| Electronics > Repair |
| Korad KA3005P power supply faulty/repair |
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| Andreas:
--- Quote from: Tony Mach on August 03, 2017, 01:57:51 pm ---This is a economic PSU, it has no relay for the output. Very economic. (One more reason I would want to write my own software, to add a relay for the output… the control-board even has an output for such a relay.) --- End quote --- Hello, I have 4 of the units (2 * KA3005D and 2*KA3005P). All 4 have a output relay. So either you have a KD3005 or something is wrong. With best regards Andreas |
| Tony Mach:
Well, I definitely have a KA3005D, and no output relay. Please be advised, there are (at least) 3 version: - The "old" version, that eevblog initially tested (only one capacitor on the power-PCB) - The "middle" version, with updated PCBs (three capacitors on the power-PCB) - The "new" version which has among other changes "screw type" connectors for the output (the old/middle had "plug only" connectors for the output) I have the "middle" version. It has 2 relays for switching of the windings, but no output relay. Meanwhile, I now have a first version of my software that can access the two DACs (for voltage and current), and I can switch the output voltage in software – while I have not figured the DACs out completely (and might still have a bug or two), I think the hardware should be OK. This must have been a configuration problem. :wtf: Achievement unlocked: 74HC595 Achievement unlocked: Control the seven segment display Achievement unlocked: Control the DACs As I can get voltage and current out of the PSU, if I either manually set the control voltage, or if I set the DACs in software – without switching any relays in both cases – I am quite certain that there is no output relay in my KA3005D. I even looked and visually checked all the PCBs – I did find only the 2 relays for the windings on the rear PCB, there is no output relay in the path. I am curious: Where is this output-relay in your PSUs? On the power-PCB? Or on that little connector-PCB? On the main-PCB? Anyway, my software needs further work… Once more onto the breach! :-/O |
| Andreas:
Ok you are right, the clicking that I hear is from the transformer switching when I set the voltage above 5V. (What I usally do). With best regards Andreas |
| Tony Mach:
Hello Andreas, when you go above 5V, you hear one of the "windings relays"! Both winding relay are connected in such a way that there is always a connection from the transformer to the power electronics. The only thing that selects an output of 0 Volt is the control voltage. If this control voltage fails (e.g. faulty DAC), or if the winding relay fail (happened to one person, there is a video on youtube), you will get voltage on the output. Unfortunately there is no output relay. Kindest regards. Tony Anyway, I made further progress! The SHCP and STCP are mislabel on the processor end… :palm: I spend at least 2 hours trying to figure out why my 74HC595 routine did not quite work with the DACs 75HC595s… The same routine worked just fine with the LEDs 75HC595. :wtf: They mislabelled these two pins on the schematic… :scared: But now I can control the DACs!!! 8) Achievement unlocked: Output hexadecimal numbers on the LEDs Achievement unlocked: Control the DACs Onwards to success! :-/O |
| Tony Mach:
Well, I reached a crucial point with my firmware for my KA3005: The basic functionality (and everything needed for this) is working!!! I can adjust voltage and current, and the respective values are displayed! :-DMM It took a little longer than I thought to reach this point – but hey, I do this in my spare time, for free and for fun (at least my tortured sense of fun)… There is a metric ton of caveats attached to this firmware: * This works on my KA3005 - other hardware revisions may have critical differences (There is much strangeness in the schematic…) * AFAIK one can not read out the original firmware - so once you overwrite the original firmware you can not go back * There is no calibration routine, the calibration values are hardcoded * CooCox and the debugger are strange… Relays sometimes switch when you load new firmware – this contributed to me having once shot the power transistors :-BROKE The firmware was broken, so I wrote a new firmware, which broke the PSU - talk about irony… (But hey, I bought new transistors, fixed it :-/O and learned an important lesson: Do not leave a load like a 12V 100W bulb attached when the debugger is attached - detach any bigger electrical load before you load a new firmware. A 230V 50W bulb on the other hand is fine.) * I make mistakes (I once reached a peak value late at night of 2 bugs per 1 line of code) – this also contributed to the aforementioned incident where I shot the power transistors :palm: But now the switching of the relays should be solid. * Memory is not implemented (M1 to M5 not done) * The interface to USB/serial is not implemented (my PSU model is without the interface board, and one would need to reverse-engineer the protocol, so this maybe will never happen) * The keys are not debounced * No LOCK, no OVP, no OCP * The LEDs flicker under certain conditions (I know how to fix that, but haven't had the time to do it…) * Haven't fully figured out the temperature-ADC yet * Fan is switched on with the output, and runs aways with full speed while output is on * Other problems I forgot * Source code needs clean-up * No warranties whatsoever * No buzzer But there are also good things: * No buzzer * IMHO the adjustment of voltage and of the current is nicer in my firmware (and I might improve it even further by a little bit) * Considering the power rating of the transformer, and of the transistors, I think it could be possible in future to "overdrive" the PSU and output more voltage, or possibly even more current, under certain circumstances (if one stays within the ratings of those components) * One could implement custom behaviour (e.g. "soft start", or specialized battery charger, or or or …) * One could add an output relay, or maybe even an MOSFET as an output switch If you want to use this firmware, you need CooCox (I used 2.0.7, but other versions should do fine). I had to add cmsis_core, M051_BSP_CMSIS_V300_001 and C_library to my project (the C_library might not be necessary - the boilerplate I used needed it, but I haven't checked if I still need it). Sorry, no pre-compiled binary from me, no turn-key project – if you want to use this experimental firmware, you need to know what you are doing. Have fun tinkering! :-/O I might continue working on some of the missing features, but I do not promise anything. :P |
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