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:
- Lack of thermal exchange for the PSU controller and MOSFET
- Change from 10DOF IMU board to a 9DOF IMU (LSM9DS1TR)
- Separate I2C bus for the Eyes (they use too much bandwidth forth rest of the sensors)
- Overall Routing & Layout improvements
- 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 🙂
A small update about the boards, as you can see on the photo below, the boards are connected together and the power is well-distributed in each of them.
I have also set up my software environment using Eclipse and ChibiOS RTOS. I can now working on the STM32 configuration and mid-level implementation for ADC, SPI, LTC2945, Sensors (Temp, IR, accelerometer) etc… The Serial Driver is already working so I can at least use printf for debugging 🙂
As I’m still waiting for my 3D printer, So I concentrate of the software and I will continue the mechanic later.
I finally received my boards \o/ I spent my week soldering them and here is the result:
I prefer this new version to the old one, the top silk is also better. I didn’t performed all the tests yet, but at least the “smoke test” passed !
The next step is to interconnect them and see if everything is alright. Once I will be able to control one servomotor, a big step will have been made.
The next week I think I will have finally finished the 3D design; I will post the finals renderings.
Keep in touch 😉
Hi everyone ! I just come back from holidays and I have received my electronic boards \o/ (made on SeeedStudio)
I also received some cables and the new speakers. I hope I will have time this week to solder the boards.
There are some problems with the top Silkscreen (some letters are missing) but the tracks are good and the quality is also very good. I think the problem comes from the gerber export which gone wrong at some point…
The Raspberry is finally installed ! I just bought the model B+ because it has 4 USB ports, and as I will need 2 for the Wifi and the Webcam, I needed 2 more for the keyboard and mousse for programming the PI 🙂
The model B+ has also 4 mounting holes, which is perfect pour the fixations and it consumes less than the previous model (around 150mA). However I will need to replace the USB and Ethernet connectors which don’t fit in the hood by pin row connectors 😉
I also mounted the mini USB of the STM32 on the top, which is much more easier for programming…
Now I can continue with the final step : The head
I finally finished the integration of the boards inside the body ! It took a little more time than I thought but I wanted the most reliable solution.
For the fixation I will use a carbon fiber support (which I will machine with my CNC). This support will also reinforce the body’s structure 😉 and so far, everything is fitting well inside so I hope it will be the same for the head…
However, I still have to integrate the Raspebby Pi, which will be placed above the STM32.
Rear view with STM32
Top view with STM32
Side cut view
So, the next step is to put the Pi inside and then begin the head design.
I spent the last week on the electronic design. I finished all the boards except the one for the Pi. All the schematics and PCBs are made on Altium Designer.
I also received all the components \o/ so now I can check a last time that all the footprints are correct.
The next step is to send the gerber files of the boards for manufacturing. I’m hesitating between 2 manufacturers : OSH Park and Seeed Studio PCB. I think I will go with OSH Park (previously Batch PCB) because they have a better quality even if they are a bit more expensive than Seeed Studio PCB.
Now I have the boards, I can continue the work on the integration of the boards into the robot and the design of the head.
I didn’t advanced much on the Solidworks Design because I need the size and shape of the PCBs I have to integrate…
Animabot will be composed of 5 PCBs in addition to the Raspberry Pi and the STM32 :
- Power Supply Board
- Li-Ion Charger
- STM32 Board Adapter
- Raspberry Pi Board Adapter
I’m using Altium Designer for the Electronic design, I know that it is a complicated software for the boards I have to do, but I am used to it (I used it previously with my first Hexapod and at my school). For the moment I’m spending a lot of time creating the components and footprints I have… so not very funny…
However, I will create the 4 others PCBs in the next few days to be able to put them into Animabot.
Top PCB View
Front IR view
I also put an Infrared sensor on the front of the robot, so he will be able to avoid falling in the stairways or from a table 😉
I reviewed the power distribution of the robot and the system of 2 batteries… and finally, I’m not satisfied… Having 2 batteries inside take more space, it’s not good for the weight balance and it’s more complicated for the electronic because I would have have to design a board with 2 chargers (LTC4008 and MCP73861) and 2 power monitors (LTC2945). It’s not that complicated but designing a charger board is not obvious and the Electromagnetic compatibility (EMC) would be a nightmare…
So I searched on the Internet for a new battery, and I found this one : Tenergy Li-Ion 18650 11.1V 7800mAh. I could have assembled the battery by myself by buying each element separately which is much more cheaper, but I have enough work to do… 😉
There are many benefits :
- Battery’s weight better balanced,
- Space better distributed,
- One charger and one power monitor,
- More capacity than with the 2 others,
- The battery case is reinforcing the rigidity of the body.
It looks like this once integrated :
New battery integrated
I logically changed the charger and chosen a LTC4006 which fit perfectly to my application. Indeed, the LTC4008 doesn’t have a integrated termination charge like the 4006 and the use case of the robot (charging point of view) will be the same as a laptop, so I needed a charger compatible for this utilization.On the datasheet you can find a good application schema, which I have to modify to fit my expectations in order to handle the average 5-6A consumed by the robot…
However, I’m still keeping my
precious switching regulators :
- 1 PTN78060WAH : 5V power supply of the RasPi, the STM32 and the speaker’s amplifier.
- 1 PTN78060WAH : 3V night vision LED (+ mini fan).
- 3 PTN78020WAH : 7.4V legs power supply : 1 for each pair of leg (front +head, middle, rear).
I replaced the PTN04050C by the PTN78060WAH (boost converter), as I won’t use the 3.7V Li-Po battery anymore.
Here is the new electrical architecture :
Electrical Architecture Rev2
The electronic is based on a PIC32 from Microchip.
I made all the schematic and the layout on Altium and then, I made the board on BatchPCB which has changed to OSH Park. The quality is very good and the price quite low (around 50$ for this board)
The mother board is composed of :
Board preview in Altium
There is also a power board composed of 3 step-down integrated switching regulators (ISR) 1 PTR08100W for the legs power and 2 PTN78060W, 1 for the head, and one the 5v supply of the motherboard
And how it looks like both boards connected :
MotherBoard and Power Board integrated
MotherBoard and Power Board integrated
MotherBoard and Power Board integrated
Animabot is equipped with 2 infrared sensors GP2D12 (front and rear), and 18 servomotors Hitec HS311 connected to the motherboard.