STM32F4

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Animabot Rev3 – Mecha – Head Assembly

Posted by Emmanuel Sichet on 11/11/2019
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Now it is time for the head assembly, as always, this is kind of a headache because of all the tiny parts and dimensions… I started by mounting the eyes (OLED PCB) with the 5Mpx camera (between the eyes). The PCB is screwed in place. Then I continued with the gesture sensor with is directly glued, I couldn’t used screws due to the thin thickness of the head and the lack of space !

Eyes and Gesture sensor
OLED Eyes
Head inner side

Then, followed the servos of the ears, this step was pretty straightforward. Place the motors and screw them 😉 As you can see, there is not so much space for adjustment…

Servos Ears
Servos Ears

The most complicated part was to install the neck servos, due again to the small space, it was quite hard to fit all together with screws, bearings and cables… I had to make custom horns and spacers to fit everything in place. The overall tolerance I had to place the servos was exactly 1mm, and it took me a complete morning to assemble the head properly but that is the price for compactness.

Pitch servo assembly
Neck, bottom view
Neck, Top view

After mounting the neck onto its head, it was time to test if all was working as expected (I2C for the eyes and camera) and thankfully, it does :D. All the cables passe through the back of the neck for a rotation of about +- 60°. However, I have some doubts about the head connection to the yaw servo, I find it a bit weak and wobbly… I guess I will have to find a way to make it more robust.

All good !
Head complete
Ready to connect
Head bottom
Servo for Yaw movement
Head-Body connection

The last part to assemble is the Top Cover, containing the Raspberry Pi, audio amplifier, speakers, the Hood and the tactile switch…

Animabot Rev3 – Hardware – Motherboard Update (Final?)

Posted by Emmanuel Sichet on 05/11/2019
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After weeks of testing and debugging, I think that the motherboard is finally ready 😀 I had some trouble with the charger which wasn’t communicating nor charging… The reason was simply a bloody wrong capacitor value…. but now it is fixed and working like a charm !

I also discovered some issues on the Servos power supply. Basically, it was not regulating well and completely not handling any load… So, I fixed that as well and did some extensive tests. Now, I’m proud to announce that the power supply has been tested with a continuous load of 16A at 7.6V (8A per channel) for 1 hour without any issue ! the temperature didn’t exceed 60°C (without fan).

So now that all errors are solved, I installed the motherboard where it belongs, and here are the results :

All populated !
Servo Power Supply (LM25119)
Battery Charger (LTC4015)
Motherboard installed
Power Connectors
Assembly Overview

 

Animabot Rev3 – Hardware – Motherboard Update

Posted by Emmanuel Sichet on 06/09/2019
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The first version of the hardware was a very good start, I could use and verify many components and features. However, I found many bugs and improvements here and there were necessary !

The first problem was the bandwidth used by the 2 OLEDS for the eyes. In order to have fast and smooth transitions on both display I boosted the bus clock from 400kHz to 800kHz. I know that normally the I2C high speed is 400kHz but from an article I read on HackaDay, the SSD1306 doesn’t actually need the ack to process the command from what I remember…  Obviously the other sensors cannot follow that speed, that’s why I use now two I2C bus: one for the Eyes, the other for the rest of the sensors.

The second problem was the JTAG connector right under the TopCover bottom base, so the cover couldn’t fit properly…

After some servos tests, I discovered to my surprise that when given a PWM, they are always making noise ! These servos are meant for Helicopters so I guess regarding the huge copter noise this is not disturbing… but for my purpose it is ! So after many test of PWM and software tricks I decided that the most efficient way was to add am MOSFET to the servos power supply. With this solution I only power the servo when they need to move, the rest of the time they are OFF (which is also good for power consumption)

I also improved the cooling of the main PSU by adding thermal pads beneath the MOSFETs and by adding a “venturi hole”. The wind tunnel uses a radial fan just on top of the PSU, but as it is a radial , it blows air directly towards the tunnel output. As the area below the fan is closed, all the sucked air goes directly out and there is a “hot air pocket” below it. By adding a hole beneath, the air is also sucked form the bottom of the PCB and flows through the component this time !

I decided to get rid of the 10DOF IMU board… it was too bulky and after consideration I do not need a barometer neither a compass. The accelerometer and gyro are just what I need for stabilization, the rest would be gadget… So, I looked up a bit an found a nice inertial module from ST, the LSM9DS1. Yes, it has a compass, but I will not use it.

Concerning the 5V power supply, I still don’t know why it burned when I connected the battery, because the schematic and layout are correct, and when it burned, the use case was within the range of the component,. So it will require further investigation and hopefully it won’t happen again !

Last but not least, I redesigned the power management, which allows a smart shutdown from the MCU instead of the switch, which gives me more flexibility and control. So basically, when you flip the switch ON, it enables the 3V3 of the MCU. Then the MCU has control over the 5V and 9V of the motors with dedicated EN pins  and via a general switch (MOSFET). When I want to shutdown the robot, I flip the switch OFF, this info is transmitted to the MCU and after a predefined timeout the robot will prepare its shutdown, move to its Park position then switch OFF completely (no current draw at all !)

Top Side
Bottom Side

The white thing you see on the bottom side is the NTC of the battery charger. I mounted it on strap which serves as a spring to press the NTC against the battery for temperature control 😉

Animabot Rev3 – Mecha – Upper Body Assembly

Posted by Emmanuel Sichet on 15/08/2019
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After the Lower part, the Upper body was the logical next step. Actually, there was not much to do on this one… I started by installing the insert for the Top Cover, using the same method as before, which went flawlessly…

M2.5 Inserts
Top side
Bottom side

After the inserts, only the Flexible OLED display was left to install. I placed it first to see how the active area will match the outline of the body,then, I simply added double sided tape on the inner frame and pressed it against. In order to protect it, I added some felt tape and it looks nicer as well 🙂

For the cable, I first wanted to use braided sleeve but it turned out to be too rigid on the connectors and bit tricky to do… so I opted for the automotive solution by wrapping the cable in automotive tape. This looks pretty neat and avoid rattling noise if the cable is moving against the body.

OLED placement
Mounting
Outside view

And voila! The result turned out to be much better than I thought, this curved display looks stunning ! I can’t wait to make a proper HMI and menus 🙂

Animabot´’s Logo
Some sensors values
Animabot´’s Logo

See you later for the Top Cover assembly !

Animabot Rev3 – Hardware – Motherboard

Posted by Emmanuel Sichet on 27/07/2019
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I finally received the rest of the components for the motherboard ! took me some hours to populate everything (QFN packages take a bit of time to solder when you are not used to 😀 )The smoke test passed for the Power supplies (7.6V, 5V) but I still have to test the battery charger… which gives me a bit of apprehensions because I don’t want to fry my battery :/

I will definitely have to make an improved version in the next few weeks to fix the following issues:

  1. Lack of thermal exchange for the PSU controller and MOSFET
  2. Change from 10DOF IMU board to a 9DOF IMU (LSM9DS1TR)
  3. Separate I2C bus for the Eyes (they use too much bandwidth forth rest of the sensors)
  4. Overall Routing & Layout improvements
  5. More detailled SilkScreen

But first I have to finish testing all the features and components to see if further modifications are required. But for now I’m pretty happy with the result, no big trouble. I did some thermal test and the PSU is around 40°C in idle mode without cooling and 35°C when the fan is active, even so the thermal dissipation of the component in not ideal and the fan is powered at 3V3 instead of 5V.

Motherboard in progress

As mentioned, I still have the rest of the features to test (around 15: Telemeter, Bluetooth, Charger, Raspberry Pi communication, Servos, etc…) so stay tune 🙂

Animabot Rev3 – Hardware – Motherboard

Posted by Emmanuel Sichet on 29/05/2019
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So I received the Motherboard and started populating it 🙂 All components are not yet soldered because I want to test the board step by step, starting with the MCU and the I2C bus (where all the sensors are connected).

Motherboard test

As of now, the following is working:

  • Flashing-Debugging the MCU
  • Flexible OLED via SPI
  • 10DOF IMU via I2C
  • Eyes via I2C
  • Gesture Module

I still have some trouble with the RTOS and the IMU, after some time the tasks start to be delayed and the IMU is not responding anymore… but that will be for later, I want to finish the Body design and send it for printing first ! the next step is to mount the PSU and the Charger.

But now that I have the Eyes working I started implementing some expressions 😉 not so bad for a first try !

Animabot Rev2 – Final Assembly !

Posted by Emmanuel Sichet on 04/11/2015
Posted in: Animabot Rev2. Tagged: , , , , , , . 2 Comments

It’s been a while since the last post… mostly because my new job is taking away most of my time…

But also because I had to fix several issues in Anima before mounting the legs and the upper body. First I had to fix the sound problem, curiously the IR sensor was generating noise which was propagated up to the audio amplifier, thus generating audible noise… To fix it I added to capacitors (100nF & 10µF) on the sensor’s power connection. Then I burned the Li-ion charger 😦 so I had to replace some mosfet and add some heatsinks.

Finally after 20 months of design, tests, doubts, bug fix, etc… Animabot is assembled and ready to walk !!!

 

Stay tuned 😉

Animabot Rev2 – Body Assembly (part 3)

Posted by Emmanuel Sichet on 03/09/2015
Posted in: Animabot Rev2. Tagged: , , , , , . 2 Comments

Hello ! The assembly of Animabot is going well, I have almost finished 🙂 I’m mostly making cables and cables… Thinking about how I’m gonna put all of them into the body… But anyway, I’m also testing the electronic and everything is also fine up to now: Audio amp and speakers, IR telemeter, fan, Night LED, temperature sensor and power monitor and the ATX Raspi are working !!!

The Rapsi is also much thinner without all these big connectors 🙂 but I have some issues with  the WIFI dongle and I need to test the webcam.

So I put all the parts together to see if all goes well, and for now it’s look like this :

Power ON baby !

I like it ! even if the parts are not perfect as I would like, and even if the design is full of errors, it doesn’t look so bad 🙂

More update soon 😉

Animabot Rev2 – Boards programming

Posted by Emmanuel Sichet on 05/02/2015
Posted in: Animabot Rev2. Tagged: , , , , . 9 Comments

Hey, It’s been a long time since I posted news on Animabot 😉 I didn’t advanced much on the software but I can now talk to the servos which is a very good news 🙂 I still have to make all the functions to control them correctly (setPosition, getPosition, moveAll, setTorque, getTemp, etc.) but it will be more interesting !

I’m still waiting for my 3D printer… and it begins to annoy me…

Servos are alive !
Servos are alive !
STM32F4 under programming