From ROVworld.com comes news that
New Micros has released a new
low-cost H-Bridge controller board, the NMIH-754410.
The new board has four high-current, half-h drivers designed to provide
bi-directional drive currents up to 1 Amp at voltages from 4.5V to 36V.
The board can be driven from TTL or CMOS logic. The fully assembled and
tested board is $20.
I'm assuming they mean high-current relative to the TTL and CMOS current
levels. A 1-Amp H-Bridge is definitely not what you'd be using in your
but it's a common power range for small robots. The Dallas Personal
Robotics Group H-Bridge Board is
also in the 1-Amp range (with a 3-amp peak, I believe), as are several
other common H-Bridge kits.
Like an h-bridge over troubled water, I will look down and say Hi
I guess that's how hi current is different than high current. I
looked at the picture of it: it's a dip chip on a carrier board with
no heat sinks. Because of that I'm guessing 1 amp is really really
pushing it. I'd thank at $20 it would be a great board for a modest
little robot that has less than 2" diameter gearhead motors. Probably
wouldn't want to stall the motors, and probably want to add some glue-
on type heat sink or also a little fan for more cooling. It's kinda
marginal, but for $20 though, it looks quite tempting.
That's just my guess. [insert disclaimer here]
The DPRG board uses an L298 chip which I believe will do 1amp constant
and 3amp peak. The New Micros board looks like one of those LMD293D
chips which will do like 300ma constant and 1amp peak. So when they
say it'll do 1 amp, that's really a stretch. I'm guessing this chip
on the New Micro's board is very similar to an 293 chip since it's a
DIP with no place for a heatsink whereas an L298 has a big old ground
plate with a place for a large heatsink. I'd much rather have the
DPRG board, even if I did lay it out. :-)
The New Micros h-bridge uses the TI 754410, pin compatible with the
L293D. The 754410 can sort of carry an Amp continuous, 2 A peak, and
New Micros had a cool little IC sink I saw on the ones they had at the
shop. Package dissipation is 2075 mW continuous, though. One thing that
really helps is a good size ground plane on the PCB to help dissipate
the heat. That with the IC heat sink and thermal protection circuitry
on the 754410 should make it pretty tough. I've used these on a robot
that had 2 motors that stall a bit over an Amp each, with no smoked
754410 yet. Clay T smoked one on a robot of his, and Chuck McM did as
well, but ya just shouldn't try to run big motors with these. TI
We did a thorough test of the 754410 versus the venerable L293D. We got
a marginal amount of additional power from the 754410 (practically
neglible), but also discovered that the L293D has the surprising
benefit of having input logic levels of Gnd to Vcc - of the supply
Yup, you can run logic "high" as high as your chip supply, being as
high as 36 volts. If you're really into a tight spot with no way of
accessing TTL/CMOS logic levels, screw'em! Use the Vcc of the motor
Of course, the 754410 has standard inputs, so going too high on the
inputs will toast it.
For the difference in price and availability, a properly heat-
L293d is practically as good as the 754410.
Funny for all the
advances in electronics, motor drivers have fallen back to being uC
controlled FETS for the most part. Check a hard-drive PCB when you get
the chance - it most likely will have 4 easily identifiable FETS, not
an all-in-one IC. It's either that, or one of the newer SMT-style
Allegro (or similar) devices that aren't available in DIP packaging...