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| This is a 3A H-Bridge Module based on the LMD 18200 H-Bridge. In addition, this bridge offers pass-through connections for quadrature encoders, fuse protection, and an innovative Back-EMF velocity measurement circuit. This bridge is ideal for use in the BrainStem Moto 1.0 Module. This H-Bridge component is a convenient way to control motors or other high-current loads. This H-Bridge component also incorporates an Acroname-designed Back-EMF measurement circuit that allows you to actually discern the speed of the motor you are driving without an encoder! This allows you to use this component to drive motors from toys, cars, or other places where speed control was not possible before. There are three main forms of motor feedback supported with this component: Back-EMF This mode is the default jumper selection on the board and requires a specific timing sequence both operate a motor and take feedback measurements simultaneously. Current Sensing This mode is selectable through a soldered jumper and allows the current being used by the motors to be read as an analog value with 1 Volt/Amp of current. Quadrature Encoder This mode is independant of the other two and can therefore be used simultaneously with either provided the correct I/O control is used. Two channels of encoder input are passed through allowing quadrature inputs and these inputs have built-in 3.3k Ohm pullup resistors. The bridge is based on the National 18200 H-Bridge chip so it has very low on resistance (0.4 Ohm), and can handle currents of 3 Amps continuously and as much as 6 Amps surge. It also has a built in 3.15 Amp fuse (easily replaced) and incorporates seperate power supply inputs for the motors. One extra fuse is included with the module. Charge-pump capacitors are also included to offer higher PWM speeds and therefore greater motor efficiency. The pinout for this H-Bridge component conforms to the Acroname H-Bridge Standard so it will work well with any device that conforms to this standard. An encoder header is built into the bridge to allow quadrature encoder inputs to be plugged directly into this bridge component and passed through to the standard header and 3.3k Ohm pullups are included. Specifications Value Min Typ. Max Unit Motor Voltage 12 12 27.5 (1) V Continuous Motor Current 0 na 3 A Surge Motor Current 0 na 6 A PWM Frequency 0 39,000 500,000 Hz Logic Supply Voltage 4.5 5 5.5 V On Resistance - 0.3 - Ohm Notes: 1. The H-Bridge can handle up to 55V but an instantaneous change of direction can cause a 2X voltage swing so the effective max is 27.5V. This bridge component measures 2.5" by 1.35" and is just under 0.5" thick. This board is ideally suited to use on the BrainStem® Moto 1.0 module. The above photo shows one 3A EMF H-Bridge installed in the Moto 1.0 module. The Moto 1.0 module will accept two of these H-Bridge boards. Acknowledgement The idea of Back-EMF feedback for motion control was originally introduced to Acroname by Randy Sargent who, along with Bill Bailey, had worked on a similar design. This method of speed control has also been popular in audio tape mechanisms for decades and is also used in modern model train controllers. |
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