The electronics review

Here is the main board schematic.

As it can see, is based on a ATMEGA64. The board has four L298, each of them has two full transistors bridges. Two of them manage the two stepper motors and with the other two it can manage up to four CC motors. The board has also a LCD connector were I have connected a 16x2 display. It has also some tension dividers to adapt the signals going to the ADC converters. I'm using two ADC converters to measure the arm angles trough a potentiometers and a third channel to measure the battery voltage. The hardware is also ready to measure the current consumption of the motors.

The board has a 40 pins connector were there are the ADC inputs, the motors, I2C to connect two ultrasound sensors and some general propose pins connected to the microcontroller. I have used 3 of these pins to put a encoder and measure the hand position.

The board has also three leds. To program I added a SPI connector, but when I tried to program the fuse bit the first time I failed and then it didn't work. Finally, I bought a JTAG programmer and I soldered some wires to the board to put the JTAG connector

Here is also the PCB design. The design has two layers.

Here is a photo of the board working. The board is hand made done, using a two layers board with a photo sensible material. The process to do it is print the photolytic in a transparent sheet, then you have to isolate the board in both layers, put it in a revealing and finally put it in an acid to remove the spare copper.

When I made the board, the first I did was to solder the main components to do it work like the microcontroller, oscillator, programming connector... Then I made a simple program to turn on the led and I programmed it. The picture was made after I performed the LCD driver and as it can see most of the components are not mounted.

In the next entrance I write about the programming environment, tools and how I did to program it. If you want more information, you want the schematic or whatever you need don’t hesitate to contact me.