Introduction
Features
Video Demo
Device Operation
PSoC Configuration
Programming
Potential Applications
Conclusion
References

Published March 1, 2023 © CC BY-SA

PSoC4: CapSense based Portable Power Supply

CapSense Touch based HMI device to control power flow of high current DC loads with adjustable voltage control & current limiting feature

BeginnerFull instructions provided6 hours173

PSoC4: CapSense based Portable Power Supply

Things used in this project

Hardware components

Cypress PSoC 4 Prototyping Kit

Software apps and online services

Cypress PSoC Creator

Hand tools and fabrication machines

Soldering iron (generic)

Story

Introduction

Most benchtop/lab power supplies use rotary encoders and push buttons for its user interface. I wanted to replace all those mechanical inputs with Infineon CapSense based touch interface. This makes the power supply liquid splash proof, dust resistant and sleek looking. It is also portable and can be powered from lipo battery pack.

Features

5 Button HMI for voltage, current limit, output adjustment
Input/output voltage and load current monitor OLED display
Current limiting trip feature for safety with latch relay
One tap output voltage enable/disable
Voltage adjustment control with digital potentiometer
Current measurement with hall effect sensor
Working input voltage range 7-35 VDC from adapter/battery/solar
Voltage stepping of 40mV

Video Demo

Touch based HMI for portable power supply

Device Operation

At the heart of this device is PSoC4 CY8C4245-483 ARM Cortex M0 microcontroller, which is performing following operations :

CapSensing for user Input

There are 5 CapSense touch button for user inputs to increase/decrease output voltage, set trip current limit, enabling/disabling output. These buttons work both in touch/tap and continuous touch/hold mode. Buttons are activates when the plastic overlay top of them are touched.

OLED Display

This 1306 I2C 128x32 pixel display will show output voltage, trip current, approximate load current information.

Measuring Voltage and Current

Output voltage is measured with resistive voltage divider and load current is measured with ACS 712 5A hall effect sensor which converts current info into analog voltage. Then PSoC internal 12 bit ADC is used to convert those analog voltage, with come calculations actual voltage and current information is retrieved.

Adjusting Output Voltage

The output voltage is adjusted according to the touch inputs from user, by sending increment/decrement command to a digital potentiometer chip over SPI interface.

This eliminates any mechanical/moving parts from the device making it more reliable for long term operation.

Output Drive and Over current Protection

Output voltage is enabled/disabled through a latching relay. Based

PSoC Configuration

Pin Mapping

mcu pin mapping

CySch Setup

CapSense component configuration

ADC Configuration

SPI Configuration

Programming

I have used the following technique to program the PSoC 4 chip wirelessly :

PSoC 4 Wireless Programming (my other tutorial on PSoC 4 programming)

Potential Applications

Touch based DC Power-tools Speed Controller
Touch controlled Adjustable Power Supply
Step Voltage LED Brightness Control with Touch based HMI
Testing electronics IC and components voltage range

Conclusion

This demo shows how capsense can replace mechanical knobs and switches from Lab/Benchtop power supplies than many universities/engineering farms use. The prototype I made here is not complete, the voltage range is limited, output is not continuous analog, current measurement is not accurate. More work needs to be done to turn this into a commercial solution to replace existing power supplies on the market. This idea just demonstrates the beginning of it

References

Code

// Copypaste by Who ? lol, that's me !

#include <project.h>
#include <stdlib.h>
#include <stdio.h>
#include "ssd1306.h"

#define DISPLAY_ADDRESS 0x3C // I2C Oled address 0x3C

//#define R_Lower         10   // 10k Resistor for voltage divider   
//#define R_Upper         100  // 100k Resistor for voltage divider
//#define V_Ref           5    // 5V as ADC reference (0V to 5V range
//#define ADC_Resolution  4096 // 12 bit ADC
//#define Current_Scaling 185  // ACS712 output changes by 185mV/A 

// some variables to measure and calculate ADC results
uint16_t I_Sense = 0;
uint16_t V_Sense = 0;
int Volts = 0;
int Amps = 0;
int Current_Limit = 300;
char Results[10];
uint8 output = 0;
// mcp4131 10k SPI digipot resistance changing commands
uint8_t increment_cmd = 0b00000100;
uint8_t decrement_cmd = 0b00001000;

void refresh_oled(void) 
{
    CyDelay(100); 
    display_clear();
}

void enable_outout (void)
{
    Load_Off_Write(0);
    Load_On_Write(1);
    Output_OnOff_LED_Write(1);
    output = 1;
    CyDelay(75);
    Load_On_Write(0);
    
}


void disable_outout (void)
{
    Load_On_Write(0);
    Load_Off_Write(1);    
    Output_OnOff_LED_Write(0);
    output = 0;
    CyDelay(75);
    Load_Off_Write(0);
    
}

void haptic_feedback (void)
{
    HapticVibe_Write(1);
    CyDelay(40);
    HapticVibe_Write(0);
}
/// beginning of main ///

int main(){
    // this variable will keep track of  
    // latest touch infut from user
    uint16 which_button = 999;
    
    // making sure output is disabled at startup
    disable_outout();
    //Init Global Interrupt
    CyGlobalIntEnable;
    
    
    // Init CapSense for Touch HMI
    CapSense_Start();
    CapSense_InitializeAllBaselines();
 //   CyDelay(50);
    
    // Init ADC for voltage, current, power measurement
    ADC_IV_Sense_Start();
 //   CyDelay(50);
    
    // Init SPI to control 10k MPC4131 digital pot
    SPI_Digipot_Start();
 //   CyDelay(50);
    
    // config 1306 OLED // text settings, font size
       // Init 1306 I2C OLED
    I2COLED_Start();
 //   CyDelay(50);
    display_init(DISPLAY_ADDRESS);
    display_clear();    
    display_update();      
    gfx_setTextSize(3);
    gfx_setTextColor(WHITE);
    gfx_setCursor(0,0);
  
    /// for forever ///
    
        for(;;){

        // if someting is sensed by capsense module
        // (i.e. any touch from user) process it  
        // this is the core HMI function of this device
            
        while ( CapSense_IsBusy() !=0 )
        {}
            CapSense_ProcessAllWidgets();
            
                if( CapSense_IsWidgetActive(CapSense_BUTTON0_WDGT_ID)) 
           
            {
             which_button = 0;
            }
            
            else if( CapSense_IsWidgetActive(CapSense_BUTTON1_WDGT_ID))
            {
             which_button = 1;
            }
            
             else if( CapSense_IsWidgetActive(CapSense_BUTTON2_WDGT_ID))
            {
                which_button = 2;
            }
            
             else if( CapSense_IsWidgetActive(CapSense_BUTTON3_WDGT_ID))
            {
                which_button = 3;
            }
            
             else if( CapSense_IsWidgetActive(CapSense_BUTTON4_WDGT_ID))
            {
                which_button = 4;
            }
            // trigger under overload or short circuit condition
             else if( Amps > Current_Limit)
            {
                which_button = 1;
            }
            else
            {
             which_button = 999;
            }
            
            ////////////////////////////////////////////////
            // Get ADC to measure current & output voltage//
            ////////////////////////////////////////////////
            for(int i=0; i<8; i++)
            {
            ADC_IV_Sense_StartConvert();
            while(ADC_IV_Sense_IsEndConversion(ADC_IV_Sense_RETURN_STATUS))
            {} // blocking while polling/scanning ADC
            
            // Get raw counts from ADC ch 0 an ch 1
            I_Sense =I_Sense + ADC_IV_Sense_GetResult16(0);
            V_Sense =V_Sense + ADC_IV_Sense_GetResult16(1);
            }
            I_Sense = I_Sense/8;// avg of 8 readings
            V_Sense = V_Sense/8;// avg of 8 readings
            // convert into real voltage and current data
            //float Voltage = (V_Sense/4096.0)*5.0*(10+1)/10.0;
            // float Voltage = V_Sense*0.001343;
            // float Amperage  = 1000/(5000/4096*185);
            Volts = (V_Sense*1.343) ; // convert into mV
            Amps  = ((I_Sense-2048)*4.4247) ;   // convert into mA
            // ADC_IV_Sense_StopConvert();
            I_Sense = 0;
            V_Sense = 0;
    
            
            /////////////////////////////////////////////
            /////////////////////////////////////////////
            // HMI Action based on user input on touch //
            /////////////////////////////////////////////
            /////////////////////////////////////////////
            
            if (which_button == 0)
            {
             // adjust digital pot to decrease output voltage
             SPI_Digipot_WriteTxData (increment_cmd);
             
             gfx_setCursor(0,0);
             gfx_print("volt(-)");
             gfx_setCursor(0,32);
             gfx_print(itoa(Volts,Results,10));
             gfx_setCursor(85,32);
             gfx_print("mV"); 
             display_update();          
             haptic_feedback();
             refresh_oled();
             
            }
            
            if (which_button == 1)
            {
               // Disconnect output latch relay to 
               // disable output voltage
               // can be user trigger or overload triggered
               gfx_setCursor(0,0);
               haptic_feedback();
               disable_outout();
            
               // display info on Oled display
               gfx_print("Pwr OFF");
               display_update();
               refresh_oled();
                          
            }
            
            if (which_button == 2)
            {
               gfx_setCursor(0,0);
               haptic_feedback();
               // display info on Oled display
               gfx_print("Current");
               gfx_setCursor(0,32);
               gfx_print(" Limit ");
               display_update();
               refresh_oled(); 
               Current_Limit = Current_Limit+100;
               if (Current_Limit>3000)
               {Current_Limit = 300;}
               gfx_setCursor(0,0);
               gfx_print(itoa(Current_Limit,Results,10));
               gfx_setCursor(85,0);
               gfx_print("mA");
               display_update();
               refresh_oled(); 
            
            }
            
            if (which_button == 3)
            {
               // Connect output latch relay to 
               // enable output voltage 
                haptic_feedback();
                enable_outout();
            // display info on Oled display
               gfx_setCursor(0,0);
               gfx_print("Pwr ON");
               display_update();
               refresh_oled();
            }
            
            if (which_button == 4)
            {
             // adjust digital pot to increase output voltage
               SPI_Digipot_WriteTxData (decrement_cmd);
               
               
             gfx_setCursor(0,0);
             gfx_print("volt(+)");
             gfx_setCursor(0,32);
             gfx_print(itoa(Volts,Results,10));
             gfx_setCursor(85,32);
             gfx_print("mV"); 
             display_update();          
             haptic_feedback();
             refresh_oled();
             
            }
            
            
            // when no touch detected //
            if (which_button ==999)
            {            
            // disable vibration + visual feedback    
            HapticVibe_Write(0);
            
            
            if (!output)
            {Volts = 0; Amps = 0;}
            
            // show output current on display
            gfx_setCursor(0,0);
            gfx_print(itoa(Amps,Results,10));
            gfx_setCursor(85,0);
            gfx_print("mA");
            
            // show output voltage on display
            gfx_setCursor(0,32);
            gfx_print(itoa(Volts,Results,10));
            gfx_setCursor(85,32);
            gfx_print("mV");
           
            display_update();
            refresh_oled();
            
            }
            
        // scan again to check any CapSense input 
        // given bu the user or not    
        CapSense_ScanAllWidgets();
        // CapSense_UpdateEnabledBaselines();    
    }    ///// end of forever /////
} ///// end of main /////
///////////////////////////////////////////////////////
///////////////////////////////////////////////////////
///////////////////////////////////////////////////////

Credits

Shahariar

74 projects • 266 followers

"What Kills a 'Great life' is a 'Good Life', which is Living a Life Inside While Loop"

PSoC4: CapSense based Portable Power Supply