H-Bridge Circuit

Another simple H-Bridge circuit

You have 4 transistors, wired as ON OFF switches. Two signal lines allow you to run the motor in one direction, when reversed, the motor runs in the other direction. It's very straightforward to use and build, but be careful to use only small motors, as the currents drawn from the bigger types can burn your components. An H bridge is a kind of circuit you use to control the direction (and sometimes speed) of an electric motor, using only a single polarity voltage (you need to reverse the way current flows in order to reverse the way the motor rolls)...

The circuit presented on this page attemps to be an interface to convert pulses such as provided by a Basic Stamp or R/C receiver to a dual PWM(Pulse Width Modulation) signal required by an H-bridge. The simplest circuit would use a small microcontroller like a PIC. This circuit takes a more traditional approach. Many experimenters will have all the parts already...

Two inputs, A and B, control the bridge. With both high (or open circuit) both ends of the motor are connected to 0v. Connect A low and Tr2 turns on causing the motor to go forward. Connect B low and Tr6 turns on, reversing the motor. If A and B are both low, both ends of the motor are high, so the motor is off...

This is the six transistor "Tilden style" H-bridge; while not as old as the original "basic H-bridge," this goes "way back," and is the basis for many BEAM driver circuits Up to 800 mA capacity (using PN2222 and PN2907 transistors) 30 connections per bridge (so, 30 holes if you make a PCB) Not "smoke-proof" (i.e., it can`t handle drive voltage in both directions at once)..

You can drop all off the transistors and resistors if your motors don't drain too much current. You only need a 74F139 or 74S139 NOT the LS version. The chip can provide peak currents up to 100mA for a short time (<1 second) and to one output at a time. This is for normal connections. I don't know how far you can go with this misbehavior. It's nothing special, but you get the idea how it is done...

This H-bridge variant was one of the first in which the reversing circuitry is built into the driver, rather than (as is more-commonly done) into the control circuitry upstream of the driver. This is a handy circuit, though, for 2-motor walkers -- as all that is required to reverse one is to reverse the phasing of one of the motors...

Figure 1 shows how to position a mechanical device into four discrete positions but with only two free outputs and one free input from the control system. The position depends on a set of cams and four corresponding limit switches. The 24V-dc motor comes with a worm gear. Darlington transistors Q3 to Q6 and resistors R7 to R12 form an H-bridge that drives the dc motor, M. Diodes D3 to D6 protect these transistors from inductive spikes...

The circuit shows a full bridge of four MOSFETs. In forward drive, current must flow in the direction of the pale green arrow A from battery positive, through Hi1, through the motor and so through Lo2 to battery negative. In reverse drive, current must flow in the direction of the red arrow C. With the current state of ICs and N channel MOSFETs, only a fool or a masochist would use the hi-side as the main active switching element, so it is normal to apply PWM to the loside MOSFETs, and to let the Hi-side ones take a more passive role...

The interface uses a PIC16F876 microcontroller and not much else. It performs channel mixing, current limiting, and noise rejection. Push the stick forward, both motors move forward, move the stick to the left and the robot moves left. It makes the robot very driveable. You can use a wheel transmitter meant for cars to control it, in other words, one channel is throttle(both forward and reverse), the other steering...

No description available...

A very popular circuit for driving DC motors (ordinary or gearhead) is called an H-bridge. It`s called that because it looks like the capital letter `H` on classic schematics. The great ability of an H-bridge circuit is that the motor can be driven forward or backward at any speed, optionally using a completely independent power source...

H-Bridges are often used to control the speed, position or torque of DC and stepper motors. Traditionally implemented with either discrete or monolithic bipolar transistors, fully integrated solutions are becoming increasingly popular in printer, plotter, robotics and process control applications that require 0.5A to 3.0A and operate from 12V to 55V. The LMD18200 was designed to operate within this range and was optimized for such applications...

When I designed my general purpose H-bridge circuit board, I provided a jumper for each bridge. With no pins connected, the brake is disabled. With a pair of adjacent pins connected, the brake is applied by either a (0,0) input, or a (1,1) input, depending which way the jumper is connected. Of course, for a specific application it isn`t necessary to provide an actual jumper block...

When I first started tinkering with this circuit, I made the assumption that the inverters pictured in Steve`s diagram were not intrinsic parts of the bridge, but instead were examples of the outputs coming from the "driving" circuit. This is very, very wrong. If you don`t include inverters (or, at least buffers) on the control inputs, you now have to take great care to avoid having the bridge influence the circuit that`s driving it...

There are two logic level compatible inputs, A and B, and two outputs, A and B. If input A is brought high, output A goes high and output B goes low. The motor goes in one direction. If input B is driven, the opposite happens and the motor runs in the opposite direction. If both inputs are low, the motor is not driven and can freely "coast", and the circuit consumes no power. If both inputs are brought high, the motor is shorted and braking occurs. This is a special feature not common to most discrete H-bridge designs, drive both inputs in most H-bridges and they self-destruct...