H-Bridge


Posted on Feb 5, 2014

For a project such as a robot or car, we need an ELECTRONIC circuit - one that is controlled by a `CONTROL CIRCUIT`. The Control Circuit outputs a signal (or a number of signals) to control an H-Bridge. Here is a circuit of a Hex Bug. The Control Circuit consists of the first 3 transistors. These amplify the signal from the electret microphone and


H-Bridge
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produce a signal that is able to charge a 47u electrolytic. The next two transistors provide inverted signals to the H-Bridge and are part of the Control Circuit. The H-Bridge consists of the last 4 transistors. 4. They all take a higher current when loaded - (the motor is driving a load). A load may be placing your fingers on the output shaft or driving through a gearbox and lifting a load or driving wheels via a gearbox. The torque (twisting ability of the output shaft) depends on the voltage and current as well as the strength of the field magnet and the quality of construction (the closeness of the field magnet to the armature). It must also be able to deliver a "running current" (operating current) (say up to 1 amp) and a "starting current" (up to 5 amps), and a "loaded current" (up to 5 amps). The transistors must be capable of passing a "stalled current" without being destroyed. There are a number of different H-Bridge designs and the actual circuit will depend on the number of transistors, the type of layout, the number of control lines, the voltage of the bridge, and a number of other factors. This design uses 4 transistors. Both inputs must NEVER be HIGH (this will create a short-circuit and damage the transistors). However this circuit is a good design. The voltage on the H-Bridge can be any voltage and the control voltage just needs to be higher than 1v. The circuit provides OFF feature when both inputs are LOW...




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