Using a common robot motor from Solarbotics. In later pages, I'll compare the performance of three different part numbers of popular transistors This H-bridge can operate from a power source as low as two nearly-exhausted 'AAA' batteries (2.2V) all the way up to a fresh 9V battery (9.6V).
That is, an H-bridge allows a microcontroller, logic chip, or remote control to electronically command the motor to go forward, reverse, brake, and coast.įor the purposes of this article, I’m focusing on a basic H-bridge that is a good choice for most robots (including BEAM robots) and portable gadgets. The classic beginner’s DC motor driver circuit that appears in every electronics textbook is the bipolar transistor H-bridge.Īn H-bridge is an arrangement of transistors that allows a circuit full control over a standard electric DC motor. The datasheets explain this.H-Bridge Motor Driver Using Bipolar Transistors Ceramic caps of 1uF will cut down the ringing. If you choose the pmos/nmos solution, use something like Intersil EL7202, if you choose the dual nmos solution, use the slightly more complex half bridge driver LTC4447Īlso you will need good power supply decoupling capacitors very near the power mosfets and gate driver chips. Use some kind of MOSFET driver chip between your control logic and the MOSFET gates. Therefore 100mW/((1.1A)^2)=0.08Ohm rDSon, with a 12V gate drive (rDSon gets higher with lower gate drives). You don't want to have to heatsink your MOSFETS so keep the power dissipation lower than 100mW. Off the top of my head, I'd recommend power mosfets with a max VDS voltage of 30V, any more than that is overkill, but the motor inductance can ring and you might see greater than 12V because of it, so you want more than 12V. A simpler approach would be to substitute PMOS for the upper power MOSFETS.
This will give you an idea what you are looking for. Linear Tech makes the LTC4447, but there are many others available. The solution would be to buy a common IC called a Half-bridge Driver or a Synchronous N-Channel MOSFET Driver. Third, if you want to use all NMOS power MOSFETS you will need to drive the upper two mosfets differently, using a floating bootstrapped power supply. Check with your scope to see that the waveforms have rise times well under 100 ns. You should aim to drive the mosfet gates with 12V square waves unless you have a good reason not to. So, you will not be able to drive the mosfet gates strongly enough. Second, the motor drive voltage is 12V, and I imagine your TTL logic voltage is 5V. If you have slow rise times on the gate, you will begin to dissipate a lot of power in the power MOSFETS, resulting in smoke and pops! First, these are power mosfets that have large gate capacitance, and TTL logic are not going to provide a fast, sharp rising edge to the mosfet inputs.
0 kommentar(er)
