ADS1115 Unstable Measurements - Mycodo - Radical DIY Forum

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Mycodo Roberto June 5, 2021, 6:45pm 1 Hi, connecting all 4 inputs to 3.3v i get these charts. chart

chart1200×1200 110 KB chart2

chart21200×1200 123 KB I don’t know why these measures are unstable. i really need this a/d for connecting ec-ph modules and hall effect current sensor. 3.3v supply is stable, 5v fluctuates to 4.55 from 4.62. I used both supply voltage for test. KyleGabriel (Kyle Gabriel) June 5, 2021, 10:56pm 2 Can you show me a graph of several measurements when connected to a battery? Roberto June 6, 2021, 4:29pm 3 I connected an old 5v usb battery to raspberry but nothing changed. Output from battery 4.98V - 5.03V Output from raspberry (4.42V - 4.63V) and 3.28V stable. Trying to supply ADS1115 with 3.3v, measures remains unstable. chart3

chart31200×1200 94.3 KB KyleGabriel (Kyle Gabriel) June 6, 2021, 5:00pm 4 There are a lot of things that can cause what you’re observing. It appears to be operating normally after seeing the accuracy when connected to a battery, so it is likely your power supply that is the issue. 4.6 V is also an insufficient voltage to power a Pi. Additionally, the circuit you’re using the ADS1115 in can have a significant effect on noise (e.g. does the circuit have ferrites?). Last, the number of measurements you have set to average also affects the ability of the software to smooth outlier measurements. Roberto June 6, 2021, 8:04pm 5 Where? I have 3A 5V power supply and voltage is stable. 4.6V is the voltage in gpio pin for supply the ADS1115. Stabilizer inside Raspberry lowers the voltage. I found the problem right now. i need two input modules for using your new PH/EC read function and at the same time use the remains two input for other purposes. But clearly that’s not possible. So, deactivating one of two modules, measurements become stable. Do i need to buy another ADS1115? KyleGabriel (Kyle Gabriel) June 6, 2021, 8:34pm 6

But clearly that’s not possible.

You can create a new Input with pH/EC measurements and voltage from the other 2 channels. Open each Input to learn how they both work and take the relevant parts from each. Import your new Input and you’re good to go. Roberto June 6, 2021, 9:53pm 7 The problem is exactly this. I am already using two inputs for the same ADS1115 and this cause conflicts. If you integrate all 4 ADS inputs in PH/EC would be better, i think. But i can solve it by using another ADS. it also not possible set the number of measurements to average in PH/EC inputs. I have another big problem, i don’t know if i should open a new post for this. Using PH/EC input i can’t calibrate the probes. Here is the voltages… I don’t know, is it normal?SKU SEN0244 EC sensor moduleEC 200 - 0.4V 1400 - 2V 4300 - 2.3VPH4502C PH sensor modulePH 7 - 3.0V 6 - 3.1V 4 - 3.5V KyleGabriel (Kyle Gabriel) June 6, 2021, 10:02pm 8

it also not possible set the number of measurements to average in PH/EC inputs.

All the more reason to create a custom Input like I suggested.

Using PH/EC input i can’t calibrate the probes.

Why not? Roberto June 6, 2021, 10:33pm 9

All the more reason to create a custom Input like I suggested.

maybe i didn’t understand what you said to me.

Why not?

after calibrating PH4 and PH7, if i measure PH6, this is totally out of range. Same thing for EC i think this is another reason to create the custom inputs that i didn’t understand. Could you explain to me? Do you talking about rescale method with equation? KyleGabriel (Kyle Gabriel) June 6, 2021, 10:45pm 10 As far as I know, the calibration works. This module was created recently and I know of no issue with it. Perhaps you’re not calibrating properly.You would create a custom Input to be able to do all the things you mentioned (measure pH, EC, and the remaining 2 voltages). KyleGabriel (Kyle Gabriel) June 6, 2021, 11:00pm 11 Here’s the thread where the ADS1115 pH/EC Input was created:How to create a custom input with calibration using ADS1115 ADC and Gravity... Mycodo inputecphadcAt present I have some EC and pH sensors (not from Atlas Scientific) that I’ve connected to an ADC (ADS1115) and it is possible to manipulate scaling constants and conversion equations by hand to obtain calibrated outputs. However, I’m hoping to... Reading time: 8 mins 🕑 Likes: 15 ❤ dookaloosy June 7, 2021, 5:33pm 12

SEN0244

Just jumping in here. This part number appears to be for a TDS probe, not an EC probe. I know the working principles are similar, but without knowing exactly how this TDS sensor board is designed it’s hard to know what is going on. In the EC probe that I used to prototype the pH/EC custom input, the EC sensor board perturbs the pH measurement and must be modified to filter out the galvanic offset. I made a post about it on the old forum here.

4.6V is the voltage in gpio pin for supply the ADS1115.

Not sure what this means. Are you trying to power ADS1115 from the Raspberry Pi GPIO pin?1 Like Roberto June 7, 2021, 7:32pm 13

You would create a custom Input to be able to do all the things you mentioned (measure pH, EC, and the remaining 2 voltages).

Now i understand. I tried to import ads1115_analog_ph_ec. I was hoping for this feature, but ther’s too much to learn. I need time.

I know the working principles are similar

working principles is the same, diference is just a conversion.

I made a post about it on the old forum here

I will try to use your script, but before i need to understand what you have done, because, as i said, python is new to me. And i need to learn more about mycodo. So, i’m sorry to proceed slowly.

Not sure what this means. Are you trying to power ADS1115 from the Raspberry Pi GPIO pin?

Sorry, 5v pins, no gpio dookaloosy June 8, 2021, 1:53am 14 You can do an experiment without bothering with Custom Inputs. Just set it up as a regular ADS1115 as you have done.

Connect both pH and TDS probes to their sensor boards, and connect each sensor board output to two channels on the ADS1115.

Make a voltage measurement of the pH sensor output with the pH probe only inserted into the solution. Do not insert the TDS probe into the solution. Note this voltage.

Now insert the TDS probe into the solution, and see if the pH sensor voltage changes.

If the pH sensor voltage changes when the TDS probe is inserted, then you are seeing galvanic effects from the TDS probe. You will need to solve this first.