Here’s the MT50 controller from EpEver, that interfaces with it’s Tracer MPPT solar charge controllers, and gives access to more programming options on the charge controllers, without the need for a laptop. The display is a large dot-matrix unit, with built in backlight. Above is the display on the default page, showing power information for the entire system.
The rear plastic cover is held in place by 4 machine screws, which thread into brass inserts in the plastic frame – nice high quality touch on the design here, no cheap self tapping plastic screws. Both power & data arrive via an Ethernet cable, but the communication here is RS-485, and not compatible with Ethernet! The PCB is pretty sparse, with comms & power on the left, LCD connection in the centre, and the microcontroller on the right.
On the left of the board is the RS0485 transceiver, and a small voltage regulator. There’s also a spot for a DC barrel jack, which isn’t included in this model for local power supply.
The other side of the board holds the main microcontroller which communicates with the charge controller. This is a STM32F051K8 from ST Microelectronics. With a 48MHz ARM Cortex M0 core, and up to 64K of flash, this is a pretty powerful MCU that has very little to do in this application.
The front of the PCB has the ENIG contacts of the front panel buttons, and the LCD backlight assembly. There’s nothing else under the plastic backlight spreader either.
The front case holds the LCD module in place with glue, and the rubber buttons are placed underneath, which is heat staked in place.
The LCD is a YC1420840CS6 from eCen in China. Couldn’t find much out about this specific LCD.
I was recently given a pretty nice LED backlit 1080p LG monitor, with the instruction that it wouldn’t power on correctly. The monitor would power on as far as the standby light, but when fully powered on, would flash the backlight momentarily then shut down. A power supply issue was immediately suspected.
I popped the covers off the monitor itself first, thinking that it was an electrolytic gone bad in the backlight DC-DC converter. Not to mention the fact that cracking into a wall-wart type of PSU is only occasionally possible without the use of anger & large hammers. (Cracking the glue with the handle of a screwdriver doesn’t work so well when the factory went a bit nuts with the glue/ultrasonic welder). As can be seen in the photo, there’s not much inside these monitors, the logic is a single-chip solution, the rest of the PCB is dedicated to supplying the power rails for the various circuits. On the left is the power input & the DC-DC converter for the backlight, along with the DC-DC converter supplying the logic circuits. None of the capacitors here are damaged, everything looks good.
I then measured the output of the PSU, which under no load was the correct 19v DC. However applying any load caused the output voltage to drop like a proverbial brick. Applying a full load of 1.3A saw the output voltage drop so severely that the PSU tripped on it’s UVLO.
At 200mA of load the factory PSU is already dropping to 18v, with a 5.3kHz switching frequency appearing.
At higher load the frequency increases to 11.5kHz & the output voltage has dropped to 11.86v!
750mA was as high as I could make the supply go without it tripping itself out – the UVLO circuit trips at 9v. 12.6kHz is now riding on the severely low DC at this point.
The power supply is supposed to be rated at 1.3A at 19v, however with this fault it’s getting nowhere near that. The LG brand is on this PSU but it’s contracted out to Shenzen Honor Electric Co. Ltd.
Here’s the problem with this PSU. The output electrolytic has ballooned. I don’t have an ESR tester, but this cap has gone way past it’s sell-by date. It’s position right next to the heatsink with the output rectifier diodes has probably cooked it. The PSU isn’t that badly built for a Chinese one – there’s plenty of creepage distance on the PCB & even a couple of isolation slots.
On the quest to get things on board replaced that are heavy users of power, the monitor in the main cabin was next. The original CCFL-backlit monitor was very heavy on 12v power, at 5A. This meant falling asleep watching TV would result in severely flattened batteries.
Replacement with a suitable LED-backlit monitor was definitely required. The cheapest on eBay was a ViewSonic VA2232W-LED, so I took to work converting it from 240v to 12v operation.
There are no screws holding these monitors together, so a spudger & frequent swearing got the back off. The shield holding the circuitry is also not screwed down, only attached to the back of the LCD panel with aluminium shielding tape.
Once the tape has been cut, the main power board is accessible. The large IC on the left is the main backlight LED driver.
In this case the monitor requires a pair of rails from the supply, 18.5v for the backlight circuitry & 5v for the logic.
A pair of DC-DC converters has been fitted in the small space between the power & control boards.
To save me some work & keep maximum compatibility, I’ve not modified the existing supply, just attached the new DC-DC converter outputs onto the corresponding outputs of the factory PSU. The 12v input leads are routed out of the same gap as the mains IEC connector, with some hot glue over the mains input solder points to provide some more insulation.
The wiring is tidied up with hot glue so the back cover will go back on.