- Connectors for Freescale FRDM-KL25Z board (or any other dual row FRDM board, e.g. FRDM-KL46Z).
- Connectors for Pololu modules (motor driver, DC/DC converters, reflectance sensor array, quadrature position encoders).
- 2 micro-metal DC gear motors from Pololu, using the Pololu Zumo chassis and blade.
- Powered by 4 AA batteries, with reverse voltage protection and protection against short cuts.
- I2C sensor connector and up to four digital sensors (e.g. for object detection).
- Connector for ultrasonic distance sensing module.
- User LED and push button.
- Wireless Connectivity: IEEE802.15.4, Bluetooth or 2.4 GHz module from Nordic Semiconductor.
So far two PCB’s are getting populated and tested. Below is one PCB with SMD components populated:
Next, with most connectors added. Distance headers are added to increase the distance between the base board and the FRDM board:
Then, the FRDM-KL25Z (or any other FRDM board) is placed/connected on top of it:
The result will look similar to this (picture below shows the prototype base board):
In above picture, the green Freescale IEEE802.15.4 transceiver card is not connected yet, as it needs a small adapter PCB.
Next week all the other components get populated, assembled and tested. Already identified a small problem with the connection to the IEEE802.15.4 transceiver connection: the connector for it is too close to the connector for the FRDM board. But this problem can be easily (mechanically) solved. Additionally, the FRDM board cannot be easily removed due the friction of the dual header rows (still thinking about a better solution).
I have received several questions/requests if they could get a board/robot. Simple answer: yes, if you register for my class :mrgreen:.
But this triggeredd some thinking about the next iteration. With the current batch of 40 robots/PCB’s, the budgetary costs for a single robot are:
- US$ 20: Base PCB (dual layer, silk screen, including initial setup costs)
- US$ 20: Components (headers, resistors, buttons, LED’s, …)
- US$ 110: Pololu components (Zumo chassis, two DC motors, motor driver, two DC/DC converters, two quadrature encoders, line sensor, Zumo blade)
- US$15: FRDM-KL25Z Board
- nRF24L01 transceiver (US$2.75) and/or Bluetooth module (around US$6), ultrasonic module (around US$3.00) and added digital or I2C sensors.
So makes around US$150 without the FRDM Board/transceivers/extra sensors. The board features connectors for a serial-to-USB Bluetooth module and the nRF24L01+. The most expensive parts are the motors and the quadrature encoders. The DC/DC converters, motor driver and quadrature encoders could be integrated on the PCB to reduce costs. Additionally, we are looking into having the boards produced with all the SMD components already populated. That would it make it really easy to build your own robot.
Of course everything is about quantities. If there would be enough demand, I think a robot could be possible for US$100? But would there be enough demand for such a robot? I you want to have a closer look: On GitHub I have published the Eagle files, schematics and an initial version of the assembly guide.
Let me know what you think and post a comment to let me know if you are interested in participating. Then this could lead to a KickStarter or similar project :-)?