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hesam_m
Posts: 16
Joined: Thu Apr 25, 2019 9:45 am

An easy to build PWM controlled DC motor driver

Tue May 07, 2019 4:41 pm

Motor driver circuits are one of the most useful designs for industrial, automotive and robotic applications. Full control over a DC motor is an essential function for a variety of applications. For many low power applications, 1A to 1.5A RMS current consumption limit/per motor is enough, therefore I selected a useful chip that can operate with just a few external components.

The DRV8833 chip is a dual H-bridge motor driver. According to the datasheet: “The DRV8833C device is an integrated motor driver solution for brushed DC or bipolar stepper motors. The device integrates two NMOS H-bridges and current regulation circuitry. The DRV8833C can be powered with a supply voltage from 2.7 to 10.8 V and can provide output current up to 700-mA RMS. A simple PWM interface allows easy interfacing to the controller circuit. The current regulation is a 20-μs fixed off-time slow decay. The device includes a low-power sleep mode, which lets the system save power when not driving the motor.”

The figure-1 shows the logic level thresholds of the chip inputs. The VIL and VIH values show that the inputs can be used for both 3.3V and 5V logic without any problem.


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Figure-1, Logic level values for the DRV8833 chip

The figure-2 shows the schematic diagram of the circuit. The Vcc defines the motor supply voltage. Be careful about its maximum rating which is 11.8V. As you can consider, there is no need to implement protection diodes or other extra components.

Image
Figure-2, Schematic diagram of the motor driver

The DRV8833 introduced a PWP 16-Pin HTSSOP package. For the schematic symbol, footprint and 3D model, I used the free SamacSys tools, because it is time-consuming to design the symbols and component libraries from scratch and by datasheets information.
I mainly use the Altium Designer as a CAD tool, therefore I used the Altium plugin (figure-3). Just select the PWP package which adds a ground PPAD connection under the chip. This package is thermally enhanced and probably it would increase the noise immunity of the circuit.


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Figure-3, Select the PWP package in the plugin search results

The figure-4 shows the top layer and the figure-5 shows the bottom layer of the PCB board. The capacitor C3 has a 1206 package. The connector K1 is an 8-Pin 1mm pitch FPC connector, which you should use a flat ribbon cable to connect it to your main circuit.
The connector P1 is a Molex 2.54mm pitch connector which is used to connect your motors to the PCB. The figure-6 shows a 3D view of the assembled PCB board.

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Figure-4, A top layer view of the PCB board

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Figure-5, A bottom layer view of the PCB board

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Figure-6, A 3D view of the assembled PCB board

The table-2 shows the PWM control of motor speed.

The nFault is an output active-low pin. It means in over-current or over-temperature conditions, the chip will pull it down. It is an OD (open-drain) I/O. Therefore, it is better that you pull it up with a resistor to your logic voltage (3.3V or 5V).

The NSleep is an input pin. The logic-high will activate the device and logic low (default) will bring the chip to the low power and sleep mode condition and resets all logic. This pin has been pulled-down internally.

Image
Table-2, PWM control of motor speed

References
Datasheet: http://www.ti.com/lit/ds/symlink/drv8833.pdf
Schematic Symbol, Footprint and 3D model: https://componentsearchengine.com/part. ... tID=232778
Altium Plugin: https://www.samacsys.com/altium-designe ... structions

MarkR
Posts: 152
Joined: Fri Jan 25, 2013 1:55 pm

Re: An easy to build PWM controlled DC motor driver

Tue May 07, 2019 5:34 pm

I'm not sure how it's supposed to be "easy to build" with a SMT IC which has a pitch of 0.65mm, that's pretty tricky soldering territory.

Nor is it immediately obvious how this interfaces with the Pi.

There are also approximately a zillion existing DRV8833 breakout boards available from the usual suppliers. There are also other open source designs.

(Hint: search for "drv8833 breakout")

There is also at least one drv8833 Raspberry Pi hat board which can be bought (I don't know if this is open source).

So maybe it's an interesting intellectual exercise, but it's far from the easiest option for driving motors from your Pi.

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hesam_m
Posts: 16
Joined: Thu Apr 25, 2019 9:45 am

Re: An easy to build PWM controlled DC motor driver

Fri May 10, 2019 9:58 am

it is not tricky to solder such a component at all. I can solder smaller than this, even near 0.2mm with just an ordinary iron and some flux.

Brandon92
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Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: An easy to build PWM controlled DC motor driver

Fri May 10, 2019 10:05 am

hesam_m wrote:
Fri May 10, 2019 9:58 am
it is not tricky to solder such a component at all. I can solder smaller than this, even near 0.2mm with just an ordinary iron and some flux.
I saw that you are using the chip with the exposed pad at the bottom. And it is important that that pad is also soldered correctly. Not all people have the equipment and skills to do that.

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hesam_m
Posts: 16
Joined: Thu Apr 25, 2019 9:45 am

Re: An easy to build PWM controlled DC motor driver

Mon May 13, 2019 7:17 am

Brandon92 wrote:
Fri May 10, 2019 10:05 am
hesam_m wrote:
Fri May 10, 2019 9:58 am
it is not tricky to solder such a component at all. I can solder smaller than this, even near 0.2mm with just an ordinary iron and some flux.
I saw that you are using the chip with the exposed pad at the bottom. And it is important that that pad is also soldered correctly. Not all people have the equipment and skills to do that.
Yes, but you are not bounded to use it, of course it is better in terms of thermal dissipation, but you can use a package without that exposed bottom pad. it makes no difference in the operation

That bottom ground pad soldering needs a hot air station of course (although it is cheap to buy)

Brandon92
Posts: 769
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: An easy to build PWM controlled DC motor driver

Wed May 15, 2019 2:14 pm

hesam_m wrote:
Mon May 13, 2019 7:17 am
Yes, but you are not bounded to use it, of course it is better in terms of thermal dissipation, but you can use a package without that exposed bottom pad. it makes no difference in the operation

That bottom ground pad soldering needs a hot air station of course (although it is cheap to buy)
Okay, but if you/ some else use the one with the pad on the bottum. It is necessary that it is soldered correctly, according to the datasheet. Also, when you add more vias under the chip itself (like in the example of the datasheet) you can use (read abuse) that to solder the exposed pad of the chip. By placing the solder iron on the bottom of the pcb.
But the other one is indeed eiser to solder.

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hesam_m
Posts: 16
Joined: Thu Apr 25, 2019 9:45 am

Re: An easy to build PWM controlled DC motor driver

Sat May 25, 2019 4:46 pm

Brandon92 wrote:
Wed May 15, 2019 2:14 pm
hesam_m wrote:
Mon May 13, 2019 7:17 am
Yes, but you are not bounded to use it, of course it is better in terms of thermal dissipation, but you can use a package without that exposed bottom pad. it makes no difference in the operation

That bottom ground pad soldering needs a hot air station of course (although it is cheap to buy)
Okay, but if you/ some else use the one with the pad on the bottum. It is necessary that it is soldered correctly, according to the datasheet. Also, when you add more vias under the chip itself (like in the example of the datasheet) you can use (read abuse) that to solder the exposed pad of the chip. By placing the solder iron on the bottom of the pcb.
But the other one is indeed eiser to solder.
yes of course the one without an exposed pad is easier to solder. the pinout is identical, so you can just use that one. yes, the Vias under chip can ease the soldering process from the other side.
I see some designers follow this and some do not like and just use a plane without any Via (mostly when the board is going be soldered by a pick and place machine)

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