SSR development and new image processing scripts

The last post, I outlined the options for adding a solid state relay (SSR) to my system as a replacement for electro-mechanical relays. 

PCBs & SSRs

I've been exploring all, simultaneously. The mateials and methods for diy pcb manufacture are all but complete. The acid comes from a battery that failed in my solar station. The acid, surprisingly, is self renewing if time and hydrogen peroxide are added. The remaing block is the drawing tool. Permanent markers work, to a certain degree, but chemical reactions have to be monitored or too much copper etch could be removed.

I've also been using the EasyEDA system for pcb design and manufacture. If the software were more user friendly, the process would be an obvious choice, given the price.

The third front is a purchased ready-made pcb. This is possible and affordable since I only need one. However, the sellers come and go and there's no guarantee the same seller/product will be available should the unit fail. The cure is to stick with well estblished and well known companies, which also means a substantial increase in costs. I ordered a pcb which was not entirely ready, and made a couple of modifications to make the unit ready. Unfortunately, an input LED was crushed and the circuitry is SMT.

SMT is miniature parts machine placed and soldered, unless you have the hands of a neurosurgeon.

IMAGE PROCESSING SCRIPTS

I wrote and tested a script that runs as part of an existing linux service on the Raspberry Pi.

Each day, the script is called and creates an image from the day's csv data file. The image is moved to a folder made for the imges.

My system began around 2016. Not much later, I began collecting and saving the data in the form of comma separated values (csv) files. Subsequently, I've accumulated a lot of them.

I developed and tested a script to batch process a folder full of csv files. The script works with one hitch. Recently, an occasional blip in the data will occur. This will cause the script to halt. I do a CTR-C and respond to the "contnue?" query with a yes. The script skips the problem file and continues processing the folder. There is a scrijpt that examines the csv files and deletes partial, incomplete lines . I need to finish that and incorporate the script into an existing daily linux service.

NOTE: for some reason, my Raspberry Pi 3B+ crashed and is not useable anymore. I've programmed the Raspberry Pi 4B I've had in storage, as a replacement.

PCB design and construction

 The SSR mentioned in the last post requires a printed circuit board (PCB).  There are several options.

1. outsource the task and let a company take my data and print the needed boards..

2. make the boards myself. The options expand profusely at this point.

    a. presensitized boards and photo etching

    b. standard  boards and 'iron on' process

        1. with or without lamination

    c. choice of laserjet or inkjet printer

There is much to consider and the choices will not be made in this post. 

Time will tell.

SSR

 

   I'm replacing my custom wired relays with SSRs (solid state relays).

  Traditional relays are electro-mechanical in nature. A coil is energized causing contacts to open or close. The equivalent of  such a coil is referred to as a 'solenoid.'

   All such devices make noise and are susceptible to mechanical wear and corrosion and welding of contacts.

   The SSR is composed of  semiconductor devices, typically, mosfets (metal oxide semiconductor field effect transistors).

   In my design, opto-couplers turn the mosfets on or off. A low power signal is isolated from the mosfet circiutry using these devices. The design and construction is more complex than the relays, but is more reliable, quieter, and can handle more power per dollar cost.

The design I'm using is here:

The first is the linear actuator motor control. The second includes the actuator power supply on/off switch.

Linear Actuator reprise.

    For the last couple of years, the solar array has been stationary and the motor not used. A relay card, rewired by me, burnt up. The actuator motor drew too much current for the copper etch traces when the actuator reached the limit of movement and increased current flow.

   I've installed a limit switch to help prevent future failures. I an also installing solid state relays with a rating almost three times the maximum  required by the actuator motor.

   For the last few days, I've been researching SSR's ( solid state relay). I ran across a suitable design that uses mosfet semiconductors and opto-couplers.

   All day, today, I've been breadboarding and testing circuits. I have prototyped and tested the design I want to use with positive results.

   The next step will be to assemble the final breadboard circuit and install on the Raspberry Pi 3B. The new circuit replaces the custom-wired quad-relay card. The mechanical aspect will be no longer an issue. No welded contacts. No custom wiring. No burnt etch traces.

   The parts come from my stock parts stores with some coming from a Samlex Cotek 1500w inverter that stopped working years ago.

   The extra solar energy will come in handy this winter.

The importance of backup systems.

 Last week, my charge controller pooped out. I decided to replace my inverter too, while I was doing maintenance.

I replaced the charge controller with a Xantrex C60 PWM charge controller. The PWM charge controller is not to be confused with the Xantrex PWM inverter.

I received the pure sine inverter and replaced the PWM inverter.

When the new charge controller arrives, the Xantrex PWM charge controller will go back into storage. The Xantrex inverter, paired with the Xantrex charge controller, will make up a backup system. I also have a backup Raspberry Pi SoC (System on a Card) system data logger and array position controller.

I will have had a system failure and maintained household power availability. This illustrates the importance of backup systems and components.

Inverter poops out.

 Woke up one morning and the Epever Tracer 3210 had quit working.

I got on eBay and started searching. I discovered a newer model, from the same company, with higher current rating.

The Epever Triron 4210 was advertised with a repairable defect. The price was better than I expected. The unit is in the mail and should arrive Wednesday. 

The newer model should be a plugin replacement that requires no modification to the existing software/hardware setup.

Inverter - Modified sine and Pure/true sine

 I decided, recently, to replace the existing Xantrex PWM inverter with a pure sine inverter. The output of the latter is closest to that produced by municipal utilities.

The replacement is a Samlex 2000. That unit is rated for 2000 watts where the Xantrex is rated for 1500 watts.

According to my research, the new unit will be more efficient and produce a better performance from connected devices.

The one thing I dislike is the noise. A fan runs continuously and is noisy. Power is used up unnecessarily. For this reason, I have to turn the power off every night.

I need to rework the fan design or setup automated power boot control.

Alternatively, I could create two different house wiring systems: one for pure sine devices and one for devices using PWM.