H-Bridge Design

Discussion in 'The Projects Forum' started by Falven, Apr 19, 2012.

  1. Falven

    Thread Starter New Member

    Feb 27, 2010
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    Hello,
    I am pretty new to electronics. I want to design an H-bridge so I may switch a Linear Actuator On/Off and reverse the polarity using a microcontroller. The Motor/Linear Actuator is rated at 12V, 5A on load. The Microcontroller can generate 5V and a Maximum of 40mA to switch the circuit. How many inputs would I require from the Microcontroller? What kind of transistors and with what power ratings should I use?
    Thanks
    -Falven
     
  2. Felo

    Member

    Feb 20, 2012
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    Hi, for FFW and REV operations, you can implement with only 2 I/O, for the transistors I would use TIP 1XX, MOSFET should have smallers foot print, use a fast flyback diode across power transistor (some transistor have one in already) do a google search I've got tons of hits. Pick one and if you have anymore questions, come back here.
     
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
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  4. Falven

    Thread Starter New Member

    Feb 27, 2010
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    There are no SPDT Relays that can handle the power specifications I mentioned. What I am confused about is the schematic I would need and the power ratings for the Transistors.
    So I can just buy 4 Mosfetts (What power specs?) and set them up in this configuration, no diodes, resistors or anything and it will work reliably? What would be the duty cycle? Keep in mind I have never designed or built an H Bridge or anything similar really before so detailed help would be really appreciated.
    -Falven
     
  5. CDRIVE

    Senior Member

    Jul 1, 2008
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    What do you mean by this? Are you referring to your 40mA max uC output?
     
  6. Falven

    Thread Starter New Member

    Feb 27, 2010
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    No, what I mean by this is that there are no DPDT relays with a contact rating of 5A and a coild voltage of 12V that can be switched by my 40mA Microcontroller outputs.
    I believe a solid-state H-Bridge is my best option, but there are no IC's that can handle my power secifications either, so I need ot build one form scratch.
    My qeustion still stands...
    Thanks for the help thus far,
    -Falven
     
  7. t06afre

    AAC Fanatic!

    May 11, 2009
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  8. CDRIVE

    Senior Member

    Jul 1, 2008
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    I didn't imply that you should drive relays directly from your uC. That's what driver transistors are for. Here's a basic discrete BJT H-Bridge controlled by a uC.

    Here's a link to a marathon thread on the H-Bridge design. It includes some common pitfalls that are sometimes encountered.

    http://forum.allaboutcircuits.com/showthread.php?t=47688


    [​IMG]
     
  9. Falven

    Thread Starter New Member

    Feb 27, 2010
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  10. Audioguru

    New Member

    Dec 20, 2007
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    All your Mosfets are upside down. They are N-channel so the drain connects to positive voltages. Look at the correct schematic in the datasheet for the Mosfet driver IC.
     
  11. count_volta

    Active Member

    Feb 4, 2009
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    Ha, I actually designed this same H Bridge using relays without ever having looked at Wookie's post. Its a very easy design, and very simple and cheap. But its probably not power efficient. I have used it before though and successfully.
     
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