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Discrete Analogue to Digital converter

Knighthawk_140

Hello.

I have made a 14bit single slope adc

  • That sounds cool. Can you post a picture of it or a schematic or do you have a question about it?

  • in reply to dougw

    I have a video up on youtube of this working, it is based on a ramp counter, constant current linear ramp with comparator. I used an STC89C52 running at 20Mhz in 6T mode, this is based on the old 8051 microcontroller. With 20x4 LCD

  • Very cool!  Welcome to the element13 community and thanks for sharing you work!

  • in reply to genebren

    Thanks, Here it is working., I'm measuring my power supply with my DVM as a reference

  • in reply to Knighthawk_140

    We need a schematic - it's like home work - you only get marks if we can see your workings out  Relaxed

    For an A++ grade - try making it logarithmic !

    MK

  • in reply to michaelkellett

    Why would I want to convert a linear voltage scale to logarithmic 

  • in reply to Knighthawk_140

    A long time ago when an 8 bit monolithic ADC was expensive and the best you could buy was 12 bit, I had to design an auto ranging audio frequency level meter for BT. We wanted to be able to cover 14dB in each range with a worst case accuracy of 0.1dB which needs at least 10 bit resolution if you use a linear ADC. But if you use  a logarithmic ADC you only need 140 divisions rather than 1024. A single slope log converter can be made by replacing the current source with a resistor. Two comparators rather than 1 enables you to auto-cal it on every conversion. But you needed a decent capacitor - think we used a 10nF polystyrene one.

    But now you can buy an I2C interfaced 16 bit converter with two differential input ports, one with very low offset for under £1 (an INA230) so the art of single, dual and even multi-slope converters has had its day Slight frown

    MK

  • in reply to michaelkellett

    Nice, mine is a linear dc voltage display with raw A to D count of 19716 counts at 9V input to give me mV resolution, gives me just over 14bit resolution, no software filtering and no software linearity correction, pure raw Analogue linearity.