Actuator limit switch and RPi screw terminal breakout board installation.

 

I have installed a mechnical limit switch on the linear actuator. This switch will close when the actuator reaches the maximum point of retraction. A signal is sent to the Raspberry Pi computer informing the software the switch has been closed and maximum retraction has occurred.

The purpose of this is to prevent overloading that can occur when the actuator motor is still trying to retract after the retraction physical limit has been reached..

The overload occurs when the software boots and automatically performs a full retraction, and the actuator is already retracted.

A different problem is going to be addressed as well. The RPi has Dupont jumpers as connecting wires to other devices. These jumpers have a #28 AWG wire gauge. This is too fragile and difficukt to work with if soldering needs to be done. A screw terminal breakout board will allow dupont jumpers to connect the Pi to the terminal board and external devices with heavier gauge wire, to connect to the board using screw terminals. The terminal board is a 'hat' and plugs into the Pi.

Update on technology

The status of consumer two-axis tracking hardware is unchanged.
Elsewhere though, much has changed.

Solar panels are getting cheaper.
New technologies are making panels much more efficient.

These developments will effect the long term future of solar energy for residential consumers.

Excel translator

Hello,

   Someone has written an Excel formulas translator in the Python language.
Python is one of the languages used in my system. I'm going to explore the use of that software as a substitution for my transcription.
   If the program includes forward and reverse transformations, I may be able to save/convert data in excel format.

Backup everything

This post deals with an mportant topic: backups.

All equipment will eventually breakdown.

The only solution is to keep some sort of backup system in stock.
In my case, the current backup is a lower powered version of the present system. This will do until I get something with more power. The current backup will run my light and stereo, provided I don't play the stereo too loud.

I have spare cables and conectors for the solar station.
I have a 300w inverter and a 60A PWM controller.
Panels are not likely to go out or bad for over twenty years. Uless falling tree branches or speeding automobiles are an issue, there's no need for a full backup of panels, though one or two spare panels would be convenient.

If a component goes bad or is damaged beyond repair, I count on at least a week for a replacement to arrive. As an electronic engineering technician, I keep test and repair equipment on hand. I even have backups for those.

My batteries run about $150 each. My inverter runs $150-$250. The controller runs around $150.
If a cloudy day or two occur, I have a quiet 2000w gasoline generator that runs my system and charges the batteries, using an automobile battery charger. The batteries are marine grade dep discharge type.

Using a backup system as emergwncy aid is a good idea.

Actuator power relay switch

Actuator power relay switch installed.

   I ordered and received a two-relay card. I use a four-channel version to reverse the actuator power for forward and reverse movement.
   The two-channel unit controls the actuator power supply battery connection. This unit is controlled from the same script that moves the actuator, hence the solar array.
   When the script runs, now, the two-channel unit turns on and connects the battery bank to the boost converter. The boost converter boosts the battery voltage to that needed to drive the actuator, approximately 32vdc-36vdc.
   Previously, the unit was connected by manual operation of a mechanical switch.

Re-thinking the system

   The system is running well. There are some changes that are needed but are difficult to implement.
   Roof-top installations are the most popular now, but also the most inefficient. I opted for a single axis, sun tracking, ground mounted system. The most efficient is the two-axis tracking system. The hardware needed is being made, just not for consumers (complaint).
   Due to the lack of adequate hardware support by the industry, I've had to innovate my own single axis tracker. There are limitations in the range of movement in the panels. This can be increased by raising the system off the ground and/or adding a linear actuator with a longer reach.

   My current system uses one inch galvanized steel pipe as a mounting axis. Two rows of three panels each are mounted, one above the other. The pipe comes in ten foot lengths. The pipe is tilted at an optimum forty-five degrees, for this latitude. This creates a classic Pythagorean Isosceles  triangle.
The pipe forms the hypotenuse of the triangle. If I extend the length of the pie by adding a short segment to the bottom, one of the angles will change. To maintain the proportions, I will also have to raise the upper end of the pipe, and possibly add a similar short segment to the top end.

   I added a vertical ten foot section of strut to the left side to stabilise the upper and lower rows of panels. I need to add another to the left side.

   In thinking this over, I realize I could extend those struts and add at least one more row of panels to the top.

Of course, adding all this extra weight means I may need to replace the one inch pipe with a two inch pipe.

   I also consider adding a two foot extension to the bottom of the pipe.

   After all this, I'm reconsidering the use of concrete placed rectangular steel tubing along with fixtures to make a dual-axis tracker. The model for this is a unit on YouTube from a Chinese company. I have to consider whether the model is scalable, i.e. whether a larger model will hold more panels safely and scurely. Needless to say, cost is still a factor.

It's that time again.

Every so often, the Raspberry Pi orgnization issues a new release of the operating system for the Raspberry Pi. Most recently, and coincident with the debut of the Rapspberry Pi 4B+, is the Debian Buster operating system. Before Buster were Jessie and Stretch.

When a major update to the operating system is issued, I have to re-format the SD memory card.
Then install the memory image on the card. I have to add a couple of files in order to communicate with the RPi without using an external monitor and keyboard. I can go 'headless' and use my local wifi router and my laptop to run SSH sessions.

Once communications is established, I set some system parameters. Next, I begin downloading and installing programs and other software to run on the RPi.

This process, with testing, can take half a day or more. For this reason, I keep a backup of the SD card once I'm done with updates and modifications. This way, if a card goes bad or some damage occurs, I'll have a spare ready for installation. Just plug and run.