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DRV8412: Solenoid Driver 0-1.5A Using PWM Input to Control Current

Andrew Wrona
Prodigy 40 points
Part Number: DRV8412
Other Parts Discussed in Thread: DRV8844

I need some help with may be a simple design. I am not extremely familiar with electronics but I am a mechanical engineer (I have capacity to understand). I'm trying to develop a cheap circuit that can act as a solenoid driver with some of the specs listed below:

- 1 to 4 (or more)  output channels

- PWM input (1000 Hz and higher) to control output current (1.5 A max necessary) (normally operating to 1 A, each channel)

- Current must be controlled (temperature increase on solenoid should be compensated to maintain commanded current)

-12 V input

I'm fairly certain there may be a simple solution out there already that would satisfy my requirements but I haven't found it yet. I have seen automotive drivers which would probably work for me, but they range from $100-250 at least. I am currently using an Arduino Uno R3 as the PWM input but I am open to other low cost solutions. I have tried making a driver with a L298N board and current sensor but the Arduino analog input does not seem to register correctly. This is why I'm looking into a more robust current control method and why I have come across the DRV8412. Ideally I would be able to make this driver for ~$20-25. Perhaps there is a reason the pre-made drivers are so much, but from what I see, there's not much to what I'm asking. Does a buck converter do the things I want? Please advise.

  • 0
    TI__Guru** 114905 points
    Hi Andrew,

    Can you provide some additional information?

    What tolerance do you need for the current control?
    Do you want to change the current level or adjust the level during operation?
    Is it acceptable if the device PWM's the outputs at >20kHz without your control?
  • 0 in reply to Rick Duncan
    TI__Guru** 114905 points
    Hi Andrew,

    Is it acceptable if the device PWM's the outputs at >20kHz without your control? <- By that I mean the device has internal current regulation. The outputs are PWM'ed to maintain current even though the input is set to a static value.
  • 0 in reply to Rick Duncan
    Prodigy 40 points
    +/- 1% tolerance would be nice, but somewhere around +/- 2 to 3% would be acceptable (since this is a current CONTROL device i'm expecting error should be minimal)

    Yes, current level would change during operation. Example: current would be rampped to x level current over y amount of time and then held, similarly a negative slope ramping current back to zero amps. This control is part of the reason I started looking into a microprocessor, so that a programmed "sweep" could be used to control the solenoid(s). Currently I have a setup that has a PWM device that is control with a potentiometer. This work well, but I want to program the function of the solenoid instead of turning a knob with my hand.

    Not sure I understand what you mean about PWM outputs >20kHz WITHOUT my control. >20kHZ would be an acceptable PWM frequency for outputs.

    Thanks for the quick feedback and follow up questions Rick!
  • 0 in reply to Rick Duncan
    Prodigy 40 points

    I'm pretty sure that's exactly what I'm looking for. Previously I was going to control current via feedback from the current sensor (closed loop control?) Internal control seems faster and more stable. Any drawbacks that you see?

  • 0 in reply to Andrew Wrona
    TI__Guru** 114905 points
    Hi Andrew,

    Please look at the DRV8881E. This is an example of what I am referring to as internal control. The current is controlled using a VREF voltage and current sense resistor.

    There are EVMs of for this device for evaluation.

    One item to keep in mind is that the internal current regulation will regulate using a peak current, then enter a decay mode. This will create a current that is typically below the average current. For that reason, you may want to look at a device like the DRV8412 or the DRV8844.

    The DRV8844 is very similar to the DRV8412, but the DRV8844 has a charge pump for 100% duty cycle operation.
  • 0 in reply to Rick Duncan
    Prodigy 40 points
    Rick,

    Thanks for the recommendations. I've been looking into the details of the chips you mentioned and I had some follow up questions:

    - I see that the decay mode can be controlled, but I did not see a reference to the maximum current drop per decay option. Is this what you weer referring to in terms of tolerance of the current control?

    - I also looked into the DRV8844 and it also mentions that there is a fast and slow decay but no information on the length of the decay cycle. I understood from your comment that DR8844 did NOT have current decay, so this is a bit confusing to me.

    - What does 100% duty cycle operation mean? No decay?

    - Does TI sell breakout boards for the chips or only the EVM modules? Can the EVM modules be made without the MCU so that they are cheaper (essentially it's a breakout board without the MCU I think, so maybe this is the same question)?

    It seems like the DRV8844 EVM is $99 which is nearly in line with what I was finding elsewhere for solenoid drivers.

    Does a buck converter satisfy my requirements?
  • 0 in reply to Andrew Wrona
    TI__Guru** 114905 points
    Hi Andrew,

    - I see that the decay mode can be controlled, but I did not see a reference to the maximum current drop per decay option. Is this what you weer referring to in terms of tolerance of the current control?

    The maximum current trip point varies a few percent from device to device. Once activated, the maximum drop tolerance depends on the inductance and voltage.

    - I also looked into the DRV8844 and it also mentions that there is a fast and slow decay but no information on the length of the decay cycle. I understood from your comment that DR8844 did NOT have current decay, so this is a bit confusing to me.

    The decay cycle for the DRV8844 is controlled by the mcu. Once the desired current is reached (determined by monitoring the current through a sense resistor), the desired decay mode can be set by the mcu.

    - What does 100% duty cycle operation mean? No decay?

    Correct. 100% duty cycle will drive maximum current through the winding.

    - Does TI sell breakout boards for the chips or only the EVM modules? Can the EVM modules be made without the MCU so that they are cheaper (essentially it's a breakout board without the MCU I think, so maybe this is the same question)?

    No to both. We don't sell breakout boards or EVM without the mcu. The EVM can be modified so you can evaluate the device with your mcu.