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ISO1211: ISO1211

Avaneesh chitta
Prodigy 10 points
Part Number: ISO1211

Hello !
 We needed help with a product design/suggestion for a circuit. 
I am Avaneesh ketan and I am working on Remotely Operated Vehicles (ROV)/Robots for Underwater applications. 
Our problem description

We control the ROVs using Joysticks, where the joystick commands are given to a laptop, the laptop is connected to a raspberry pi using an ethernet cable, and the Raspberry pi is connected to 6 BLDC thrusters. The connection between the Raspberry pi and the Thrusters is as follows.
Raspberry pi -> GPIO pins -> Control signal to Electronic Speed Controller -> Thrusters.
The problem we are facing is that, whenever we are rapidly changing the input signals of the Joystick (i.e. from upward motion to downward motion or left to right (vice versa)), the Thrusters are immediately shutting down and so is the Raspberry pi. We believe that this issue is being caused by Voltage spikes coming from the Thrusters. 
The power given to the Raspberry pi is as follows.
UPS -> SMPS (24V, 41.7A) -> Buck converter -> Raspberry pi.
Please do let us know three things
1) What can be the possible problem in our case and is it really with the voltage fluctuations ?
2) Should we use Isolators between the thrusters and the Raspberry pi to prevent the Raspberry pi to turn off ?
3) If no, what else can be a solution to prevent these voltage spikes ?

  • 0
    Guru 288070 points

    Did you measure the spikes?

    How are the thrusters supplied? Another plausible cause might be that the thrusters use more current and make the power supply drop.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 22835 points

    Hello Avaneesh, 

    Thank you for your question. 

    Based on your description, it sounds like the high current demand of other parts of the system could be causing the power supply to drop and the thrusters to lose power. Isolation would be needed if the spikes were on the ground line and were causing the communication signals to be corrupted.  

    However, please understand that communication is not granted if these spikes are causing the VCC to lose power. Also, if the spikes are greater than the absolute maximum conditions in the datasheet, the device could damage, however the isolator would still help to protect the sensitive circuitry (like the raspberry pi). 

    Best,
    Andrew

  • 0 in reply to Clemens Ladisch
    Prodigy 10 points

    Hey Clemens !
    Thank you for your response. 
    The thrusters are supplied directly from the SMPS i.e., we designed a manual PCB, which has a few parallel connections, supplying 24V to every part of the circuit. 
    The output of the PCB is directly connected to the thrusters.

  • 0 in reply to Andrew J
    Prodigy 10 points

    Hey Andrew !
    Thank you for your response.
    In the circuit which I'm using, there are no other High power demanding elements except the thrusters. 
    There are
    1) Raspberry pi
    2) Two LED Lights
    3) A Camera
    4) 6 thrusters
    I would like to also mention that we did not manually check the spikes in our case. 
    Also, are you mentioning the ethernet communication in your response ?
    Thanks 
    Avaneesh

  • 0 in reply to Avaneesh chitta
    TI__Mastermind 22835 points

    Hi Avaneesh, 

    Unfortunately, I can really only guide you through the isolation parts of your system. Without seeing a scope capture of your problem, I cannot assist with further debug. Digitial isolators would be helpful if the digital communication signals to the motors were being corrupted by ground transients (such as GPIO, I2C or SPI). Monitor the data lines with an oscilloscope to see if you are losing data connection. 

    I still suspect that your 24V supply is not sufficient to supply a quick impulse demand of all of your motors to check this, measure all of your VCC rails while the thrusters are losing power. 

    Best,
    Andrew