What was the answer to 18v on the servo rail?

[deepsouth (DeepSouth ROV)]

Hi

What was the answer to the following?

Power Module Battery Voltage/Current Scalers

Dear EMLID, Dear Community, I have a NAVIO2 with a power module, both bought from EMLID store. I would like to monitor the battery state through the battery voltage and current signals. So far I think that the ADC is 12-bit, so the ADC.read() returns 0…4095 for conversion and -1 for error. Could anyone help me with the followings: What is the reference voltage of the ADC? The example divides the ADC readouts with 1000 and prints out [V] units. Does this mean the ADC ref is 4.096V? Wh…

I have the same issue where A1 is 18v. I know the voltage from my UBEC to the Servo rail is 5.31v via a multimeter.

pi@deepsouth:~/deepsouth/Navio2/Python $ sudo emlidtool
emlidtool version: 1.0.8
Vendor: Emlid Limited
Product: Navio 2
Issue: Emlid 2019-02-27 1548ce733215806c8ad171c8b78ebca0c7cf8395
Kernel: 4.14.95-emlid-v7+
RCIO firmware: 0xb09979ae
2019-09-03 09:18:45 deepsouth root[798] INFO gps: Passed
2019-09-03 09:18:45 deepsouth root[798] INFO mpu9250: Passed
2019-09-03 09:18:45 deepsouth root[798] INFO lsm9ds1: Passed
2019-09-03 09:18:45 deepsouth root[798] INFO rcio_firmware: Passed
2019-09-03 09:18:45 deepsouth root[798] INFO ms5611: Passed
2019-09-03 09:18:45 deepsouth root[798] INFO pwm: Passed
2019-09-03 09:18:45 deepsouth root[798] INFO adc: Passed
2019-09-03 09:18:45 deepsouth root[798] INFO rcio_status_alive: Passed
emlidtool -h to get more help
pi@deepsouth:~/deepsouth/Navio2/Python $ sudo python ADC.py
A0: 4.8480V A1: 18.1940V A2: 0.0420V A3: 0.0160V A4: 0.0200V A5: 0.0240V
A0: 4.9260V A1: 18.4030V A2: 0.0420V A3: 0.0160V A4: 0.0160V A5: 0.0260V
A0: 4.9230V A1: 18.4140V A2: 0.0420V A3: 0.0140V A4: 0.0200V A5: 0.0260V
A0: 4.9260V A1: 18.4030V A2: 0.0420V A3: 0.0140V A4: 0.0160V A5: 0.0280V
A0: 4.9230V A1: 18.4030V A2: 0.0420V A3: 0.0160V A4: 0.0200V A5: 0.0260V
A0: 4.9230V A1: 18.4030V A2: 0.0420V A3: 0.0160V A4: 0.0240V A5: 0.0280V

As an aside (and possibly related) I believe the PWM is very unstable. I am having difficulty getting a servo to work correctly in python. Its worked once out of hundreds of attempts…

[tatiana.andreeva]

Hi @deepsouth,

@deepsouth

I have the same issue where A1 is 18v. I know the voltage from my UBEC to the Servo rail is 5.31v via a multimeter.

This issue is caused by the wrong displaying of the servo rail voltage, so it barely can provoke the PWM instability.

@deepsouth

As an aside (and possibly related) I believe the PWM is very unstable. I am having difficulty getting a servo to work correctly in python. Its worked once out of hundreds of attempts…

Could you please describe your difficulties with servos in more details?

[bide]

OT, but what’s the totally tubular housing for? Is it a pressure vessel?

[deepsouth (DeepSouth ROV)]

Hi @bide and @tatiana.andreeva

@bide

OT, but what’s the totally tubular housing for? Is it a pressure vessel?

Correct. its an underwater ROV capable of depths of 100m or more. I am building my second generation version (new and improved) after successfully building my first one in January

@tatiana.andreeva

This issue is caused by the wrong displaying of the servo rail voltage, so it barely can provoke the PWM instability.

So is there a fix to the wrong display?

@tatiana.andreeva

Could you please describe your difficulties with servos in more details?

Really not much to say here. The Servo rail is powered correctly. The multi meter confirms the voltage on the pins. Running either the sample Python code or my modified version appears to correctly run (either an infinite loop for sample code, or for a set time with my code). Nothing happens. I have tried two separate servos. I have tried various pin combinations for power entry and servo (inc updating python output code), nothing works. I did get the code to work once by luck, but it was not repeatable.

[tatiana.andreeva]

Hi @deepsouth,

Does the issue persist if you disconnect everything from the Navio2 except the servo?
Do you have an oscilloscope to make sure that Navio2 provides even signal on servo rail?

[deepsouth (DeepSouth ROV)]

I have nothing connected to the Navio2 (except the RPI, servo, and power).

I don’t have an oscilloscope.

[tatiana.andreeva]

Hi @deepsouth,

Does Navio2 go through all the tests in emlidtool?

[deepsouth (DeepSouth ROV)]

Not sure why, but its currently working better right now…

[tatiana.andreeva]

Hi @deepsouth,

Let me know if you experience any difficulties again.

[deepsouth (DeepSouth ROV)]

What was the answer to 18v?

[tatiana.andreeva]

Hi @deepsouth,

@deepsouth

What was the answer to 18v?

It’s just a displaying issue. The voltage on the servo rail always remains 5V.

[deepsouth (DeepSouth ROV)]

Is there a accurate programmatic correction I can apply to the python code?

[tatiana.andreeva]

Hi @deepsouth,

You can use voltage multiplier to get the correct value. I believe you can use the multiplier in 0.284 for it.

We’ll fix this displaying issue in one of the following Navio2 images, however, I can’t provide you with any timelines.

[deepsouth (DeepSouth ROV)]

Thanks @tatiana.andreeva. I will apply the correction.

[deepsouth (DeepSouth ROV)]

Just to close this out… below is the code for the correction to the example Python code if you are seeing 18v on A1…there is a new if statement…

while (True):
    s = ''
    for i in range (0, adc.channel_count):
        results[i] = adc.read(i)
        if i == 1:
            results[i] = results[i] * 0.284
        s += 'A{0}: {1:6.4f}V '.format(i, results[i] / 1000)
    print(s)
    time.sleep(0.5)

[tatiana.andreeva]

Hi @deepsouth,

Thanks for sharing the solution!