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Discrete Analogue to Digital converter

Knighthawk_140

Hello.

I have made a 14bit single slope adc

  • in reply to dang74

    Go for it.

    Think of it like a CR timer, C x R = T (time to charge) but instaid of a curved ramp you get a Linear ramp because I = is a constant current.

    where R = V/I

    then you have C x R = Time.

    Sorry i can't give values but thats my secret sauce, being one of the very few to pull off a home built 14bit adc.

    if you have a signal generator, then use that to enable / disable the ramp at the input to R2 in my sketch. or just pull low to start ramp and pull high 5V to stop ramp. 

  • in reply to Knighthawk_140
    Knighthawk_140 said:
    Sorry i can't give values but thats my secret sauce, being one of the very few to pull off a home built 14bit adc.

    That's the part I don't get. Why post an experiment on a public forum, and then not share part of it "because secret". it's an ADC. What's the value of keeping this secret?

  • in reply to Jan Cumps

    Hello,

    This took me 10 days to figure this out, so I give a 10 day challenge to evey one.

    I have just one more thing to see if I can make this rock solid

  • in reply to Knighthawk_140

    A challenge would need a more detailed spec:

    • Integral non linearity
    • Differential non linearity
    • Noise
    • Temperature drift
    • Sampling rate
    • Gain error/drift
    • Offset
    • Calibration interval

    It's quite acceptable for any of these parameters to be unspecified but if you don't pin down some of them it's not much of a challenge.

    For example - in your design schematic the current source is unlikely to be very linear (see TI document SYLT768.pdf).

    Too busy right now to have a go but if I do I'll tell you when my 10 days start Slight smile

    MK

  • in reply to michaelkellett

    This was just a diy build in my flat at weekends and evenings, I don't have an environmental chamber in my front room, i was seeing if it was possible to get a 14bit adc stable and fairly linear. If you analyse my video below you will see what I have achieved 

  • in reply to Knighthawk_140

    Good Morning on this lovely Sunday, here is my ADC ramp in glorious 4K

  • A little bit better stability with my Single Slope ADC. I was bored.

  • I am approaching 16bit Territory, with approximately 15.8bit ADC count, with stability to now see 1mV increments and decrements, amazing what you can do when your bored at home.

    Here is a little video of my progression.