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I've decided to make a quadcopter but since I'm a rookie, i decided against doing it from scratch. I'm planning to order this kit, first understand the dynamics and then try and make a quadcopter on my own using the components in it. My first question are

  • Can I control the 4 motors using 2 H-bridges (L293D)?
  • Are ESC's necessary if I use the PWM pins?

Thanks in advance!

  • I don't think this is Uno related. I think everything the copter needs is already in the kit. – Len Jul 14 '16 at 11:11
  • I want to make a copter on my own, with the Arduino, not with this kit. – Souvik Saha Jul 14 '16 at 11:12
  • Alright, didn't read correctly. I don't know about ECS as I don't know what it is. About the h-bridge, as far as I know you need 1 per motor. – Len Jul 14 '16 at 11:16
  • I have used 1 L293D to control 2 motors before @Len – Souvik Saha Jul 14 '16 at 11:22
  • That's because the L293D has four half H-bridges, so 2 H-bridges in total. – Len Jul 14 '16 at 11:27
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Can I control the 4 motors using 2 H-bridges (L293D)?

Yes. Two per chip.

Are ESC's necessary if I use the PWM pins?

There is one thing you must understand first: there are two kinds of DC motor - Brushed and Brushless.

The Brushed motor is the "normal" kind - you apply power to it and it spins. These you control with the likes of an L293D and use PWM to control the speed.

Brushless motors are the kind you have in hard drives and the like. They consist of a number of coils that get turned on and off at the right time to pull a magnet around in a circle (to put it crudely). These require special timing and control to get the coils energised at the right time and in the right way. This is what an ESC is for.

Brushless motors are smaller and lighter for the same power than brushed ones. They also have a longer life. Because of this they are generally preferred to brushed motors on quadcopters.

Brushed motors have a very high starting torque, don't require complex control logic and use less energy when not running full speed.

If you use brushless motors, which ideally you should (though I can't tell what kind of motors those are in that kit) then you must either use an ESC or build your own ESC using an Arduino and multiple motor driver circuits. Simplest to use an ESC.

If you don't use brushless motors then an ESC is not what you want to use - just the L293D chips and PWM.

  • Thank you for the answer. The motors in the kit are coreless motors – Souvik Saha Jul 14 '16 at 11:50
  • I saw that. I don't quite know what that means. It looks like they have 2 wires, which makes me assume they are probably brushed. – Majenko Jul 14 '16 at 11:53
  • To be clear (because I was going to answer "No, you can't"), you need 4 H bridges to control the 4 motors on a quadcopter. It just so happens each L293D already had 2 H bridges so you only need two L293D chips to get the jobs done. Right? – st2000 Jul 14 '16 at 12:12
  • That is correct. – Majenko Jul 14 '16 at 12:13
  • A coreless motor is, by the look of things, a brushed motor. – Majenko Jul 14 '16 at 13:24
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I fully agree with the answer of Majenko but I think something is missing in the explanation.
When you say "I want to control a motor" then it is not yet clear what is needed. There are the following options
1) on/off in one direction (forward).
2) on/off in 2 directions (forward and backwards).
3) on/off in on direction with speed control.
4) on/off in two directions with speed control.

For a brushed dc motor this can be achieved with.
1) a single pole single throw relay (this is similar to a on of switch)
2) a single pole single throw relay and a double pole double throw relays (this is a on off switch and a switch to change the wires to the motor)
3) a mosfet (this is similar to a single pole single throw switch that can go on/off very fast)
4) a H bridge. That is 4 mosfets that are controlled in a certain way.

Now here comes the trick: H bridges often come in 2 half H-bridges. And with a half H-bridge you can control a motor at level 3.

In other words ... with a chip that has 4 half H bridges (an as such 2 H- bridges) you can control 4 brushed DC motors at the level 3 (forward speed controlled) or 2 brushed DC motors at the level 2 (back and forward speed controlled).

  • I'm planning to use an Adafruit Shield, to control a quadcopter. – Souvik Saha Jul 15 '16 at 11:09
  • This board comes with support to control 4 brushed dc motors in 2 directions. because of the latch chip and a control library you can not control the separate half bridges (easily?). – jantje Jul 15 '16 at 13:05
  • I'm sorry, but I didn't get get you @jantje – Souvik Saha Jul 17 '16 at 7:37
  • @souvik because of the hardware you selected everything is available for 4 brushed dc motors controlled in 2 directions and with speed. You can not control 8 motors on level 3. But you don't care. – jantje Jul 18 '16 at 11:26
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You also need to consider the current needed by your motors (they are DC brushed indeed) and the power/energy you will lose in your driver.

If you use a 3.7V power supply like provided, and the L293D "eats" 1.2V out of it, you lose nearly one third of your energy. See https://electronics.stackexchange.com/questions/108686/what-h-bridge-drivers-are-preferred-for-applications-controlling-a-low-voltage-m for an very interesting review of drivers.

If I can believe that, it looks like DRV883x is the only reasonable choice. It even allows you to use one cell (3.7V) for the logic and 2 cells (7.4V) or more for the motors. But don't do that with the motors you've got, you'd probably burn them.

Unfortunately the other ST or Allegro devices also covered in the article all need more voltage to work.

Regarding the Arduino, a UNO can't be recommended, too heavy, 5V only, power hungry etc. It won't fly. I'd recommend you use a pro mini 3V3 with some LDO power supply such as the TPS73633. Be careful that most LDO regulators (like 1117) have a too high dropout voltage to be used with a 3.7V input, more than 1V.

I'm not affiliated with TI at all, it just happens that when looking for "the right chip for the right job", I keep having to eliminate the others because of data sheet numbers.

On the SW part however, it becomes difficult to find SW for the 328P. Most addicts have moved to 32-bit CPUs. But that's another debate.

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