Battery charger damage and repair

  An old Schumacher automobile battery charger has been used to charge the system auto batteries , for several years. One day, a couple of weeks ago, the charge went pffft. When I tried to plug the unit into the wall a grinding noise was heard. I took the thing apart. The construction was surprising. There are two button diodes used as rectifiers. One had shorted. I replaced both with standard through-hole tech diodes and reassembled the unit. Functional status restored.

Updated System Test run

 A lot of work needed to be done, but the testing was completed. 

The re-worked mosfet PCB functioned as a H-bridge reversible motor driver. But, during the testing, in the cramped space, I shorted out the PCB and blew out the Q4 mosfet. The PCB uses SMD technology which involves miniature components that lay flat on the board. Repair is therefore beyond my capability. Little experience and none of the specialized equipment. I'm trained in old school through-hole technology. Components are large enough to be inserted into holes on the board, then soldered. The new components have to be placed using tweezers.

 I'm waiting on a different design I ordered several days ago. The new PC will not require re-working, plus the new PCB uses through-hole technology, so repairs/upgrades, by me, will be possible.

One of the draw backs was the thin hook-up wire commonly used in prototyping designs. There are several wires running between the driver and other units. These broke three times. Frustrating is to say the least about the problem. I need to get some smaller gauge wire or consider using stranded wire.

The level shifting buffers worked and remain in place and ready. The limit switch software is tested and working.

I removed, tested, oiled, and re-placed the linear actuator.

Several short scripts were written and tested for use in testing the actuator.

The new driver PCB will arrive around the 12th. Waiting.

The last detail (?)

 The last detail is the hookup  of the limit switch to the system.

There are a number of reputable sources with apparent conflicting or inconsistent information. One resistor, two resistors, no resistors. 

I finally decided that a direct connection of the switch between 3.3VDC and ground with use of internal pull-up/-down resistors was what I would use.

Tomorrow, I'll do a trial run of the system.

All but done with linear actuator drive circuitry.

 The tests are done but for the actual hookup of the new  circuitry to the LA36 linear actuator.

Some changes needed to be made. A minor problem is the cheap hookup wire. Bend it a few times and it breaks. The grounds had to be isolated on the H-bridge inputs. One ground connection from one level shifter to one H-bridge input. 

I mention the small parallel mosfet boards, with no input isolation, in an earlier post. A couple of those boards are being used as level shifters to convert the raspberry pi 3.3VDC GPIO output to the 5VDC needed to drive the H-bridge inputs. The 5VDC also comes from the raspberry pi.

The ground jumpers I had originally installed on the H-bridge inputs, to create a common and shared ground reference, needed to be removed. This was the last hardware modification. 

Next, I need ti incorporate the forward, reverse, and off python scripts into the LA36 driver script.

The image show the new circuitry/PCBs. The level shifter are top left and the H-bridge is bottom left.

Real world adaptation - SSR

 Recently, I breadboarded and tested a four-channel mosfet pcb. The channels were not, as I had hoped, isolated, but share a common ground reference.

I made some changes and got the unit working as a reversible H-bridge motor driver.

However, after I installed the unit on the power panel, I discovered the unit was not functioning as expected. I ran some in-circuit tests on the pcb and everything seemed okay.

My observations of the unit led me to believe the opto-isolators were not being driven high enough by the RPi 3.3VDC GPIO pins. My last test was to substitute the 3.3VDC with the 5VDC, also from the RPi. Success. Now I'm examing the parallel mosfet pcbs I purchased earlier and rejected due to having no opto-isolator input buffer protection. Since those pcbs will drive an existing opto-isolator, there should be no problem.

The proposed level shifter pcb circuit:

Interim Linear Actuator driver pcb

 

   I purchased a Chinese four channel mosfet pcb on eBay. As it turned out, the chanels are not isolated from each other but share a common reference ground.

   Recently, I realized I could modify the pcb and use as a reversible H-bridge motor driver. Previouly, I had considered a different design but decided to discard the design. There was no 'off' position. One direction or the other would  always be 'on.'

   Currently, the Qg of 1,4 are tied together as are the Qg of 2,3. This allows only two control signals to run the driver. There is a combination of the two control signals that will allow an 'off' position.

   The Qs of  1,3 were lifted from the pcb and soldered to their respective followers; Q1s --> Q2d and Q3s --> Q4d. This created the necessarily isolation for H-bridge use.

   The images below are before and after using the LSpice XVII simulator. I've not run the simulator yet, but I have successfully built and tested the circuit on my Heathkit breadboard lab.

Before:

After:

Disaster, almost

 

Lightning hits the solar station.

   Saturday afternoon, September 9 (2023), lightning struck my solar station.

   I happened to be looking at the indoor power panel, when the bolt struck. There was a flash of light, the clap of thunder quickly followed by a popping noise at the panel and a small flash.

   I waited till the storm abated and disconnected everything. The inverter, which converts battery power to household power, began to whine. The internal alarm had been set off by the strike.

   I reconnected everything to a smaller backup inverter and examined the main inverter. There appeared to be no other damage other than the overload light which was continuously on. I think the light was also affected by the strike. 

   This morning, I reconnected the unit after a thorough examination. I disconnected the alarm during the examination and am going to give the unit a real world test. My theory is the unit will function as before, excepting the protection circuitry.

   The reason the damage was not greater, I believe,  is due to the nature of my station construction.

   The panels are bolted to a steel pipe which leans against a 2"x6"x8' piece of lumber. The lumber is attached to an aluminum ladder. The only part of the panels made of metal, are the frames. The cable running to the house is supported by steel aircraft cable attached on one end to a pvc pipe and on the other to a bracket bolted to the side of my house.

   I think the bolt struck the steel cable and jumped to the ladder and ground as well as my indoor power panel. That would explain the minimal damage.

   I need to ground the cable by making the circuit from cable to ladder, to earth ground, continuous by connecting the cable to the ladder and the ladder to a rod driven into the ground.

Everything's back to normal after I disconnected the inverter alarm. I examined the outdoor part of the station and found nothing. The line from the array to the house was sagging so I tightened the supporting cable while I was at it.

BOOM!!!