After obtaining a lot of Chinese 18650 batteries labeled "5000 mAh" I decided to find out just how much capacity they DO have.
This tester features an Ardunio Nano, a Nokia 5110 display, a rotary encoder for operation, and a FET current source using a high -power mosFET (IRLZ44).
The schematic:
The current source consists of the IRLZ44 mosFET, and the 10 turn pot which can be any value between 50K and 500K. I used a 500K I had lying around. The FET acts as a variable power resistor to load the test battery.
My Nokia display was a 5 volt version... be sure to check which version you have and power it accordingly... many out there are 3v3 versions.
I tried many different encoder libraries with somewhat dismal success until I found SimonM83 excellent Instructables article. That code is awesome its very 'light' (no libraries and interrupt driven) and is used in this sketch. Thanks Instructables and SimonM83!
Using the Vin on the Nano to power insures accurate ADC measurements since the reference used is the 5 volt rail. Using the USB to power will cause inaccuracies unless you compensate in the sketch.
float mAh = 0.0;
float senseR = 1.0; // In Ohms - Shunt resistor resistance
float voltRef = 5.00; // Reference voltage for ADCs
float current = 0.0;
float battV = 0.0;
float senseV = 0.0;
float battLow = 3;
unsigned long previousMillis = 0;
unsigned long millisPassed = 0;
//Encoder variables
volatile byte aFlag = 0; // let's us know when we're expecting a rising edge on pinA to signal that the encoder has arrived at a detent
volatile byte bFlag = 0; // let's us know when we're expecting a rising edge on pinB to signal that the encoder has arrived at a detent (opposite direction to when aFlag is set)
int encoderPos = 0; //this variable stores our current value of encoder position.
int oldEncPos = 0; //stores the last encoder position value
volatile byte reading = 0; //somewhere to store the direct values we read from our interrupt pins before checking to see if we have moved a whole detent
void setup() {
pinMode(pinA, INPUT_PULLUP); // set pinA as an input, pulled HIGH to the logic voltage (5V or 3.3V for most cases)
pinMode(pinB, INPUT_PULLUP); // set pinB as an input, pulled HIGH to the logic voltage (5V or 3.3V for most cases)
attachInterrupt(0,PinA,RISING); // set an interrupt on PinA, looking for a rising edge signal and executing the "PinA" Interrupt Service Routine (below)
attachInterrupt(1,PinB,RISING); // set an interrupt on PinB, looking for a rising edge signal and executing the "PinB" Interrupt Service Routine (below)
pinMode(pinC,INPUT);
display.begin();
display.clearDisplay(); // clears the screen and buffer
display.display();// Update display
display.setContrast(50);
display.clearDisplay();
display.println("BattCapacity");
display.println("v2.0");
display.println("");
display.print("Tim Stoddard");
// display.drawRect(0, 0, 84, 48, BLACK);// start x,y then width,height
// display.fillRect(0, 30, 16, 4, BLACK);
display.display();
while (digitalRead(pinC)){continue;}// wait for press and release of switch
while (!digitalRead(pinC)){continue;}
}
void PinA(){
cli(); //stop interrupts happening before we read pin values
reading = PIND & 0xC; // read all eight pin values then strip away all but pinA and pinB's values
if(reading == B00001100 && aFlag) { //check that we have both pins at detent (HIGH) and that we are expecting detent on this pin's rising edge
encoderPos --; //decrement the encoder's position count
bFlag = 0; //reset flags for the next turn
aFlag = 0; //reset flags for the next turn
}
else if (reading == B00000100) bFlag = 1; //signal that we're expecting pinB to signal the transition to detent from free rotation
sei(); //restart interrupts
}
void PinB(){
cli(); //stop interrupts happening before we read pin values
reading = PIND & 0xC; //read all eight pin values then strip away all but pinA and pinB's values
if (reading == B00001100 && bFlag) { //check that we have both pins at detent (HIGH) and that we are expecting detent on this pin's rising edge
encoderPos ++; //increment the encoder's position count
bFlag = 0; //reset flags for the next turn
aFlag = 0; //reset flags for the next turn
}
else if (reading == B00001000) aFlag = 1; //signal that we're expecting pinA to signal the transition to detent from free rotation
sei(); //restart interrupts
}
I was excited when I saw that Adafruit got the VL53LOX LIDAR range sensor back in stock and immediately ordered 5 of them. I just received them and already they are sold out again. I can see why! This is a highly accurate range sensor using a laser to measure time-of-flight.
The sensor is very easy to install and set up. I did have issues using the Adafruit libraries so I used the Pololu libraries from GitHub. This library worked perfectly. Just hook up power (5 or 3.3) to the sensor and then the I2C connections (SCL and SDA) to your Arduino. There is example software in the Pololu library, just install that library into your Arduino IDE and select from examples.
I was looking to add some NEOs to another project and wanted to see if a PIC could be programmed to drive them. Thus the birth of this POC. I took some inspiration from an Adafruit tutorial on writing your own driver for a PIC. This tutorial focused on the RGB version of the NEO (no separate white LED) The PIC used was a PIC 18F4550 clocked at 48Mhz in order to be fast enough for the timing. It's not quite fast enough to technically keep within the specs for the NEOs but it was learned in this tutorial that only the positive pulse width is relevant (within reason) and the author was able to keep that within the variance spec.
This experiment is to see if I can do the same for a much smaller PIC: 12F1840 driven at it's max clock rate of 32Mhz and using the RGBW version of the NEO: An Adafruit NEOPixel stick (8 NEOs with RGBW LEDs). I was able to do it as can be seen in the video:
The PIC is configured to use internal PLL for generating an internal 32 Mhz clock which, with a few coding optimizations is just fast enough to get within specs of the NEOs for that critical positive pulse width. In addition I coded this to use 32 bit format for the RGBW version of the NEO.
So now I can use this same technique to incorporate NEOs into a much smaller (8 pin device) PIC.
The schematic for this POC:
The entire project was coded in XC8 (free version) with one function using in-line assembler to get the speed needed to meet timing requirements for the NEOs. The zipped MPLABX project package is here.
An automated work desk light, AC control, and assistant...
This project came to life when I started wondering if I had left the work desk light on? Is the soldering iron still on? I needed some automation at my desk to reliably determine when I'm at my desk and do a few things:
Switch on the strip light when I sit down.
Give me the ability to turn on the bright LED desk light
Ability to DIM all lighting
Give me the ability to turn on the desk AC (soldering iron, etc)
Ability to use a single touch switch for all activity
Know when I LEAVE the desk and turn off everything.
Give Basic desk temp/humidity
Be expandable for future additions of sensors and probes to assist with development
With the proliferation of inexpensive Arduino clones, I decided to use a $4 Arduino Nano clone available on Amazon for $4... amazing! I used readily available parts and modules from Adafruit ST7735 Display, and the Range Sensor. The MosFETs from Mouser, the LED strip from Amazon. The touch sensor I got from a sensor kit on Amazon, but you could also just use a standard push button. The potentiometer can be pretty much any value from 1k to 100k... I used a 10k slider I had laying around. The 10w LED I got from Electronic Goldmine. Finally, the Powerswitch Tail is the safest way to switch the AC mains!
The MosFETs are SMD but can be easily soldered to a three pin header for breadboarding... these FETs have a very low (2v) gate voltage along with a very low on resistance of about 200 mOhms enabling these to switch high currents without much dissipation.
The 10 watt LED should be attached to a heat sink... I used a CPU cooler heat sink readily available and then just attached the LED to it using heat-sink tape.
Once you assemble the circuit, load this sketch and have fun! I look to enhance this as I use it and will update this when that happens.
/*
* Workdesk Assistant
* Tim Stoddard
* Released to public domain with this credit given
* Press switch:
* short < 1 sec to toggle between 'panels'
* medium 2 sec to light 10w LED on panel 1 only
* long 3 sec to turn on AC on panel 1 only
* really long 4 sec unused
*
* Note you can define different uses of the presses on each 'panel'
* You can code any number of 'panels' ... don't forget to code the activities for that panel
This is an experiment to illustrate control element dissipation with the use of a PIC 12F1840 operating as a touch switch and PWM to drive a 12v 10 watt LED using a single MosFET (BSS806N) as the driver.
My wife wanted a simple touch switch battery powered sconce light... sounded like a great fit for a PIC 12F1840... small 8 pin microcontroller with a built in CSM (Cap Sense Module) also sometimes referred to as a CPS module. Attempting to research this was incredibly frustrating! There is just no SIMPLE example out there in either assembler or C! Everywhere I looked was only examples of using the mTouch library, which although a nice library is just far too much over-kill for my needs. Other research from forums suggested that the peripheral is just too complex and tweeky to be of much use. So off on my own... I dug into the manuals and put this simple example of using the CSM module on a PIC12F1840 (and probably the 12F1822 as well) written in XC8 free edition. Here it is in operation.
The PIC12F1840 CSM module is simply an R/C oscillator feeding a frequency counter! You select one of the four available pins as the capacitor input pin for the oscillator, setup timer 0 as the frequency counter time base, and timer 1 as the counter to count the R/C oscillator. The time base (Timer 0) is set to interrupt the PIC at specific intervals and it also gates the R/C pulses going to Timer 1. That interval should be long enough to capture a large count in Timer 1 from the R/C oscillator. The system clock is configured for internal 4MHz and Timer 0 is configured for a prescaling of 256. This gives a count of around 33,000 in Timer 1 (16 bit counter) or about half way through. So for every time interval of Timer 0 interrupting the PIC, Timer 1 will have a count of about 33,000 in it. Now in the interrupt routine you just read Timer 1 into a global variable, reset Timer 1 to zero, and re-enable interrupts for the next read. In the main body of code you just loop and watch the Timer 1 value stored in the global variable (touch in my case) and act on that value when it changes. Simple! If there is any change in the R/C oscillator's cap sense pin (like a finger, or other larger object), that will change the capacitance on that pin and shift the oscillator down ... Timer 1 will reflect that with a smaller count. Now just have your code watch for the change to a smaller count and you have a touch switch. Here are the XC8 files out of the MPLABX IDE:
/***********************************/
/* Simple PIC 12F1840 Touch Switch Example */
/* main.c - Tim Stoddard, 2016 */
/***********************************/
#include <xc.h> /* XC8 General Include File */
#include <stdint.h> /* For uint8_t definition */
#include <stdbool.h> /* For true/false definition */
#include "system.h" /* System funct/params, like osc/peripheral config */
#include "user.h" /* User funct/params, such as InitApp */
/***********************************/
/* User Global Variable Declaration */
/***********************************/
/* i.e. uint8_t <variable_name>; */
/***********************************/
/* Main Program */
/***********************************/
void main(void)
{
/* Configure the oscillator for the device */
ConfigureOscillator();
/* Initialize I/O and Peripherals for application */
InitApp();
/* Flash the LAMP a few times */
for(i=0;i<5;i++){
LAMP=1;
__delay_ms(50);
LAMP=0;
__delay_ms(200);
}
/* grab the latest count from Timer 1 (touch), subtract a threshold amount,
and save it (touch_cal) */
touch_cal=touch-1000;
/* MAIN LOOP */
while(1)
{
if(touch<touch_cal){// sensor is touched
LAMP=1;// turn it on
}else{// otherwise ...
LAMP=0;// turn it off
}
}
#include <xc.h> /* XC8 General Include File */
#include <stdint.h> /* For uint8_t definition */
#include <stdbool.h> /* For true/false definition */
#include "user.h"
/***********************************/
/* User Functions */
/***********************************/
void InitApp(void)
{
/* Setup analog functionality and port direction */
TRISA = 0b00111011; // RA2 is output
ANSA4=1;
/* Initialize peripherals */
CM1CON1=0;
CPSCON0bits.CPSRM=0;// 1=variable voltage ref, 0=fixed
CPSCON0bits.CPSRNG=0b11;// high current
CPSCON0bits.CPSON=1;
CPSCON1bits.CPSCH=0b11;//CPS3 selected
//Timer 0 is the time base for CPS
TMR0CS=0;//Timer 0 used as time base for CPS select Fosc/4
OPTION_REGbits.PS=0b111;
OPTION_REGbits.PSA=0;
// Timer 1 is the freq counter for CPS
T1CON=0b11000101; // TMR1 capacitive sensing osc, prescaler 1/1, dedicated osc disabled,no synch,timer1 enabled
T1GSEL=0b01;// set timer 1 gate for TMR0 overflow
/* Enable interrupts */
TMR0IE=1;// enable TMR0 interrupts
PEIE=1;//enable Peripheral interrupts
GIE=1;// enable global interrupts
}
