Let's Make Robots!

H Bridge Matrix


Description

An H-bridge circuit typically provides motor control in robotic designs. Low voltage, low amperage control signals (TTL) are used to control motors. The H-Bridge can interpret these signals into a Motor Go Forward, Motor Go Backward, Motor Stop commands. Often speed can be implemented using PWM (Pulse-width modulation) through a H-Bridge. H-Bridges are extremely important in robotics. It is like the connection between the brains and the muscle of a robot. The brains being a computer or micro-Processor, and the muscles being a motor. This Matrix (when it is somewhat completed) should help you step through the process of selecting an appropriate H-Bridge design for your application.

 Terms

  • Ampere  - (symbol A) the unit of measure for electrical current
  • BJT - a common often inexpensive transistor
  • Ground - the negative part of a battery :)
  • Inductance - The magnetic field that is generated when a current is passed through an inductor, typically a wire coil. Important, because a motor which is spinning is also a generator. The current generated from this can (and has) put many H-bridges in Magic Smoke mode.
  • Load - the work a motor is doing
    • No-load - is the speed and current drawn by a motor when there is no external load
    • Stalled - is the current and torque of a motor when so much load is put on the shaft, the motor does not turn
    • Rated - maximum load conditions which the motor can be operated continuously
  • Magic Smoke - (slang) the smoke released from your circuit, which previously made it work. When a circuit becomes overloaded and components burn, they make magic smoke.
  • MOSFET - a silicon switch which is capable of switching a considerable amount of current, typically more than BJTs. Due to the fact that MOSFETs conduct less when heated, they can be ganged together to provide massive current capability. BJTs in contrast conduct more when they get hot, and will destroy themselves in similar conditions.
  • Ohm - a unit of measure for electrical resitance
  • Ohm's law - a helpful formula for figuring out how much work your circuit can do, before going into "Magic Smoke" mode. I = V/R. Current = Voltage / Resistance
  • Shoot Through - a term describing when some of the switches in an h-bridge do not open or close at the appropriate time. Shoot through shorts the power and can lead to circuit destruction. It is a good thing to avoid when possible. Some h-bridges are designed to prevent shoot through, other designs leave it to control circuitry.
  • Short - a term describing power from a circuit going directly to ground without resistance. Another good thing to avoid. It can destroy batteries, circuits, and the wire or trace which was shorted.
  • VCC, VDD, V+, VS+, PWR, + Positive supply voltage
  • VEE, VSS, V-, VS-, GND, - Negative supply voltage
  • Volt- (symbol V) the unit of measure for electrical potential/pressure
  • Sign Magnitude - a method of using 2 inputs to an h-bridge, in which one input signals direction, and a PWM input gives the magnitude of drive.
  • Locked Antiphase - input method where direction and magnitude are a single PWM input. At 50% duty the motor is stopped, lowering the duty percent would increase drive one direction, raising the duty cycle would increase in the opposite direction. Offers true 4 quadrant control of motors (CW driven, CW regenerating, CCW driven, CCW regenerating), but increases switching which increases heat.

How it works

 

 How to select the appropriate H-Bridge design

Measure resistance of the coil of your motor To find the stall current of your motor use Ohm's Law V/R=I (Current = Voltage/Resistance). For example if you measure the resistance of a motors leads at 2.4 Ohms and your battery is 24 volts, your stall current will be : 24 volts / 2.4 Ohms = 10 Amps. So if your motor stalls, your circuit should be protected or capable of handling 10 amps.

 BOA's Brilliant Hybrid H Bridge

BOA's Brilliant Hybrid H Bridge
DescriptionBaseOverApex's design of a great Hybrid H-bridge. The hybrid is a combination of relays and MOSFETs. The relays are for forward and reverse switching. The MOSFETS can accept a high frequency PWM for speed control. This design has been built (not just theory) and is currently powering one of BOA's great bots. Hopefully he will post a version of the PCB art - although it might be good to rework it so that the PIC is not part of the design, as others might be using different methods of control.
Original AuthorBaseOverApex
Built ByBaseOverApex,
Max Current10 Amps
Max Voltage12 Volts
Build Time3 Days?
Pros 
ConsSchematic is completely wrong at the moment - will fix
Max PWM Frequency 
Featuresforward, reverse, pwm speed control, current overload protection, fuse
Parts List 
Schematic
BreadBoard
Gerber

 

 BOA's Brilliant Hybrid H Bridge - Robologist Mod

BOA's Brilliant Hybrid H Bridge - Robologist Mod
DescriptionBaseOverApex's design of a great Hybrid H-bridge. The hybrid is a combination of relays and MOSFETs. The relays are for forward and reverse switching. The MOSFETS can accept a high frequency PWM for speed control. This design has been built (not just theory) and is currently powering one of BOA's great bots. Hopefully he will post a version of the PCB art - although it might be good to rework it so that the PIC is not part of the design, as others might be using different methods of control.
Original AuthorBaseOverApex robologist
Built By 
Max Current15 Amps - limit by relay
Max Voltage12 Volts to 15 Volts
Build Time3 Days?
Prosstrong, low cost
Consnot quicklyswitchable forward to reverse, limit by relay
Max PWM Frequency 
Featuresreverse flyback diodes, MOSFET driver
Parts List
Desig  Qty  Part#           Each  Total    Dist      Description
*K1,K2 2 PB897-ND $4.44 $8.88 Digikey Tyco PCLH-202D1SP,000 12VDC/75 mA coil, 15A relay
*Q1,Q2 2 IRFZ44NPBF-ND $1.89 $3.78 Digikey IRF IRFZ44NPBF 49A 55v N-chan FET TO-220
*Q3,Q4 2 P2N2222AGOS-ND 0.36 0.72 Digikey On Semi P2N2222AG 600mA 40v NPN GP BJT TO-92
*D1-D8 8 497-2753-5-ND $1.09 $8.72 Digikey STMicro STPS1545D 15A 45v Schottky rectifier diode
*U1 1 TC4427CPA-ND $1.05 $1.05 Digikey Microchip TC4427CPA 1.5A MOSFET driver
*C1 1 4035PHCT-ND 0.81 0.81 Digikey Vishay 220 uF 35 v Electrolytic Cap
* Total $23.96
Schematic
BreadBoard
Gerber

 SINGLE CHIP N-CHANNEL FET BRIDGE

SINGLE CHIP N-CHANNEL FET BRIDGE
DescriptionDesign which contains a very small amount of components for a very large capacity H-Bridge.
Original AuthorGroG
Built By 
Max Current30 Amps
Max Voltage50 Volts
Build Time3 Days?
ProsVery small number of components, includes a under current protection line, will not "shoot through"
ConsSchematic is completely wrong at the moment - will fix
Max PWM Frequency 
Featuresforward, reverse, pwm speed control, current overload protection
Parts List 
Schematic
BreadBoard
Gerber

 

 

 SIMPLE LOW POWER NPN PNP H-Bridge

SIMPLE LOW POWER NPN PNP H-Bridge
DescriptionDesign which contains a very small amount of components for a very small capacity H-Bridge. The NPN transistors can be substituted with a variety of differently rated components. 2N2222 TIP120, etc.
Original AuthorGroG
Built By 
Max CurrentDependent on the transistor used - 2n2222 can sink ~800 mA, a TIP 120 can drive 5 amps with proper heat sink
Max Voltage50 Volts
Build Time 
Prossmall, inexpensive
Consno protection of shoot through, will only drive small motors
Max PWM Frequency 
Featuresforward, reverse, pwm speed control
Parts List 
Schematic
BreadBoard
Gerber

 SINGLE CHIP CONTOLLERS

SINGLE CHIP CONTOLLERS
DescriptionDesign which contains a very small amount of components for a very small capacity H-Bridge. The NPN transistors can be substituted with a variety of differently rated components. 2N2222 TIP120, etc.
Original AuthorKrumlink
Built ByKrumlink - It is being implemented in my revised AREV-RSPF232
Max Current1.2 Amps per line
Max Voltage4.5 VDC to 40 volts (Forgot max but it is around 40 VDC) for motor lines / VCC2
Build Time 
Prossingle chip, no external peripheral stuff needed, just hook up the motors, input and enable lines and you are good.
ConsThe SN754410 does not have build in clamp diodes, so you need to add them. The internal diodes are for ESD protection  Pulldown resistors may be wanted to prevent the enable lines drifting high Low max voltage for motors but with internal diodes it drops the voltage to 3.1VDC anyways.
Max PWM Frequency 
FeaturesSimple to hook up, you do not need PWM and it is easy to throw together and use with LED's too
Parts ListSN754410 - optional pulldown resistors (1-10k usually)
Schematic
BreadBoard
Gerber 

 Simple P-channel over N-channel h-bridge

Simple P-channel over N-channel h-bridge
DescriptionBasic low part count P over N h-bridge
Original Authorrobologist
Built By 
Max Current80 Amps?
Max Voltage12-15 Volts limit by driver and configuration
Build Time2 hours?
ProsVery few parts, cheap
Cons

No shoot through protections, uses 4 inputs, untested

Could be improved by connecting upper and lower inputs, then adding an inverter attached between right and left sides for lock antiphase single input drive. Test shoot-through with uppers/lowers connected for feasibility.

Max PWM Frequency 
Featuresforward, reverse, pwm speed control
Parts List
Desig  Qty  Part#             Each  Total    Dist      Description  
*U1,U2 2 579-TC4427ACPA $1.36 $2.72 Mouser Microchip TC4427CPA 1.5A MOSFET driver
*Q1,Q2 2 726-SPP80P06P $3.02 $6.04 Mouser Infineon SPP80P06N P-ch 60V 80A FET TO-220
*Q3,Q4 2 726-IPB080N06NG $2.11 $4.22 Mouser Infineon IPB080N06N G N-ch 60V 80A FET TO-220
*C1 1 647-UVY1E221MED1TA 0.11 0.11 Mouser Nichon 220 uF 25 v Electrolytic Cap
*total $13.09
Schematic
BreadBoard 
Gerber 

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this is fantastic! i might modify this circuit to make my next robot!

Thank you very much for these great information,well appreciated :)

I am walking in the big footsteps of the mighty CTC. I have accepted the challenge of building BOA's hybrid H-bridge motor driver.

Just like Chris I'm going to control it with a picaxe.

I will be asking questions in the near future.

one question: what is the (on the schematics of "Simple P-channel over N-channel h-bridge" or "BOAs brillinat h-bridge") mosfet driver for? i tried to read the datasheet but can't understand its function.
MOSFETs need to be switched on quickly and off quickly to keep from being heated up. The longer time is spent in switching, the more the FETs are in a linear region where their resistance is much higher, causing power disspation. Getting them to switch faster requires getting the voltage changed on the gate quickly, which essentially acts as a capacitor. To charge a cap quickly means to send a lot of current to it quickly. Typical logic gates from micros, are only good for 5 to 20 mA, where a driver can push in the Amp range. When trying to switch faster, more current is needed, so where a micro tied to a gate of a MOSFET might be able to switch it at 1 kHz ok, going any higher might cause the FET to heat up as it stays more in the linear region, never completely turning off or on. Additionally, FETs switch better with a gate voltage about 10 volts above the drain level, rather than 5. There are "logic level" FETs but their operation is quicker when used with a higher voltage. THere is an upper limit on that, typically at 20 volts or so.
thank you very much, great explanation.

Robologist put that in.  My understanding of it, is that the driver allows a larger amount of current to the MOSFET gate.  I have a H-Bridge which currently is not using a driver, the gates are switched with TTL voltages, but I can imagine - that depending on your setup you might want to use one.  I chose fewer components and have not run into any white smoke ..... (yet).  :)

GroG

I swear this is the thread that will not die... If it keeps going, I think we are just going to start talking about the weather and our kids and stuff sooner or later.

--I all ready finished the damn motor controller that started all this, for cryin' out loud!!

What paginator do you use, Chris? Mine (firefox 3) still shows this entire node on one (BIG) page.

This confused me for a while as well but I think I got it. --On your relay board, the reverse happens after the PWM signal and is seperated. It is the same as switching the leads going to the motor. When you are using the set-up described above, it is an issue of High/low.

Here we go.

PWM 1

Out 2 Low 

This is FWD and 75% of the PWM pulses are High therefore 3/4 power.

__________

PWM 1

Out 2 High

This is reverse but now sence 75% of the PWM pulses are still high, 75% of the time you have a High/High situation and only a 25% Low/High situation. Now instead of the motor being on 75% of the time (3/4 power), it is only on 25% of the time AND in reverse. To get your 75% power the other direction, you need the PWM to be Low 75% of the time --Thus, 25% high!

Woo Hoo! Chris explains to BOA!!!!!! --Had to happen sometime!!