OpenSprinkler Forums Hardware Questions DIY Kit Assembly Questions LCD is backlit but characters are rectangles

This topic contains 17 replies, has 6 voices, and was last updated by  TheDeadly1 3 years, 11 months ago.

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    Howdy thisisit. I have been exceptionally busy over the last month, so I haven’t been able to troubleshoot my PCBs to my satisfaction. They have been sitting idle for a few weeks with no resolution.

    I don’t know your technical expertise, but I can tell you what my approach will be when I resume troubleshooting these PCBs in a few weeks. My ethernet section (the ENC28J60, the RJ45 jack and all the discrete components) appears fully functional, as does the power supply section. I’m not concerned that the triacs don’t actuate at this point. I am concerned about the data lines on the µC that are driving the LCD, the 74HC595N and the relay (the sections that are non-functional). It would be very interesting to wire the µC (and associated circuitry) and the LCD separately on a breadboard and see if the LCD functions. It may be that there was something on the PCB that was dragging down a data line or two. That could also be simulated by carefully bending pins up on the µC and reinserting it into it’s socket. My USB section (or rather it’s communication with the µC) is also suspect. The CH340G ICs I bought from China came in a non-ESD bag from the vendor, so its possible that some have been damaged, including the one I installed.

    I wanted to thank you for your inquiry, as it has renewed my interest in repairing my PCBs and rehashing my previous efforts has also given me a few more things to try, including isolating the µC from the:
    • CH340G
    • DS1307
    • Relay circuit
    • SD card socket
    • Valve driver circuit

    Good luck and please post your findings. It may just help someone else.




    In my case, my CH340G is also working, I can update the firmware via USB. Just the LCD and the valves are not working. I haven’t tried the relay yet but I assume it is not working.

    I doubt it has anything to do with the circuit trace, I have checked the connectivities multiple times using a multi meter. I suspected the µC, I have reprogrammed it, also replaced it, still the same thing.

    So I can borrow a o’scope, do you know what to look for using an o’scope?




    Howdy thisisit,
    sorry for the late reply….busy weekend.

    I’m going to be inquiring at my local maker-space this evening about the availability of an oscilloscope. In lieu of that, I have my eye on a Tektronix TBS1052B-EDU 50 MHz, 2 Digital Channel Oscilloscope at Amazon or a PC-based unit. So, what we’re looking for with the scope is not necessarily specific data that is being exchanged on any particular data line, but merely the quality of the signal being exchanged. Specifically, I want to see nice edges from all address and data lines (i.e. – google+images “square wave”) and no signals that look like they are ramping up to near Vcc (i.e. – google+images “capacitor charging square wave”). If there is something up with a data line or multiple lines, trace it/them until you find the issue. It’s quite possible to find solder bridges that tie data lines together or a data line to some other part of the circuit. Solder bridges love to hide under connectors and other parts. If all of the µC pins look OK, I would measure all of the MOVs (V0-V9) for resistance and also remove the LCD and see if the valves actuate using the web interface. My next step would be to start isolating the sections I mentioned in my last post. Depending on your skill with a soldering iron, you could easily lift pins to the µC on IC5, IC4, U1, IC3 & resistor RQ (in that order). Post back your findings and if you have any more questions.

    Good Luck

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OpenSprinkler Forums Hardware Questions DIY Kit Assembly Questions LCD is backlit but characters are rectangles