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| iMo:
I've been using the ADS1110, diff input, i2c, 6 pins sot32, 15+ meas/sec, 16bit, 2.048V 5ppm/C internal Vref, 1-8x PGA, mind they have got several hardwired i2c addresses, so do select different part numbers when hanging them several on a single i2c bus. |
| macboy:
Any microcontroller with a decent 12+ bit ADC can easily implement a voltmeter suitable for a bench supply type of application. Take a bunch of samples and average them (reducing noise and maybe increasing resolution by dithering), do offset and gain calculations, and display the result on the display device of your choice, anything from some multiplexed 7-seg LEDs, to a fancy color LCD or OLED depending on what cost and effort you want to invest. The ICL7106 type devices are generally set up to sample 2 to 3 times per second. I find that to be way too slow for a bench supply. By tweaking a few components, you can easily get 10+ samples per second for a much faster reacting display, which makes adjusting a supply much easier. You need to change the RC oscillator (reduce RC time constant) but also potentially reduce the integrating capacitor to prevent loss of accuracy (smaller integration time means you probably want a small capacitor, read the datasheet application notes). I have some commercially built supplies with these devices, and I always do these tweaks to improve usability. |
| tooki:
Take a look at https://www.eevblog.com/forum/projects/ode-to-the-ina226-voltagecurrent-sensor/ In it, I discuss its use for precisely this use case: a responsive panel meter for a lab PSU. I think it’s an excellent, inexpensive solution that’s also incredibly flexible. |
| snoozer:
Hi, I have been playing around for a while now with the ADS1115, both single ended and differential. The resolution is definitely not a concern at all and single ended it works quiet well on the breadboard. When I set it up as differential input I do have a lot of noise. A lot of the noise comes from the USB connection through the MC that I use. If I power the circuit from a linear PSU its a lot better but still not really usable. I have to dig a bit deeper and check how I need to filter the input for the ADC to get rid of as much noise as possible. I will be using the STM32F103C.... "Blackpill" which works with the Arduino bootloader and has a working USB-port unlike the "Bluepull". The Arduino Nano does not give me the smooth readout on the OLED I am using and at the same time do temperature control for a fan and also temp readout, its just to slow. I have 2 other MCs ordered, the ordinary Arduino Mega 2..something and a Arduino Due which is a 32bit MC as well apparently. Have not received them yet so no clue about them so far. So what I am looking into now is the filtering of the ADC input and also how I can isolate the entire ADS1115 from the MC (I2C over optocoupler). In the end "Product" the digital circuits will have an independent PSU from a separate transformer winding or a 2nd transformer with a fixed voltage regulator either 5V or 3.3V depending on the MC I end up using. Also I decided I go with a 10mV resolution on the voltage readout, I have not yet even looked into the current side of things yet. Regards Jan |
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