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DRV8816: DRV8816 EVM using a uni-directional solenoid

Part Number: DRV8816
Other Parts Discussed in Thread: TM4C1290NCPDT

Hello,

I am using a DRV8816 EVM board to run a uni-directional solenoid using three methods.

Method 1: The solenoid is connected between the OUT1 and OUT2 pins. The solenoid works fine using this method. The plunger travels completely back and forth.

Method 2: The solenoid is connected between the OUT2 and SENSE pins. The plunger travels completely to one direction (the coil is compressed). But, when the voltage is reduced to 0V with the POT, the plunger does not move back to the initial condition. I can see that the plunger is trying to move, though.  

Method 3: The solenoid is connected between the OUT2 and the ground pins, but this way I cannot measure the current flowing through the sense resistor because the ground pin bypasses the sense resistor.

My questions are:

1)     Do I need to add a diode for an EMF protection across the solenoid?

2)     Could you please explain why the solenoid does not work the same way as Option 1 when Option 2 is used? What is causing the strange behavior for Option 2?

Thanks,

  • Hi Peace,

    1) Do I need to add a diode for an EMF protection across the solenoid?

    You should not need a diode because the low side FET has a body diode. As long as there is a connection from the SENSE pin to GND (directly or through the sense resistor), the body diode will re-circulate the current.

    2) Could you please explain why the solenoid does not work the same way as Option 1 when Option 2 is used? What is causing the strange behavior for Option 2?

    Can you provide some additional information?

    How are the inputs (ENx/INx) driven in methods 1, 2, and 3?
    In method 2 and method 3, does the plunger travel completely back if you provide more time?
  • Hi Rick,

    For Method 1, I noticed that both EN1 and EN2 have to be enabled (3.3V). I set IN1 to zero with the POT (RP1) and RP2 for IN2 was turned clockwise until the plunger was fired.

    For Method 2, the only input difference is the enable pins.  EN1 is zero and EN2 is 3.3V.

    As for your last question, the plunger travels back very rarely unless the EVM power is reset.  The plunger moves more smoothly with Method 1, and it moves back and forth 100% of the time as compared to using Method 2.

    For our design, we must be able to see the typical solenoid waveform from the VPROI pin to detect the solenoid movement and to find out if the solenoid is open.  We're planning to use an ADC of the TM4C1290NCPDT, and I think I need to add a filter because I can see 1 MHz noise from the EVM.  Which resistor value would you recommend between an ADC and VPROPI?


    Thanks,

  • Hi Peace,

    If you plan to use method 2 or 3, please provide scope captures of the input (IN2) and output (OUT2) voltages.
    For method 1, please provide scope captures of IN2, OUT1, and OUT2 for comparison.

    Assuming you plan to use method 1, you can use a 100k resistor and 1000pF capacitor as a starting point for your filter.
  • Hi Rick,

    I mounted the EVM board using method 1 on another board for our firmware engineer to use it, so I am not able to provide the scope catures that you requested.

    Thanks!