New June 2006 HB system with removable serial/usb connector

HB 08M Board - original requirement

The design of the home brew ( HB) board arose from many student projects with the PICAXE 08M series of devices.  A need was expressed for a simple modular design that would introduce all the functions of the device and permit reliable interconnection.

The system would serve as a teaching system that could be extended by students in their own projects.

The design is based on the artwork supplied with the Picaxe programming system but has been extended to:

a) 10 position female connector that prevents static damage to pins

b) Diode to prevent reverse polarity damage to the device

c) Simple design undertaken with Techsoft PCB Design and make

d) Jumper connector with same annotation as pins on the device rather than “legs).

Changes in June 2006

Voltage regulator added to design

Modular programming to allow USB or SERIAL programming

External power supply option of HB2 Servo board

HB3 changed to permit external SWITCH or INFRA red in.

HB 08M Board Changes in June 2006

Extra points were addressed during the first year of operation of the HB series. Many teachers were worried about the possible damage to the O8 if a 9V battery could be accidently connected to the connector.

Also, many schools had purchased laptops with USB ports and USB connectors were needed in the classroom. We had also run about 4 training courses in schools and flat batteries, lack of power supplies and general problems opened the way to a new USB adapter that also supplies power to the main board and also shows the status of the receive and transmit lines. This was seen as a major improvement over conventional USB adapters.

A more modular approach was planned as well as taking account of student activities where it was seen that making and soldering three sets of boards AND the microcontroller was not a good design activity.

Many schools are using the HB series as a teaching introduction and a platform for expansion and students designs.

School investment in these boards are preserved because the new advanced ATMEL FLASH SYSTEM connects to the HB1, HB2 and HB3 boards.

HB 08M Board Schematics

The following figures are the maps or schematics of the HB main board. The schematics have been divided into sections but you can download the whole PDF of the board.

Note that the connections from the PICAXE-08M U1 component are labelled as PIN4 etc. It is difficult to label the pins as IN4 etc because the pins have a multiplicity of functions.

The PIN3,4,5,6 and 7 nets ( or lines) are connected to the black connector that serves to link to other modules.

HB 08M Board Functions

JP1 - 5x2 pin Box header for serial/USB connector

J3 - two pin connector to allow 5V from the external USB connector

U1 - Picaxe 08M microcontroller

C1, 100nF ceramic bypass capacitor

HB 08M Board Expansion

The large, black female connector serves to connect the HB 08 microcontroller to other expansion boards. Again, the design was chosen for robustness in the education area. It is impossible to short the connections.

Note that the labels on the connectors are PIN7_08M. This nomenclature was chosen to set up some standard when other microcontrollers are designed.

HB 08M Serial connector

The box header allows either a serial board or the USB board to connect to the computer for downloading of programs.

A separate system was chosen to make it easy to connect two systems. Also, some schools have designed a DB9 connector to fit onto the serial board and then use low cost serial cables available from most electronics suppliers.

Alternatively, power is derived from the USB bus when connector J3 has a shorting  link placed over it.