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H-Bridge motor driver

Vendor's Description: 


POWER H-bridge

This circuit allows the reversal of powerful DC motors type permanent magnet. Such motors are also applicable to medium-sized robots.

The voltage signals that drive the verses (forward or backward) are fitted with a suitable base of resistances which let you pass under the 10 mA required for saturation of the TIP122.

The typical switching speed of Darlinghton  transistors also allows PWM signals so the circuit is well suited to the connected motor speed control  without  theoretically loss of torque.

The design is simple and compact.

Each piece has four transistors darlighton supporting a 8A DC.


Two L.E.D. lights indicate the movement direction, Green (motor forward) Red (motor reverse).


The table shows the values ​​of resistors suitable base for connection to a microprocessor card, a card, generic to 12 volts, or an industrial controller (PLC + 24 volts DC).



Classic control tension

5 Volt

330 Ohm

12 Volt

1 K Ohm

24 Volt  (PLC control)

2,2 KOhm





Typical connection of DC Motor

Brushes applied voltage: 12V

Misured carrent whit these motor: 0,8 A (at  Vn with free shaft)

inrush peek current : 1,5A

maximum locked rotor current: 4A


The specimen in the photo has the resistance calculated to operate at 12 volts (or 1200 ohms) but can be used though it is recommended to replace them with 24V 2.2 K. The student who performed the installation does not have terminals that are to be scored from the left: (+ Engine, Engine - photos were assembled in both red), blue wire corresponds to the forward command, follows the mass of this command left open (NC) in this application, the green wire is the reverse command followed by its mass (CN), the penultimate is feeding properly mounted Positive red whose value depends on the engine used in volts, and finally the orange wire to the right is the power and mass of the entire circuit, which in the scheme presented some top line corresponds to terminal X4-2. In that PCBs are properly seated 3 mm LEDs with accuracy to mount to the cathode (the cut side of the body of the LED that corresponds to the lead shorter).

Convention on the circuit have been reported green LED forward (corresponds to LED 1) and red LED reverse (corresponds to LED 2), if the engine must be rotated in the opposite direction to reverse the two red wires connected to the first terminal on the left, that the armature of the DC motor


in some cases, where there is instability in the external system of control could be necessary to buffer or interface control signals via relays or transistors, or operational like comparator, so that they arrive at the bases of the transistors to a level of 12 volts.

when you want to drive the H-bridge PWM signal with a fast for a large DC motor is recommended to connect external free-wheeling diodes as shown in the diagram.


The two blue wires coming out of the third and fifth terminal, not related, are the control signals. If you want to interface this small PCB to your demoboard, remember to take the control voltage to +12 V inputs interposing a comparator with operational and appropriate bjt working in the area of signal saturation and interdiction.

The presence of free-wheeling diodes allow the system to be driven with the PWM techniques easily performed with the digital outputs of the PIC, and thus to have control of motor speed without loss of torque.


There are available some panels containing 10 copies of the H-bridge

the panels are sold at 25 USD each to add shipping costs


Single copies are distributed only assembled and tested at a cost of 22 USD each.

Multiple supplies can be obtained at reduced costs.

if you have to drive the motors left and right, you get two H bridges at a cost of 38 USD.

four copies can be supplied assembled and tested at a cost of 70 USD.

in any case must be added the shipping costs.


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I built the same setup on perfboard, using a TIP122 equivalent. My tranzistors had integrated protection diodes and they appear to suffice... but OddBot is right about the "accidental short logic" - I burnt my fingers on several occasions because I loaded the wrong code in the microcontroller while the default settings for the pins were shorting the battery.