Analog Input in realtime
- rajsekhar
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05 Aug 2022 15:51 #249126
by rajsekhar
Analog Input in realtime was created by rajsekhar
Dear Friends..
I want to know the ways to have a sensor analog output to be read into linuxcnc in realtime.
The application I am looking for is adaptive feed control in lathe/mill via power (current sensor) measurement.
Earlier, I have sucessfully taken integer input from arduino (usb connected) into hal (via python). But that I think was not in realtime.
How realtime float input is possible??
I want to know the ways to have a sensor analog output to be read into linuxcnc in realtime.
The application I am looking for is adaptive feed control in lathe/mill via power (current sensor) measurement.
Earlier, I have sucessfully taken integer input from arduino (usb connected) into hal (via python). But that I think was not in realtime.
How realtime float input is possible??
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- Henk
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05 Aug 2022 16:47 #249131
by Henk
Replied by Henk on topic Analog Input in realtime
Best sollution is probably one of Mesa's THCAD cards. It is basically an A/D converter that outputs a signal that can be counted with one of the encoder inputs
There is a 10v and a 300v version
There is a 10v and a 300v version
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- PCW
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05 Aug 2022 16:55 #249132
by PCW
Replied by PCW on topic Analog Input in realtime
A 7I87 is another possibility if you need multiple channels
Also there is a crude (8bit) 4 channel analog input capability on many Mesa daughtercards
(7I73,7I76,7I77,7I84)
Also there is a crude (8bit) 4 channel analog input capability on many Mesa daughtercards
(7I73,7I76,7I77,7I84)
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- tommylight
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05 Aug 2022 17:17 #249136
by tommylight
Replied by tommylight on topic Analog Input in realtime
Or write a driver for using analog Line Inputs on the motherboard, 2 inputs at high resolution, but also high sensitivity (usually 1VPP).
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- andypugh
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05 Aug 2022 22:25 #249165
by andypugh
Replied by andypugh on topic Analog Input in realtime
Or: Use a PWM output into a filter, and a (physical) comparator to feed back if your pwm is higher or lower than the measured voltage, then a PID loop in HAL trying to achieve a value of 0.5 in the feedback will track the external voltage.
Probably.
I have never actually tried this, but its basically a crude "tracking ADC" implemented in HAL. It will cost you two IO pins, though.
You could also bitbang an I2C ADC: www.ebay.co.uk/itm/195025832761 or similar, but that might not be fast enough (it will take 32mS to bitbang a 16 bit value out of it)
If you are using a Mesa card, then there is an SPI module in the firmware, and then an external ADC could be sampled at 1kHz.
Probably.
I have never actually tried this, but its basically a crude "tracking ADC" implemented in HAL. It will cost you two IO pins, though.
You could also bitbang an I2C ADC: www.ebay.co.uk/itm/195025832761 or similar, but that might not be fast enough (it will take 32mS to bitbang a 16 bit value out of it)
If you are using a Mesa card, then there is an SPI module in the firmware, and then an external ADC could be sampled at 1kHz.
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