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H-Bridge Motor

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beginner2

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Hi to all electronics experts.

I have a design on a H-bridge motor.

May i know can this circuit work to give 4 directions (forward, backward, left and right?) with the use of onli 1 motor (as shown in the schematic)??

or i must 2 motors in order for it to work in 4 directions?

and also for the Vcc. when i supply a 12V to the Vcc, the voltage level at the DC power supply will drop from 12V to around 4V only. May i know why could this happen?

this motor circuit movement shall be control by an interface at the PC side through a programmable Atmel 89C52 uC.

TQ.
 

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explain me plz this:
May i know can this circuit work to give 4 directions (forward, backward, left and right?) with the use of onli 1 motor (as shown in the schematic)??

one motor going into 4 directions like WHA'?!?

also where is the Vcc 4V on the schematic? and where is the 12V
 
bloody-orc said:
explain me plz this:
May i know can this circuit work to give 4 directions (forward, backward, left and right?) with the use of onli 1 motor (as shown in the schematic)??

one motor going into 4 directions like WHA'?!?

also where is the Vcc 4V on the schematic? and where is the 12V

thats why i m asking whether the above cct can drive the motor to move 4 directions onot?

and the Vcc is at the top of the diagram.
 
yes i knowthat Vcc is up there but where isit 4V as you said? you mentioned something about voltage drop. and as nigel said how do you plan to work one motor 4 ways as it yes only runs clockwire and couterclockwise.
 
Nigel Goodwin said:
A motor rotates, rotation can be either clockwise, or anticlockwise, what other two directions were you thinking of?.

so Mr Nigel is there any suggestion u would recommend to modify the circuit above in order for the motor to move in 4 direction (forward, backward, left and right)???

if i would to add in another motor to give another 2 directions, is it this way?

[quote = "bloody-orc"]yes i knowthat Vcc is up there but where isit 4V as you said? you mentioned something about voltage drop. and as nigel said how do you plan to work one motor 4 ways as it yes only runs clockwire and couterclockwise.[/quote]

the 4V voltage drop is on the DC power supply. First i set the Dc power supply to 12V....when i connect the 12V to the circuit, the Dc power supply auto drop to onli around 4V.Anyone know why this happen?
 
beginner2 said:
so Mr Nigel is there any suggestion u would recommend to modify the circuit above in order for the motor to move in 4 direction (forward, backward, left and right)???

if i would to add in another motor to give another 2 directions, is it this way?

You simply cannot move a motor in more than 2 directions (clockwise and counter clockwise). If you need to control something in 4 directions, you need 2 motors. To power 2 motors, you need 2 complete H-bridges.
 
beginner2 said:
if i would to add in another motor to give another 2 directions, is it this way?

It depends how you want to steer?, the usual method for small robots is to steer like a tank, with one motor feeding each side.

the 4V voltage drop is on the DC power supply. First i set the Dc power supply to 12V....when i connect the 12V to the circuit, the Dc power supply auto drop to onli around 4V.Anyone know why this happen?

What spec is your supply?, what spec are your motors?, and are you sure you're not switching all the FET'S ON at the same time?.
 
Nigel Goodwin said:
...and are you sure you're not switching all the FET'S ON at the same time?.

I think they will will all be partially on at any given point too.

Beginner2, every FET in existence has a certain on resistance. This means that because of the way you have your low-side FETs wired, the can both turn on at the same time. In a worse case situation, the power supply could have an almost direct connection to ground shorting it out. Another possible situation is the low-side drivers will only partially turn on causing them to dissipate a lot of heat.

Reverse EMI from the motor could also cause a number of problems.

You would have better luck controlling the high-side and low-side as 4 independent channels.
 
Well this particular topolgy will create smoke.

The top-FETS are the wrong way up, so when you start friing the intrsisic diode will complete the shoot-through with one of the lower-FETS
 
Styx said:
Well this particular topolgy will create smoke.

The top-FETS are the wrong way up, so when you start friing the intrsisic diode will complete the shoot-through with one of the lower-FETS
I think they look wrong way up because he used NMOS symbols for PMOS transistors. He does have the source/substrate tied to VCC, as a PMOS should be.
That doesn't mean this will work. Has anyone tried this? Let's say I have both NPNs off, so that the circuit is idle (see annotated schematic below). Now, if I turn on Q1, M1 will turn on first. It seems to me that M4 would turn on next, preventing M2 from briefly turning on. This would avoid the shoot-through problem alluded to by phalanx. The programmer would have to put in some dead time between turn-off of Q1 and turn-on of Q2 to avoid the other possible cause of shoot-through.
This configuration does not allow for shorting out the motor, which I believe is useful for braking, but it may not be necessary. This would require four control inputs.
 

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All I have to say is... GATE DRIVE!!!!

that is why this cct isn't going to work to its (very bad) potential
 
Styx said:
All I have to say is... GATE DRIVE!!!!

that is why this cct isn't going to work to its (very bad) potential
There is no doubt it's going to be slow, but that may be OK if it is switched infrequently.
 
so....as a conclusion....does this mean the my cct practically cannot work?

so anyone has a circuit on this?

can help me out pls?
 
please tell us what the hel* are you trying to do? what is your final objective and what part is this circuit gonna do. (or supposed to do)
 
bloody-orc said:
please tell us what the hel* are you trying to do? what is your final objective and what part is this circuit gonna do. (or supposed to do)

I have to design a motor circuit which is able to move in forward, backward, left and right directions.(the circuit will be mounted on a control car)

the movemnt of this motor circuit will be control at the PC side through an user interface created using VB6.0. When instructions is given in the PC, for example, when i click on the interface at PC side to order the car the move left, instruction will be sending out from PC to the motor circuits through a 89C52 uC(The uC will be written using assembly language). When the uC receive the "left" instruction, it will turn on certain part of the motor circuits to give the left movement.

basically this is the idea of what I need to do.
 
Nigel Goodwin said:
You say control 'car', so do you mean with car type steering?, or some other kind of steering?.

the car is a remote control car. But i wont use the remote control that comes with the car to control the car movement. Instead i want to control the car movement using interface at PC side through 89C52 uC.
 
beginner2 said:
Nigel Goodwin said:
You say control 'car', so do you mean with car type steering?, or some other kind of steering?.

the car is a remote control car. But i wont use the remote control that comes with the car to control the car movement. Instead i want to control the car movement using interface at PC side through 89C52 uC.

At last you give us a clue!.

The steering is done by a servo, you simply generate the servo drive pulses in your micro-controller - it's completely seperate to your drive motor.

I'm presuming this is a 'proper' radio control car?, and not just a small toy?.
 
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