Hi,
I'm designing a genertal purpose microcontroller board, for educational purposes and using a Microchip PIC18F452 processor. I decided to add some 'real-world I/O' in the form of a H-bridge, to drive DC motors etc. Initially, I was going to use the classic L298 device able to source 2 amps, but since this is a bit old now, I wonder if anyone could point me toward a better device, more suited to the demands of robotics?
Thanks, Peter Moreton (pete_moreton AT yahoo DOT com
The problem with the L298 is that it is a bipolar device - you will get about a 1.5V drop across the device with lots of heat. Don't believe that you will get 2A per channel - not without a massive heat sink and fan.
I've switched to the LMD18201 - a MOSFET H-bridge. It has virtually no voltage drop and therefore very little heat. Use the LMD18200 if you want current sensing. This H-bridge will indeed handle 3A with a normal-sized heat sink. The only disadvantage vs. the L298 is that it is a single H-bridge.
BRW
There is another distinct disadvantage: The LM1820x requires a minimum of 12V motor supply to operate, or its internal charge pump can't generated enough drive for its output fets. So if you're thinking of using lower voltage motors and battery supplies common in robotics, the
293 derivative may still a better choice.The TI replacement for the L293 is a better, more modern part, 754410.
Hello again I forgot to mention that the LMT 18200 has a odd pin spacing. Check out this site. They have a LOT of robotic info PLUS a PC board for the LMT
18200. Imma.......immaroadrunner wrote:
True about the 12V. I had forgotten about another advantage of the LM1820x. It has built-in flyback suppression diodes whereas the L298 doesn't.
BRW
Thanks for everyone's input - I had looked at the LMD18200 but passed over it since it costs about £14 (for a single H-bridge) in the UK, whereas the L298 is £3 (for two bridges).
I recently was considering this same question. I wanted an H bridge which worked on less than 12V, could handle 2A or 3A and was reasonably efficient. I ended up picking the Motor Mind C which has these features and controls two motors via a serial interface. In the U.S., it costs $50. The only thing I don't like is the 1.2 KHz PWM frequency (can be switched to 19.2 KHz with some resolution loss - I haven't tried it yet to see if this is acceptable).
Mitch Berkson
Take a look at Microchip TC4423,4,5. These are 3 Amp drivers, two drivers per 8 pin chip. It's not technically an H-Bridge, but each driver in the chip is a half H-Bridge. If you use the TC4425 you can drive a motor using locked anti-phase.
I was just browsing the spec sheet for the NJM3770A
A single H bridge driving 1.8A max at up to 40V. I do like it's triple comparator setup giving you a limited microstep, could also be very handy if you wanted to drive a variety of motors.
Heat sinks could be tricky though.
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