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DRV8844: analog control and amplification for hydraulic solenoid

Ahmed Moaty
Prodigy 20 points
Part Number: DRV8844

We need your advice for our PLC control unit that is used to operate several hydraulic solenoids. 

Our case and requirements are as follows:

We have analog controlled solenoids that operate with (2 to 28 volts DC) & (0.3 to 2.5 amperes).

We need to control the above mentioned solenoids using analog PLC that gives output signal (0 to 10 Volts DC) or (4 to 20 milli ampere)

So we need a solenoid driver to operate our solenoids modulation using the PLC signal output.

 

We got your DRV8844 and we connected it as follows in a circuit:

  • We connected a 0.01 micro farad (100 V) capacitor between CP1 &CP2
  • We connected a 0.47 micro farad (6.3 V) capacitor between V3 P3 out and VNEG
  • We connected a 0.1 micro farad (16 V) capacitor between VCP and VM
  • We connected 10 micro farad (50 V) capacitor between VM & VNEG
  • LGND with the negative output signal from our PLC output
  • 1N1 with the positive output signal from our PLC output.
  • Out 1 to the negative pole of the solenoid relay.
  • VM to the positive pole of the solenoid relay.
  • Power supply to the driver positive to the VM negative to the VNEG (24 volts power supply)

After trying this setup didn’t give us our requirements.

We need to know if these connections are correct.

Also we need your advice if this any further components or additions needed for the setup to achieve our requirements.  

  • 0
    TI__Guru** 114905 points
    Hi Ahmed,

    What results did you get with the setup?

    How did you connect the EN1 signal?

    Does the positive output signal from the PLC output exceed 7V with respect to LGND? This violates the absolute maximum rating.

    How does the output of the PLC vary? Is it a PWM signal or an analog voltage?
  • 0 in reply to Rick Duncan
    Prodigy 20 points

    Hi Rick

    1- the output that we get is always 10 volts without even getting any signal from the plc ( always on)

    2- we didn't use the EN1

    3- the out put of the plc is a modulating output +ve signal with the -ve signal ( logic ground ) is from 0 to 10 volts ( but still this dont change the output of the driver under any condition.

    4-the plc can give the following - from 0 to 10 VDC

                                                             - from -5 to 5 VDC

                                                             - from 0 to 5 VDC

                                                             - from 4 to 20 mamp 

    thank you for your support

  • 0 in reply to Ahmed Moaty
    TI__Guru** 114905 points
    Hi Ahmed,

    The PLC should provide 0 to 5V. -5V or +10 violate the absolute maximum. The device may have already suffered damage.

    Please try the following:
    Remove the load, and replace it with a resistor divider (30k/10k suggested to create 6V) from 24V to GND. Connect the mid point to OUT1.
    The output should be approximately 6V.
    Set EN1, nRESET, and nSLEEP to a logic 1. These are needed to enable the output.
    If the device is operating properly, the output should now be 0V.
    Set IN1 to a logic 1, and the output should be 24V.

    Would you please provide a schematic of your connections to the device?