Now it's time to build the power signal generator test unit with a 8-bit controller.
The PIC18F14Q41 will the controller used because it has some nice analog functions.
https://www.microchip.com/en-us/pro...erals/integrated-analog/operational-amplifier
https://www.microchip.com/en-us/pro...dent-and-analog-peripherals/integrated-analog
8-bit DAC for sine wave generation
Digitally controlled OP amp for signal buffering and level control.

Using a simple 8-bit uint8_t sine table with a indexing loop we generate the analog signal in a timing loop of ASM nop instructions and volatile variables to stop optimization.

    while (true) {
        Nop();
        Nop();
        Nop();
        Nop();
        Nop();
        Nop();
        DAC2_SetOutput(sine_wave[sine_index = sine_index + (uint8_t)sine_skip]);
    }

// sine.h
#define sine_skip    4

const uint8_t sine_wave[256] = {
  0x80, 0x83, 0x86, 0x89, 0x8C, 0x90, 0x93, 0x96,
  0x99, 0x9C, 0x9F, 0xA2, 0xA5, 0xA8, 0xAB, 0xAE,
  0xB1, 0xB3, 0xB6, 0xB9, 0xBC, 0xBF, 0xC1, 0xC4,
  0xC7, 0xC9, 0xCC, 0xCE, 0xD1, 0xD3, 0xD5, 0xD8,
  0xDA, 0xDC, 0xDE, 0xE0, 0xE2, 0xE4, 0xE6, 0xE8,
  0xEA, 0xEB, 0xED, 0xEF, 0xF0, 0xF1, 0xF3, 0xF4,
  0xF5, 0xF6, 0xF8, 0xF9, 0xFA, 0xFA, 0xFB, 0xFC,
  0xFD, 0xFD, 0xFE, 0xFE, 0xFE, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0xFF, 0xFF, 0xFE, 0xFE, 0xFE, 0xFD,
  0xFD, 0xFC, 0xFB, 0xFA, 0xFA, 0xF9, 0xF8, 0xF6,
  0xF5, 0xF4, 0xF3, 0xF1, 0xF0, 0xEF, 0xED, 0xEB,
  0xEA, 0xE8, 0xE6, 0xE4, 0xE2, 0xE0, 0xDE, 0xDC,
  0xDA, 0xD8, 0xD5, 0xD3, 0xD1, 0xCE, 0xCC, 0xC9,
  0xC7, 0xC4, 0xC1, 0xBF, 0xBC, 0xB9, 0xB6, 0xB3,
  0xB1, 0xAE, 0xAB, 0xA8, 0xA5, 0xA2, 0x9F, 0x9C,
  0x99, 0x96, 0x93, 0x90, 0x8C, 0x89, 0x86, 0x83,
  0x80, 0x7D, 0x7A, 0x77, 0x74, 0x70, 0x6D, 0x6A,
  0x67, 0x64, 0x61, 0x5E, 0x5B, 0x58, 0x55, 0x52,
  0x4F, 0x4D, 0x4A, 0x47, 0x44, 0x41, 0x3F, 0x3C,
  0x39, 0x37, 0x34, 0x32, 0x2F, 0x2D, 0x2B, 0x28,
  0x26, 0x24, 0x22, 0x20, 0x1E, 0x1C, 0x1A, 0x18,
  0x16, 0x15, 0x13, 0x11, 0x10, 0x0F, 0x0D, 0x0C,
  0x0B, 0x0A, 0x08, 0x07, 0x06, 0x06, 0x05, 0x04,
  0x03, 0x03, 0x02, 0x02, 0x02, 0x01, 0x01, 0x01,
  0x01, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02, 0x03,
  0x03, 0x04, 0x05, 0x06, 0x06, 0x07, 0x08, 0x0A,
  0x0B, 0x0C, 0x0D, 0x0F, 0x10, 0x11, 0x13, 0x15,
  0x16, 0x18, 0x1A, 0x1C, 0x1E, 0x20, 0x22, 0x24,
  0x26, 0x28, 0x2B, 0x2D, 0x2F, 0x32, 0x34, 0x37,
  0x39, 0x3C, 0x3F, 0x41, 0x44, 0x47, 0x4A, 0x4D,
  0x4F, 0x52, 0x55, 0x58, 0x5B, 0x5E, 0x61, 0x64,
  0x67, 0x6A, 0x6D, 0x70, 0x74, 0x77, 0x7A, 0x7D
};

We don't need the full 8-bits to create a usable signal and it needs to be at least 9 kHz so we index by 4 for analog data steps.

Using MCC, we do a quick setup of DAC2

Config our DAC ref voltage for the analog level we need.

Config the OPA for the analog signal buffer output gains input/outputs we need. We can program the gain resistor ladder using a GPIO interrupt so we don't need to poll during our frequency timing loop.

The result is a usable signal (we can stop, start and adjust in amplitude) to feed a audio amplifier for the resonant magnetic wireless coupling loop.

What's left is to make a power, signal and HID interface prototype board and to tidy up a simple button/led user interface for a project box.

Then design a custom PCB instead of using one of my old designs made for serial protocol conversion.

 

...generate the analog signal in a timing loop of ASM nop instructions and volatile variables to stop optimization.

Or, NCO + DMA to eliminate the code entirely.

void DMA_start(void)
{

    DMA1SSA = (uint24_t) da_sin_tab;                    //Source Address:  Sin Sound Table
    DMA1SSZ = DAC_SINTABLE_SIZE;                        //Source Size:     32
     
    DMA1DSA = (uint16_t) &DAC1CON1;                     //Dest Address:   DAC1
    DMA1DSZ = 1;                                        //Dest Size:       1

    DMA1CON1 = INIT_DMA1CON1;
    DMA1SIRQ = INIT_DMA1SIRQ;                           ////NCO Interrupt triggers transfer

    //Set PRLOCKED bit to grant memory access to DMA
    INTCON0bits.GIE = 0;
    PRLOCK = 0x55;
    PRLOCK = 0xAA;
    PRLOCKbits.PRLOCKED = 1;
    INTCON0bits.GIE = 1;

    //Enable & Start DMA transfer
    DMA1CON0 = INIT_DMA1CON0;
}

 

Or, NCO + DMA to eliminate the code entirely.

void DMA_start(void)
{

    DMA1SSA = (uint24_t) da_sin_tab;        //Source Address:  Sin Sound Table
    DMA1SSZ = DAC_SINTABLE_SIZE;          //Source Size:     32
  
    DMA1DSA = (uint16_t) &DAC1CON1;                      //Dest Address:   DAC1
    DMA1DSZ = 1;                             //Dest Size:       1

    DMA1CON1 = INIT_DMA1CON1;
    DMA1SIRQ = INIT_DMA1SIRQ;
  

    //Set PRLOCKED bit to grant memory access to DMA
    INTCON0bits.GIE = 0;
    PRLOCK = 0x55;
    PRLOCK = 0xAA;
    PRLOCKbits.PRLOCKED = 1;
    INTCON0bits.GIE = 1;

  
    //Enable & Start DMA transfer
    DMA1CON0 = INIT_DMA1CON0;
}

+1

Bravo, the original application of that board used DMA for several functions of RS232 IN/OUT conversions and SPI displays.

I'm mainly using old school cpu wasting delay loops because the application is a dumb One Trick Pony.

 

Don't' want to go too OT, but
https://ww1.microchip.com/downloads/en/appnotes/00001523a.pdf
Sine Wave Generator Using Numerically Controlled Oscillator Module

The DDS method of signal generation is pretty cool. I've used it (software) on the RPI with a custom kernel driver I wrote.
https://forum.allaboutcircuits.com/threads/creating-sine-wave-using-dac.133949/post-1115671

https://forum.allaboutcircuits.com/...c-and-xy-axis-on-my-scope.155253/post-1340739

 

Looks good as the wireless system signal generator, time to wrap it up.

RC filtered output.

Transport car operating voltage @90% amp power.


Blue C2: Signal generator output.
Yellow C1: Sony amp output.
Shows signal delay phase shift.

FFT of C1 Sony amp output from matching coil signal monitor loop using the PIC18 signal generator.

 

Done.

 

Cover for the matching coil.


Power usage profiles. Car at nominal voltage.

Idle power of Sony amp.

 

Repaired a Karcher WV50 window power vacuum.



The internal lithium 18650 battery was not charging higher than 3.2V.
Water got inside and corroded a trace on the PCB. You would have thought that the manufacturer would have used conformal coating on the board.

 

Repaired my vulgar GE microwave oven. Bad door latch microswitch replaced.
Failure of that by arcing its contacts or blown fuse from fractions of a millisecond are from opening the door instead of ending cycle.
No downtime cooking as I keep the huge mid seventies Radarange Touchmatic in the basement as emergency backup, still working like a champion 50 years after. :

Enough steel and chrome to make a Honda recycling it...

 

You would have thought that the manufacturer would have used conformal coating on the board.

Why? The Chinese got your money anyway.

 

Why? The Chinese got your money anyway.

Wasn't mine. I volunteer at two local Repair Cafes where we divert home appliances from landfill by doing repairs at no charge. We try to promote the 4 Rs - Reduce, Reuse, Recycle, Repair.

 

Blum 170 Degree hinge.


Yes, real hickory solid wood doors. That wood loves to split.

 

Trying to repair but may replace: The hydraulic door closer on a business partner's take-out restaurant. It has many "adjustment screws" with no markings, and it seems also to have lost some oil.
Aside from that also trying to diagnose a HEATHKIT "SW7800" Receiver. It makes sounds like it is receiving but does not pick up anything. Among other projects.

 

Hamilton Beach SC42 slow cooker

Symptoms: no signs of life, no heat, no display. The LED display should show OFF when the unit is plugged in.

Found shorted 470μF/16V capacitor in the low voltage supply. Capacitors don't like being hot.
Replaced with 470μF/35V capacitor.
Strangely, there is no fuse nor thermal circuit breaker in this unit.

 

Photo of our most recent local repair cafe:




Local repair cafe at another location yesterday

 

HEATHKIT "SW7800"

According to www.findchips.com they have them for 16 dollar 1+ 12 dollar 4+ at quest components.
MC1496G metal 10 pin can
they also come in 14 pin ceramic (3 dollar) and SOIC case (0.5 dollar) versions.

https://mirror.unpad.ac.id/orari/library/library-sw-hw/community-broadcasting/datasheet/mc1496.htm
here they compare the connections.
The MC1496P are doubled balanced modulator-de- modulators - Wide frequency response up to 100 MHz
Heathkit SW-7800 Shortwave Rebuild: http://schmitzplace.com/Johns_Electronics_04.htm
(Seems a lot of work if you do it this thorough, on his site I)
https://forums.radioreference.com/threads/heathkit-sw-7800-questions-suggestions.261810/
they say something about the quality of the receiver.
Better supply:

Good Luck with it.

 

On an old house from 1940, repaired a twist mechanical trough-the-door rustic victorian doorbell. Adapted a missing bronze knob and shaft, made a square shaft, threaded it to secure the knob, threaded to hold at the bell end; It works.


Image from similar borrowed from the web.
Edited: Something is in doubt. It is held to the door with bronze philips screws... I think they were not invented yet then.

 

Repaired a Curtis Stone air fryer.



One LED was bad causing three other LEDs to be permanently on.

 

https://forum.allaboutcircuits.com/threads/board-burns.153544/post-1912814
Power supply.

 

Desoldered a 48-pin through-hole connector from a PTH pcb. Both connector and pcb are resuable. (My colleague can now put the correct connector in the correct pcb)