"H" Bridge Motor Control Circuits

  This page features H-Bridge circuits used for controlling direct current motors. Several designs are shown using both CMOS and Bi-Polar power devices.

  These circuits could be used as the basis for Model Railroad DCC Boosters or PWM motor controllers.

3Amp - DCC Booster Circuit #1 (LMD 18200)

  The first schematic is for a basic 3 Amp - DCC Booster using the LMD 18200 CMOS, H-Bridge.

  Included in the design is a 5Volt regulator that supplies power to the DCC signal generation and display circuitry.

  This circuit was designed be used with the MiniDCC© system. - A DCC ( Digital Command Control) do-it-yourself project...

Basic 3Amp DCC Booster Circuit schematic

General Purpose - DCC Booster Circuit #2 (LMD 18200)

  The following schematic is for a 3 Amp - DCC Booster with automatic shutdowns for DCC signal failure and high current loads. This circuit also uses the LMD 18200 CMOS, H-Bridge.

  This booster was designed for with the Final MiniDCC© System located at this web site.

General purpose 3Amp DCC Booster Circuit schematic

Comparator Controlled H-Bridge Circuits (LM311)

  The next two circuits are simple Bi-Polar H-Bridge circuits. The bridges are controlled by a pair of LM311 voltage Comparators.

  The LM311 Voltage Comparator has several unique features, one of which is an output transistor with an open emitter as well as the typical open collector. This allows the output transistor of the comparator to sit between the bases of the power transistors.

  The LM311 Voltage Comparator also has a STROBE input that will turn off the output regardless of input conditions.

  The circuit is shown in two configurations. The first is a typical two input bridge. The second circuit has a single - duplex input that would be used for model railroad "DCC" control applications.

LM311 Comparator Controlled H-Bridge schematic

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Please Read Before Using These Circuit Ideas

  The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.

  If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.

  Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.

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