. At just before 1pm, I went out and gently sounded 8 bells on the ships bell that I have placed in the back yard.

Mom and dad are buried next to each other at the Veteran’s cemetery. Dad was a US Marine Major. Mom was a US Navy Lieutenant.

Pest

This is the cat that adopted me just after I started at university. I found the picture while I was packing up stuff in preparation of moving.

I ended up calling her Pest. She slipped into the house while I was bringing in groceries and made herself at home. I gave her some food and I was suddenly a slave to an 18 pound/8kg cat that loved laying in laps.

Pest was an indoor-outdoor cat…after all, she had been taking car of herself without human assistance. I tried to convert her into an indoor only cat, but she was so miserable being stuck inside that I relented and let her go back to being an indoor-outdoor cat.

Her name came about when I discovered she loved to make a lot of noise at 2, 3 or sometimes 4am. If she was inside, she wanted out. If she was outside, she wanted in. Sometimes it just seemed like she wanted to make noise. People thought the name was “horrible” until the reason for the name was experienced first hand.

The first time she met my then girlfriend, she (the cat) went “crazy”; loud excited meowing, running around throughout the house, running between ankles, zooming over the top of the couch and then more running between ankles. It was difficult for my girlfriend to make it to a chair without tripping over or stepping on Pest. When my girlfriend finally was able to sit down, Pest jumped up into her lap, sat for a moment and then repeated the entire “show” before coming back and again laying down in her lap.

I would joke that it was as if my girlfriend was a bale of catnip as Pest was SUPER excited each time she came to the house. If Pest was outside and she saw my girlfriend show up, she would come running up to her as fast as she could run. After awhile, Pest would lay atop the roof of the house and look down the street in the direction that my fiancee would ride up on the bicycle.

Pest absolutely loved my fiancee and hers was the preferred lap to lay on, but even then, Pest would want out to go patrol the yard. This changed after surgery and during the cancer treatments. Suddenly, Pest was like “Velcro Cat”. She would lay beside where ever my fiancee was laying/sitting and only get down to eat, drink or use the litter box. Whatever it was, she would immediately jump back up beside my fiancee.

When I brought the blanket home from hospice, Pest started running around and after a few minutes of this, she jumped up on the blanket, looked around, meowed a bit and then settled onto the blanket. It took a month or so before she would leave the blanket for more than a few minutes at a time and after that, she returned to being an indoor-outdoor cat. I would see her laying on the roof…looking down the street….

Amazing

I find it amazing that it has been four years since I retired. November 1, 2017, my last day at the telephone company, I drove my 1950 Jeep to and from work…just like I did on my first day there in November 1991.

And, it’s also amazing that 38 years have passed since my fiancee’s doctor recommended hospice. I remembered that by going out on long slow run run. Running and cooking were our “time together”. We studied together as well, but that was more of an individual effort because engineering and pre-med/micro-biology did not have a lot of common classes.

Equally amazing is how my definition of a long and slow run has changed since the early 1980s. Sigh…

Hobbies

We are continuing to pack things up so we can sell the house and move elsewhere….elsewhere being somewhere “not hot” and “not city”.

As the packing goes on, the number of hobbies I can do become more limited. But, something that will not be packed up (for many years, I hope) are my running shoes..so I still have my trail running.

When I got home from the run, my wife told me, “You’re soaked. You STINK! Go shower!”

I guess I did work up a bit of a sweat. 🙂

Mother in Law

Last week, my mother in law had the PICC removed from her arm and yesterday she returned to her home.

She is the one who wanted to get back to her home and I understand that feeling. However, I do miss her being around. Unlike the stereotypical mother in law – son in law relationship, I very much enjoy her being at the house

One thing I did notice is her mental acuity and mood seems far better than it has been in the past several years and I think it has to do with her interacting with people. She is 84 and lives alone in her house. All of her friends are now dead, or have been “taken” be dementia and are now in a nursing home. Add the COVID-19 precautions and, to me, she has been merely existing.

My wife plays bluegrass music with 3 other people…a 60 year old man, the 90 year old father of the 60 year old man, and an 80 year old man. Myself, the wife of the 60 year old man and the wife of the 80 year old man come along to listen. The 90 year old man is a widower and is mentally *very* sharp–talking about everything from history and current events to politics.

We would always try to get my mother in law to come along with us, but it was always, “No. It’s too far out of your way and I don’t wan to be a bother”. This was despite our assurances that it was no bother to drive the 3 miles out of our way to go get her.

When she was here, the “3 miles” was not an available ‘excuse’, so she would come along with us.

Now, even with her being back at her home, she has said, “I hope you can come get me for the next jam. I enjoy them a lot.” My wife and I are thrilled.

They Don’t Know a Wall Fell

I was outside working in the yard when I saw a police car, with the emergency lights activated, pull up in front of a neighbor’s house and I saw the officer run into the house.

Less than a minute later, the fire department paramedics pulled up in the ambulance and the medics rushed inside with their their lifesaving equipment.

A minute later another police car arrives and the officer from this car walks into the house.

Ten minutes later, the paramedics leave and a fire department crisis response van arrives.

Twenty minutes later, a van, discretely marked “Medical Examiner”, arrives at the neighbor’s house. At his point, I see the first police officer, his head hung down, slowly walk out of the house, get into his car and sit there a few minutes before driving off. He wasn’t writing a report. He seemed to be collecting his thoughts before going on with the rest of his shift.

Soon, the medical examiner people go get a gurney from the van and take it inside. A few minutes after that, they are pushing the gurney back out to the van. This time I can tell the gurney is no longer empty.

It was the neighbor’s son. I knew him.

He had been in the army and had been in several combat engagements. When he came home, demons followed him. He fought his demons, but to no avail, so he tried building a wall, using whatever he could find, to provide cover from the demons.

He had been in and out of various acute care places and as soon as he was deemed “okay”, the demons would return…and he would start rebuilding his wall.

Today his wall fell on him. A drug overdose.


We live within walking distance of a high school and tonight the football team is playing at home. I can hear the band playing and I can hear the crowd cheering. Obviously the people cheering don’t know what happened just a short distance from the school.

Normally I would be part of the cheering crowd. But not tonight, because I know that a wall fell down.

PICC

Since my mother-in-law is home from hospital, some aspects of her continuing treatment fall upon my wife (her daughter) and myself (her son-in-law).

She gets 2 grams of an antibiotic each day through a PICC. A PICC is a long thin tube that is inserted into a vein in the left arm and the tube is pushed in far enough to end just above the heart. The other end of this tube is outside the skin and has valve on it. This valve closes automatically when there is no syringe attached…this prevents blood from coming out the PICC. There is also a clamp that gets closed unless the PICC is actively being used. The clamp is a backup in case the automatic valve fails.

In case you want to see what this whole thing looks like, searching for PICC with any of the internet search engines will show all sorts of descriptions and images.

The PICC has several things that need to be checked; no sign of infection where the tube exits her body, ensuring the tube doesn’t start to come out, that the end of the tube inside the body doesn’t become clogged by clotted blood.

The daily noon-time process takes about 15 minutes and is the same each day except for Monday. On Monday there is additionally a blood sample taken and the sample is sent to the medical testing lab.

The results of the lab analysis are sent to the physician so the physician can decide “what’s next”.