wildbill:
Why complicate things with a Pi? There are plenty of LCDs you can drive from an Arduino.
But we need to save the values also. Need to store the data continuously for hours. The Arduino does not have such storage capabilities. Interfacing with Pi and storing the data in Pi was suggested. And we could also use Pi to drive the LCD display.
Your suggestions are most welcome.
rosh_kazhak62:
Typically, we measure within 0-5V, but the max voltage I would be measuring will be 10.6V and the half of it comes to 5.3V exceeding the limit. Is there any way to overcome it.
Of course. Use a different set of resistors for your voltage divider, so your 10.6V goes to ~4.5V (this to leave some safety margin). E.g. 33k and 24k to bring 10.6V down to 4.463V. Or 10k and 7k5 to get 4.543V. This are all standard E24 values. Look what you have in your box of resistors that gets the correct ratio, and a total input impedance of about 10k, not too much more, to keep the analog input happy.
What was wrong with using a 1k:10k or 10k:100k divider and 1.1volt Aref.
Using that results in a more stable readout and higher protection.
Send the raw A/D values (int) to the Pi to store.
Then calculate voltage from that on the Pi.
Leo..
Wawa:
What was wrong with using a 1k:10k or 10k:100k divider and 1.1volt Aref.
Using that results in a more stable readout and higher protection.Send the raw A/D values (int) to the Pi to store.
Then calculate voltage from that on the Pi.
Leo..
Thanks for the suggestions. Is the communication between Arduino and Pi be made using the Serial.begin(9600) code?
wvmarle:
Of course. Use a different set of resistors for your voltage divider, so your 10.6V goes to ~4.5V (this to leave some safety margin). E.g. 33k and 24k to bring 10.6V down to 4.463V. Or 10k and 7k5 to get 4.543V. This are all standard E24 values. Look what you have in your box of resistors that gets the correct ratio, and a total input impedance of about 10k, not too much more, to keep the analog input happy.
This too is a nice idea. If we are to use the 33k, 24k combination, that means the input impedance seen by the Arduino would be more than 10k and that is not desirable.
It'd come to about 14k which is no problem at all.
As long as you're well under 100kΩ you'll be fine, except for really fast changing signals.
Indeed the 10k+100k option is a very good one as well.
wvmarle:
It'd come to about 14k which is no problem at all.
As long as you're well under 100kΩ you'll be fine, except for really fast changing signals.Indeed the 10k+100k option is a very good one as well.
Things keep coming up. I want a 10k sampling rate for my data collection towards the end of the data collection. The initial sampling rate could be arbitrary, but towards the end, a 10k or better sampling rate is required.
Any suggestions?
External ADC as the Arduino's ADC can do no more than about 9.6k sps.
Well, there are ways to increase that pretty drastically by fiddling with the registers but you lose accuracy.
Would it be possible to send both the voltage data value and the time at which this voltage was collected from the Arduino to the Pi?
I would need the time duration in minutes, as the data recording could go on for hours. Also, towards the end of data recording, Arduino has to collect the data every 2 minutes and display it using the monitor.
Of course, sounds perfectly possible.
Sorry, lost track of the requirements.
Measure a voltage with the Arduino, display it on an LCD, and then log it, with time.
An common Arduino can't log, and hasn't got a clock.
So why use an Arduino if you're going to send everything to a Pi.
Anything else this setup has to do?
Leo..
There's a Pi in the mix that for sure can give the current time to the Arduino every hour or so. Internal timekeeping isn't that bad.
I also lost track of what OP really wants to do but don't see anything obviously out of what an Arduino can do.
Wawa:
Sorry, lost track of the requirements.
Measure a voltage with the Arduino, display it on an LCD, and then log it, with time.
A common Arduino can't log and hasn't got a clock.
So why use an Arduino if you're going to send everything to a Pi.
Anything else this setup has to do?
Leo..
Don't be. I am thankful for your ideas. We need to store the analog input (0-11V) with the time at which it was measured. This would be later converted to the required parameters based on the initial calibration.
The plan was to use Arduino to read the analog data (0-11V) and then store it in Pi. Pi is then used to display the values on the monitor continuously.
We need a resolution of ADC of about 16 bits or more, which came up just recently.
Direct link with Pi (3.3V digital input) was not selected because of the input voltage range (0-11V analog) or else we had to find an ADC that could convert 11V DC to 3.3V digital signal. We needed the Arduino to read the analog data. We also need a user interface (if possible) to control the rate at which the data is collected and stored, which is why Pi was chosen.
Looking for your suggestions.
Use an ADS1115 with voltage divider on the input. Can be read by the Pi over I2C. No Arduino needed.
wvmarle:
Use an ADS1115 with voltage divider on the input. Can be read by the Pi over I2C. No Arduino needed.
Thank you.
+1
Use a voltage divider to output 2.048volt max (10k:47k).
Then set the ADS1115 to a PGA gain of 2.
Leo..
Wawa:
+1
Use a voltage divider to output 2.048volt max.
Then set the ADS1115 to a PGA gain of 2.
Leo..
voltage divider seems like a must use option. Is there any ADC which could take in 0-11V analog input?
There probably are, but those also would require a >11V supply voltage to be able to measure the high end.
What do you have against a voltage divider? It's cheap and effective. Do use good quality metal film resistors (low temperature coefficient, low noise).
It is because we have to solder it up to the experimental rig, just the resistors. All other items come in a casing and could be easy to place inside the rig.
The LVDT is supplied with a voltage of 15V and it could be supplied to the ADC that could take in 11V analog signal and give a signal in the 0-3.3V Digital range of the Pi. will it work?