The BEAM Circuits Collection is a
Inverter buffered H-bridges
Two independently-developed, but very similar designs use a
to buffer inputs to a 4-transistor
Wilf Rigter was first with his HC bridge:
Over the course of several posts, Wilf had this to say
about his design:
Here is a smokeless design I will call HC-bridge
because it combines the best features of the H
bridge and CMOS
motor drivers. It has forward, reverse, freewheel
and brake modes.
For low voltage
applications (ie 1.5V or 2.4V), the HC-Bridge
can be further simplified by using direct transistor
drive (no base
since the base
is limited by the HC output resistance.
That "baseresistorless" design was used more
recently in the uRover circuit.
Manfred Schaffran followed a few months later with his SH
(solar H-) bridge:
Manfred had this to say about his circuit:
I had a few problems with the 74HC240
motor driver. So i designed a new (?) motor driver
for higher current
Meanwhile, Wilf had his own comments on the design:
The single input direction control option of the
SH-Bridge is a nice touch. With fewer components required
for a two wire h-bridge control circuit
with "standby" but without "brake" your circuit
wins on that count.
Note that the SH-Bridge uses one HC driver output also
for logic level inversion so [in a two wire control
form] it cannot be used without a base
But the original three wire SH-Bridge can certainly be
used at 2V without base
Note too that one of the unique features of the SH bridge
is its provision of a separate enable line, and accompanying
standby mode -- a very handy feature for low-voltage
(likely solar powered) 'bots.
For more information...
Wilf's presentation of the HC bridge came in a
groups post here
(and a corrected version posted here);
Manfred's introduction of the SH bridge came in a
groups post here.