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High-side driver recommendation? — Parallax Forums

High-side driver recommendation?

MicksterMickster Posts: 2,693
edited 2019-06-19 05:37 in General Discussion
Inductive load, typically 2A @24v DC.
These are pre-wired, hydraulic-valve solenoids that I would like to PWM instead of simply switching on and off, via the existing SSR.

Edit: What I do have is a bunch of those pre-built LMD18200 modules.....I wonder if one module could be used to drive coil A and coil B? When both coils are de-energised, the valve-spool springs to the center position and the oil flow is shut off. Energise coil A for flow in one direction and coil B for flow in the other direction.

Comments

  • evanhevanh Posts: 15,915
    edited 2019-06-19 06:55
    Good to see those devices using MOSFETs now. The old darlington BJT arrangement was always blowing up or cooking themselves.

    The answer to the question is yes. Normally bidirectional motion in a DC motor is achieved by changing the direction of the average current to the two motor wires. In your case though, current flow direction is irrelevant. There is two solenoids instead.

    You can common the solenoid coils to either GND (PNP) or +V (NPN). The LMD18200 doesn't care.

    http://www.ti.com/lit/an/slva460/slva460.pdf gives a run down but it's all straight forward.

    EDIT: Corrected term used
  • MicksterMickster Posts: 2,693
    Darn it...how come I didn't find that document! Many thanks.

    As it happens, I already have the setup shown in Fig 6. (illustration #2)...Just haven't tested it yet as I have more pressing issues...that's like having two SSRs in a package that costs ~£5 (eBay) but with more capabilities.
  • evanhevanh Posts: 15,915
    Actually, it might be important wiring the coils PNP to make use of the over-current protection, which looks to only be on the high-side MOSFETs.
  • MicksterMickster Posts: 2,693
    Well it works :nerd: kinda... I can only use one side...which is all I really need... But don't understand why the other side wants to provide full current. I tried all the possibilities as per the LMD18200 data sheet but no luck.

    I am over the moon, however, because for all intents and purposes, I have this original $150 directional hydraulic valve, doing what would alternatively be a $2000 proportional valve does. Client is gobsmacked.

    Would-be entrepreneurs: There is a marketable product, right here...Phil's PWM object and a bunch of cheapie valves can save many a machine manufacturer a fortune, even with a handsome markup.
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