Tag: awesome

  • INA219 Current Sensor and MicroPython

    More Micropython programmers — and especially beginners — should know about Awesome MicroPython. It’s a community-curated list of remarkably decent MicroPython libraries, frameworks, software and resources. If you need to interface to a sensor, look there first.

    For example, take the INA219 High Side DC Current Sensor. It’s an I²C sensor able to measure up to 26 V, ±3.2 A. It does this by measuring the voltage across a 0.1 ohm precision shunt resistor with its built-in 12-bit ADC. I got a customer return from the store that was cosmetically damaged but still usable, so I thought I’d try it with the simplest module I could find in Awesome MicroPython and see how well it worked.

    I guess I needed a test circuit too. Using all of what was immediately handy — a resistor I found on the bench and measured at 150.2 ohm — I came up with this barely useful circuit:

    simple circle with 3.3 V DC supply ad two resistors of 150.2 ohms and 0.1 ohms in series
    Should indicate a current of 3.3 / (150.2 + 0.1) = 21.96 mA

    The INA219 would be happier with a much higher current to measure, but I didn’t have anything handy that could do that.

    Looking in Awesome MicroPython’s Current section, I found robert-hh/INA219: INA219 Micropython driver. It doesn’t have much (okay, any) documentation, but it’s a very small module and the code is easy enough to follow. I put the ina219.py module file into the /lib folder of a WeAct Studio RP2040 board, and wrote the following code:

    # INA219 demo - uses https://github.com/robert-hh/INA219
    
    from machine import Pin, I2C
    import ina219
    
    i = I2C(0, scl=Pin(5), sda=Pin(4))
    print("I2C Bus Scan: ", i.scan(), "\n")
    
    sensor = ina219.INA219(i)
    sensor.set_calibration_16V_400mA()
    
    # my test circuit is 3V3 supply through 150.2 ohm resistor
    r_1 = 150.2
    r_s = 0.1  # shunt resistor on INA219 board
    
    # current is returned in milliamps
    print("Current       / mA: %8.3f" % (sensor.current))
    # shunt_voltage is returned in volts
    print("Shunt voltage / mV: %8.3f" % (sensor.shunt_voltage * 1000))
    # estimate supply voltage from known resistance * sensed current
    print("3V3 (sensed)  / mV: %8.3f" % ((r_1 + r_s) * sensor.current))
    
    

    with everything wired up like this (Blue = SDA, Yellow = SCL):

    breadboard with RP2040 pico board and INA219 sensor board benath it, and the 150 ohm wired as a circuit on the side
    all of the wires

    Running it produced this:

    I2C Bus Scan:  [64] 
    
    Current       / mA:   22.100
    Shunt voltage / mV:    2.210
    3V3 (sensed)  / mV: 3321.630
    

    So it’s showing just over 22 mA: pretty close to what I calculated!

  • just look at this moose stamp

    Just look at it:

    No, really look at it:

    I DON’T THINK YOU’RE LOOKING AT IT PROPERLY …


  • Wild East is cool

    I just sold a bunch of CDs to Wild East on the Danforth. I got a pretty good deal on them. This is what I bought with part of the proceeds:

    • Anne LeBaron / Rana, Ritual & Revelations
    • Badly Drawn Boy / One Plus One Is One
    • Devendra Banhart / Nino Rojo
    • Elliott Smith / From A Basement On The Hill
    • Kate Rusby / Underneath The Stars
    • Sterling Roswell / The Psychedelic Ubik