| Electronics > Repair |
| Korad KA3005P power supply faulty/repair |
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| Kleinstein:
It depends on the hardware and desired functions how complicated it would get wirting your own software. The main part could very well be interfacing the LCD output. Controlling the DAC / ADC should be relatively straight forward, unless they used the µC and a few external parts to implement a kind of high resolution sigma delta of other integrating ADC. Before deciding on the software, one should have a better picture on the actual hardware to control. AFIAK there is a chain of 74HC(T)595 used as a shift register for a R2R type DAC. So one might be a able to check the serial signal - just in case the trouble is not with the MCU. One could also check just the output of the R2R chain - this should be relatively easy to identify on the board. Edit: Looks like there are schematics available. No more than just the DAC, even the ADCs and display seem to be external. So if really needed, the software would be relatively simple. It would really worth looking at the DACs output, to exclude a problem with the control OPs. |
| Andreas:
Hello Tony, is the output relay clicking when you activate the output? With best regards Andreas |
| Tony Mach:
@Andreas: 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.) @Kleinstein: I have no isolation transformer, and the mains-switch is on the frontpanel – very near to the R2R DAC … I am so tempted to write my own software (even if this PSU has an hardware fault – it would be easier to pin down the fault if I know what I output). The main task would be to learn how to I/O on a Nuvoton with CooCox (there is some support in CooCox, but I'm an AVR32 guy, and everything in this new world feels slightly strange…) Otherwise the tasks would be: - Setting of the DAC (outputting with the 7495s) - Output via LEDs (as well 7495s) - Input of the wheel (interrupts?) and buttons (button matrix?) - General "user interface" - Reading the ADC for the voltage and current - Switching the relays for the windings (voltage "preselect") - Overcurrent handling - Some calibration routines - Reading/writing to the I2C EEPROM Other niceties (which can wait) include: - Reading the temperature and adjusting the fan - Buzzer - Output Relay - Use of M5 LED to display "LOCKED" - I/O via serial interface … Yeah, very doable. :-/O I just need to get started… :-DD |
| Kleinstein:
If you don't won't to poke around the circuit when life, one can usually solder wires to the test-points and connect everything to a DMM / scope before powering up. If the mains switch is so close to the logic part, one should consider insulation (e.g. heat shrink or similar) anyway. The µC is supposed to be ARM M0 based. AFAIK it takes some time to get used to the a new type of µC. A first point would be to decide on what type of support files (e.g. HW definitions as C include files) to use. Often there are kind of higher level version with special macros for initialization - however some of these systems are controversial. So some use the higher level interface and some only the register names. The biggest part is likely getting started to get a first program. |
| Tony Mach:
Every solder point I touch brings a PCB closer to death… I'm more a software person… So I'm glad the debug connection is working. Anyway, I got a "hello world" to compile in CooCox for the M054 with setting of one GPIO (for the fan). So after I successfully compiled, I could not resist, and the original firmware is already GOOOONNNE !!! The first I did was to switch the fan (P4.1) between full speed and low speed, which was surprisingly easy. I just added the switch of the columns (P1.4-P1.6 and P4.2) of the LEDs. I am making unreasonably fast progress… I smell a trap. :P Next I have a date with the 7495 shift registers – something I have been looking forward to do long before I met the Korad PSU. |
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