I want to connect my Bourns pot to ADS1115. I've read to avoid noise it's better to have a Low Dropout Voltage References. I decided to use REF195GPZ. So, here I have a scheme. And before I start putting things together I want to ask you if it's a right way of thinking? Please tell if I'm doing anything wrong. I found these schemes in datasheets. Another question is if I decide to connect another pot, should I create another REF or I can use the same?
Yes, you can share a reference.
And as long at the voltage to the pot is the same as the reference voltage, noise shouldn't be big problem... If the ADC reference and the pot-voltage both drop by 50%, the ADC reading shouldn't change (at least in theory).
But, there are lots of (potential) sources for noise and at 16-bits I wouldn't expect perfectly-stable readings.
Not sure why you want to use a 16-bit A/D for a pot.
Are you sure you can adjust the pot manually to 65000 different positions.
A pot is ratiometric, and should be powered from the same reference voltage as the A/D, but the reference of an AD1115 is not exposed. Powering the pot from a different reference is a poor solution.
Why a 5volt reference.
The A/D does not reach full resolution at that voltage (only 1.024 or 2.048 or 4.096 does),
and the reference has a dropout voltage (needs a higher supply than the reference).
Leo..
Sorry, I can change the voltage for the reference within a dc-dc module or any other way. Do u think that one REF195 is able to provide enough current for 3 pots and ADS1115?
If you want to go that way, then use a REF191 (2.048volt) or REF198 (4.096volt).
Only then you can use the full range of the ADS1115 (by selecting the right PGA setting).
Tofer:
Do u think that oneREF195is able to provide enough current for 3 pots and ADS1115?
You didn't post the resistance of the pots.
If they are 5kB or 10kB (B=lin), then there shouldn't be a problem.
Again, a REF195 would need a >=6volt supply to work, and only part of the A/D would be used.
Leo..
Wawa:
If you want to go that way, then use a REF191 (2.048volt) or REF198 (4.096volt).
Only then you can use the full range of the ADS1115 (by selecting the right PGA setting).
You didn't post the resistance of the pots.
If they are 5kB or 10kB (B=lin), then there shouldn't be a problem.Again, a REF195 would need a >=6volt supply to work, and only part of the A/D would be used.
Leo..
Which part of ADS? Which resolution will I have with 5V? Are there any formula to calculate it?
And what if I have 5V on pot and ADS? Does it make sens to have the full resolution?
I think you need to read more datasheets.
Unlike the Arduino, full range is not reached at 5volt.
Page 13 of the ADS1115 datasheet has the PGA table.
Is this to control the position of a servo (your previous posts).
Why do you think you need more than a 10-bit resolution (0.1%).
Leo..
I need it for a precise focusing system. I found out that 5V is around 26 666 positions, which is already a lot comparing to 1023 of Arduino.
Now I'm struggling with my reference. I had to give it 6.4V to get 5V cause if the dropout. I didn't have such a power source, so I had to use my xl6009, which had happened to be definitely useless for my servo. I measured the voltage on my reference and in the first second after turning it on it raised to around 8-13V and then slowly goes back to 5.0V which is unbearable for ADS1115. Seems I have to change smth in my reference scheme. I'm thinking about adding a Zener diode with a resistor before my reference to make the voltage a bit more stable.
Just replace the REF195 for a RF191, and power the pot from that voltage (2.048volt).
Then set the PGA of the ADS1115 also to that voltage.
Leo..
I found the solution with REF195. Just changed analog GND to a digital GND for all my caps and it started to work just perfect without a DC-DC converters:) I think I'm fine with ref195, cause my pot can provide just 5000 positions and 26 666 from ADS is enough. I'm waiting for my ADS from Ali. Hope it will work fine all together.
Tofer:
Hope it will work fine all together.
I doubt it.
For 5000 positions, your pot power/reference voltage needs to be stable within 500uV.
Not possible if you power a 5volt reference with 5volt.
It seems your aiming for more A/D values, but ignoring the needed higher accuracy/stability. Fake values.
You could have done the same by oversampling Arduino's 10-bit A/D.
Leo..