I need to control 2 motors and I want to use the 1 amp capable H bridge. As far as I know the L293D is rated as 0.6A per motor. The L293B can handle 1 amp per motor but the pins seem to differ, or the way the motors must be connected seems not to be the same:
And a question about this IC: each motor is controlled by three pins: two for direction and the enable pin for speed; by changing the pulse widh in this pin I control the motor speed, is this right?
The diodes protect your transistors (inside the chip) from the reversed voltage peak that will occur if a voltage on a coil is shut off, like what happens in this chip and PWM speed control.
Those diodes will from a short circuit to the reversed voltage, but not for the output signal.
You need fast diodes for this, so the short circuit is reached before damage can be done to the transistors.
The motor on the left can be driven to run both clockwise or counterclockwise.
You need to drive both wires to the motor, so you need two drivers.
The motors on the right can turn clockwise only.
Here you only need to drive one wire, the other can be fixed (to GND in this case).
So you can do with just one driver.
MAS3:
The motor on the left can be driven to run both clockwise or counterclockwise.
You need to drive both wires to the motor, so you need two drivers.
The motors on the right can turn clockwise only.
Here you only need to drive one wire, the other can be fixed (to GND in this case).
So you can do with just one driver.
"So you can do with just one driver.", I don't understand, can I control the motors with just one driver?
I do uderstand what a H-bridge is, what I don't understand is the schematics with three motors connected to the L293 instead of two, and the fact that not all the motors seem to be reversible with the driver.
No, they are not fast diodes.
I would use a BYV27 (click !) (because i have a few of those available).
The generic 1n4148 diodes aren't fast and as raschemmel pointed out will probably not withstand the currents.
I mentioned fast diodes, as a lot of people building stuff like this aren't aware of their existence and purposes.
The L293 consists of 4 half bridges.
The PDF shows multiple options in 1 schematic.
You can use the L293 in any combination shown, you aren't restricted to those examples.
You can create 2 full bridges with them, 4 half bridges or any combination you like.
If you need to control 1 direction, you can do so with 1 half bridge.
If you need to control 2 directions, you need a full bridge.
If you want to control a stepper motor, you need a full bridge per coil pair.
Most hobby setups with steppers will require 2 full bridges, so one entire L293, which will probably be the reason for the existence of this package (except for the hobby part, very few hardware is produced just for hobbyists).
As you might see from this reply, there's a multitude of motor types available, and they aren't all to be powered the same way.
There are motors available that are made to rotate in a specific direction (most of those also have a gear attached).
But sometimes you just don't have a need for a motor to run in 2 directions.
So then you do not need to use a more complicated way of connecting them.
So you need to know what motor you are going to use before you are designing your electronics.
You need to know the motor anyway, because you also need to know the voltage, but more importantly the (stall) current it will take.
You might find out this driver isn't the best choice for your motor type, or maybe it is.
rva1945:
Fast diodes like the 1N4148 or the 1N914?
Fast or slow doesn't really matter because diodes are all fast on turn-on, its turn-off that
can be slow, but the free-wheel diodes only have to turn on fast to swallow inductive spikes.
(Slowness caused by parasitic capacitance isn't a problem because the inductive
spike is absorbed by a capacitor too).
Ok, so I can use the L293 the same way I would with a L293D but I have to add the diodes.
Now, how do I power a L293?
The battery (7.4V) should go into the Vcc2, PIN 8, now what about Vcc1, PIN 16? Does this one provide regulated 5V for my Arduino or do I have to power this PIN with regulated (from the Arduino board or a 7805?) 5V?
Pin 16 is a power input for the logic level of the IC.
Connect it to a 5 volt power supply, and make sure that the grounds of that power supply is connected to the ground of the power supply of the Arduino.
In case you'd decide to use the Arduino as power supply the grounds are already connected of course.
Whether or not it's a good idea to use the Arduino as a power supply depends on the load of that power supply (like how many LEDs and such do you have connected to it).
@raschemmel:
If you're replying to my reply, i didn't follow your link, thought you were linking to 1n4001 of your preference.
@MAS3,
I've been using 1N4001 - 1N4007 as flyback diodes for relays and solenoids for years because they seem to be the ones I see most in schematics I find online. When you guys started talking about how it MUST be a FAST diode I just figured "if you can't beat, join em'" so I linked this Schottky diode:
This is the first time I have seen anyone say a 1N4001 was not adequate for a flyback diode. I don't know if that's true yet.