Attempt to fit a quadcopter in a 5x5cm PCB

[erdabyz]

This is something I've been working on these days. The other day I was thinking about what would be the coolest possible thing you could fit in a 50x50mm 2 sides PCB. How about a quadcopter?

I'm aware that miniquadcopters have already been done but I'm not sure if anyone has tried to fit one in such a small size. I've tried to design one that would fit. It's powered by a PIC32 and it uses a MPU-6050 as the inertial sensor, which will implement the motion-apps firmware inside to offload the main processor from motion fusion algorithms. I've thrown in a MAX1555 as battery charger via a microUSB port which will also be used to program the PIC via bootloader, as no ICSP pins are available. The PIC will have to be programed with the bootloader before soldering. I'll figure out how to do that. It also has a MPL3115A2 precission altimeter/barometer for altitude control and a TPS63031 as the main switchmode buck-boost regulator for everything but the motors (maybe overkill, but I couldn't find anything smaller). It will use 4mm coreless tail motors and propellers from SYMA S107 helicopters. Maybe that won't be powerful enough and bigger motors will be required, who knows. Each motor features an independent integrated H-bridge from Texas Instruments (DRV8837). Surely I could have just used a discrete mosfet per motor, but I didn't want to prematurely limit the capabilities of the thing. Maybe it turns out powerful enough to perform backflips and fly inverted, and motor direction control would be required for that. It uses a cheap HC-05 serial to bluetooth module for communications. Other radio options were thought and I don't fear RF desings, but I just wanted to keep things simple for now on that side.

As always here's the board and schematics. Schematic is crappily laid out, but I've tried my best to route the PCB. Beore you say it, I'm aware that the 22uF capacitors are placed in one of the worst possible spots and that they will likely break or crack sooner than later. We'll see. I've also checked that the microUSB connectors can indeed be soldered.

microquad.zip

(98.84 KiB) Downloaded 379 times

Don't expect too many updates on this one, but I'll tell you and provide code if it finally works. For now boards and components have been ordered. First prototype will be built in about 15 days and firmware development will start at some time. The question here is will they fly? Only time will tell!.

[katjap]

I don't feel remotely qualified to comment on a quadcopter design, but it looks like an interesting project!

[Elpis]

It's a really nice project!!!

[Markus Gritsch]

This is amazing! Keep up this awesome work.

I would really prefer to have some kind of ICSP pins/holes/pads on the PCB: 1) programming the bootloader before soldering the PIC32 is cumbersome. 2) Development of the firmware without debugging capability is really a pain.

If PCB real estate is a concern: I used some small custom 50 mil spaced pin headers, which work fine and don't take much space on the PCB.

[erdabyz]

This is amazing! Keep up this awesome work.

I would really prefer to have some kind of ICSP pins/holes/pads on the PCB: 1) programming the bootloader before soldering the PIC32 is cumbersome. 2) Development of the firmware without debugging capability is really a pain.

If PCB real estate is a concern: I used some small custom 50 mil spaced pin headers, which work fine and don't take much space on the PCB.

There are SSOP28 sockets available for relatively cheap if it turns out to be required. I have had success in the past programming PIC's before soldering by holding them against an adaptor PCB with the required footprint. I know that ICSP for PIC32's uses faster communication and its much more sentive to bad or poor connections but well, I'll try. Yeah, no debugging is also a pain but I hope that sending traces over the serial link will be enough. I also have PIC32 boards to try and debug parts of the code if required.

The problem isn't space but lack of pins. I have used every single I/O of the PIC32 and I couldn't break out ICSP1 pins as I had to use these for the serial interface. I could use them to program the thing before soldering the bluetooth module if that's required. I struggled a lot of time with the remappable pins configuration to get the easiest layout without interfering peripherals.

I also had to use a SSOP28 version of the PIC32. Smaller packages with more pins are available and I don't fear them at all. It's just that power and ground couldn't be properly routed with a leadless package with exposed pad in a 2-layer PCB. And grounding in this case MUST be properly done. We have RF, sensitive sensors, a fast microcontroller and 4 motors. Improper grounding would be devastating.

If this turns out to work, next revision will have a 4 layer PCB, a PIC32 with more pins and a different type of radio integrated in the PCB that would allow easy network communications. The final goal is to build a lot of these and make them collectively fly. I'm working at the RF group of my university and we're planning on designing a full-featured MIMO testbench and one of the likely applications would be radio-based localization. If everything works we could maybe use that equipment to localize microquadcopters in 3D space and make them do cool things. I'm aware that all this has already been done but our approach would cost much less money.

But well, for that to happen a lot of time will have to pass and a lot of work will have to be done. For now this is just the result of me thinking about cool ways to fill a 5x5cm board.

[Markus Gritsch]

I see. Maybe you could have opted for the non-USB version PIC32MX130 to have more IO pins and use the USB connector only for charging. Although then the firmware could only be updated with a PICkit 3.

BTW, the HID bootloader takes quite some amount of flash, so you might have little left for your firmware. Maybe the PIC32MX250 is better suited.

Anyways, very cool project. Looking forward to updates from you :)

[Sjaak]

NIce project. I recently picked up a ready made quadropter for about 25$.

It has reasonable moters, a 250mAh lipo and a wireless remote. All the markings on the major ICs are sanded off. Didn't have much time to check it out, but will do hopefully soon. THe idea is to replace the controllerboard and redesign it totally.

[erdabyz]

I see. Maybe you could have opted for the non-USB version PIC32MX130 to have more IO pins and use the USB connector only for charging. Although then the firmware could only be updated with a PICkit 3.

BTW, the HID bootloader takes quite some amount of flash, so you might have little left for your firmware. Maybe the PIC32MX250 is better suited.

Anyways, very cool project. Looking forward to updates from you :)

Damn it, without optimizations it takes 43% of my flash (I'm actually using PIC32MX220F032B because neither F128 nor F64 were readily available at distributors). Hopefully the 60 days trial of optimizations makes it slimmer. If not i'll have to sample some F128's.

[Elpis]

NIce project. I recently picked up a ready made quadropter for about 25$

25$!!! Really!!! May I have a link please...

[matseng]

NIce project. I recently picked up a ready made quadropter for about 25$

25$!!! Really!!! May I have a link please...

$20 (+ $16 shipping if outside USA) - http://r.ebay.com/Lpybmq

[Sjaak]

That is the one I bought. Different colors though.

If I read the advertisement correcty that one is broken and only usable for parts.

[matseng]

That is the one I bought. Different colors though.

If I read the advertisement correcty that one is broken and only usable for parts.

True... Somehow I failed to notice the huge red text stating that. It should have been blinking as well for me to see it :-)

[Sjaak]

That is the one I bought. Different colors though.

If I read the advertisement correcty that one is broken and only usable for parts.

True... Somehow I failed to notice the huge red text stating that. It should have been blinking as well for me to see it :-)

Did you tell the seller? :P

[bearmos]

This looks like a really fun project, erdabyz!

It will use 4mm coreless tail motors and propellers from SYMA S107 helicopters. Maybe that won't be powerful enough and bigger motors will be required, who knows. Each motor features an independent integrated H-bridge from Texas Instruments (DRV8837)

I have a re-branded SYMA S107 and the tail motor is pretty wimpy (good for its size/weight, but still doesn't provide a lot of thrust). The tail motor also burned out after a few dozen flights. If you have them laying around and are sampling most of the other parts, go for it. But, if you need to buy them, I would go for something with a bit more oomph:). Now, the main rotor motors are a different story entirely (each copter has two). They are bigger and would require much more current at full power, but should give you more than enough power. Weight vs thrust isn't something I have a lot of experience with - so take all this for what it's worth (probably not much)...

[Aeroengineer1]

I can state that the DRV8837 are nice little parts and easy to use. I am using one right now in my current project. They are light and small. The Rds-on is a bit higher than what I would like, but when you need the smallest part available to drive 1.8A in forward and reverse, this is it.

Adam