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SimmBus Breadboard Blank Printed Circuit Board Price: ($40AUD)
Includes World Wide Postage.

Please Note **** This product is only available as a bare board. You must get your own components as specified in the parts list below:

The SimmBuss BreadBoard and Experimenter PCB Project

... click icon for PCB overlay in PDF format ... click icon for Schematic in PDF format


This project describes an experimenterís breadboard platform for developing projects or experiments using SimmSticks in conjunction with PIC or ATMEL micros. The board connects to one of the SimmStick motherboards or programmers (i.e. DT001, DT003, DT004, DT006) and incorporates the following features:-

§ Solderless Breadboard 3 ¼ " x 2 "
§ Access to the SimmStick bus via 2 x 30pin sockets next to breadboard
§ Switched and fused PWR rail from bus
§ Variable regulated power supply 0 Ė 12 volts
§ Additional +5 volt regulated supply

§ 2.5V reference voltage regulator (can be set to other voltages)

§ Negative rail voltage generator (- PWR volts)

§ 4 general purpose LED indicators

§ 2 Push Button Switches

§ 2 BCD rotary switches (4 bit)

§ Access to ALL pins of 28 and 40 pin micros using a DT106 or DT107

§ DB9 male or female test connector

Enjoy developing circuits with OpAmps, ADCs, DACs, temperature chips and most other devices without having metres of wires or cables trailing all over your bench (or kitchen table).


The SimmBuss BreadBoard kit consists of a Double Sided, through plated PCB and an overlay. All the components to build the finished project are readily sourced and may be purchased locally. A complete parts list, including suppliers part numbers for specific items is included in this document..

You can add all the components to build the complete project, or just those sections which most require. If you are using either the DT106 (PIC) or DT107 (Atmel) SimmSticks, you will also want to add the JJ1, JJ2, JJ3 connectors which will provide breadboard access to all the pins of your micro which are not accessible via the normal 30 pins of the SimmBuss. For Atmel users, a stick-on overlay is supplied to replace the silk-screened pinout on the PCB.

The photo above, shows a DT001 programmer + DT106 + SimmBuss Breadboard. This combination forms the basis of a complete development system for newcomers (and oldies alike) to the world of PIC and Atmel micros.

Circuit Details


All power for the SimmBuss BreadBoard is derived from the PWR line coming from the motherboard. This voltage should not exceed 18 vdc. If it does, the fuse (F1) may blow because of over-voltage protection zener ZD1. If this occurs, you may have to change your AC adapter (or wallwart) to a lower voltage type.

Breadboard Area

Machined Pin IC socket strips (30pin) are utilised to provide plug-in connections for the SimmStick bus on both sides of the breadboard. Two smaller 5pin strips provide access to the ground and supply rails at the bottom edge of the breadboard. Use of 0.5mm or 0.6mm wires is recommended. This is the single core wire used in telephone distribution cables so ask your local telecom installer for some scraps when you see him working near your house.

5 Volt Supply

This circuit uses a standard 78L05 regulator. Output current should be kept below 40mA. If you need more current than this,  use the 5 volt rail on the SimmStick bus if a 7805 is fitted to your motherboard.

Negative Rail Supply

This circuit uses an ICL7662 charge pump which inverts the voltage on the PWR line. This chip is similar to the ICL7660 but can have an input voltage up to 20 vdc.

Variable Voltage Supply

An LM317L provides a regulated output voltage of 0 to 12vdc which is adjustable by a 10 turn trimpot for accurate settings. The maximum output voltage will be limited by the actual voltage on the PWR line. As the dropout voltage of the 317L is about 2.5v, the maximum output voltage may be limited by the PWR voltage on your configuration.

Note that the FET Q1 and diodes D2 and D3 may be omitted, however, the minimum output voltage will then be +1.2V instead of 0v.

Voltage Reference

A reference voltage regulator based on the TL431 provides a stable voltage reference of 2.5V. Provision has been made on the board, to fit programming resistors to achieve alternate output voltages. This allows you to set up other reference voltages such as 4.096V etc. See TL431 data sheet for further details.

BCD Switches

Provision has been made for 2 x 4bit BCD switches. These can be either the 10 position type (0-9) or the 16 position type (0-F).

Leds and Switches

These have been provided for general purpose use. The leds should be low current high brightness types otherwise you may have to reduce the values of the series resistors.

DB9 Test Socket

Breadboard connectivity to either a male or female DB9 socket.

Construction Notes

a) Insert connectors J1, J2, J3, JJ1, JJ2, JJ3, and the 2 x 5pin socket strips near the bottom of the breadboard

b) Carefully remove 15 machined pin sockets from a socket strip (using side-cutting pliers), and solder these in the 15 octagonal shaped pads. These will provide connections for the LEDS, Switches etc.

c) Solder in all the resistors, capacitors,  switches, the fuse holder and RV1

d) Put a wire link in place of R19 and omit R18

e) Add the electrolytic caps, diodes, leds, semiconductors and ICís. Watch for correct orientation of these parts. It is wise to use an IC socket  for U1.

f) Insert a 5pin and  4pin piece of socket strip for the DB9 socket

g) Stick the breadboard in place using double sided tape. Most of these breadboards already have the tape fitted on the rear.

h) Attach some nice rubber feet at each corner of the PCB.

Now, have a quick rest, then check all your work (especially soldering) very carefully.

If all is well, grab your DT001 board, or one of the other DT motherboards, and plug the J1 connector into the female 30 pin connector at the back of the motherboard. If the motherboard does not have a female connector fitted, well now is a good time to fit one.

Cross fingers and turn on power to the motherboard. Flick on the switch and the PWR led should light. If not, check that you put the fuse in.


A) If the ON led lit, go to B), otherwise check the voltage coming in between PWR and GND. If this is more than 18 VDC, you may need to change your power source/plug-pack/wall wart to a lower voltage. (Or you could change ZD1 to a 20V zener, but NO HIGHER)

B) Check for 5VDC between +5 and GND on the Power Supply Connectors (at bottom of breadboard)

C) Check for a negative voltage (-PWR) between V- and GND on the Power Supply Connectors

D) Check that PWR volts appears between V+ and GND on the Power Supply Connectors

E) Check the voltage between Var and GND on the Power Supply Connectors. This voltage should vary from 0V to about 12V when turning RV1 from one extreme to the other.

F) Check the voltage between the REF terminal and GND. This should be very close to 2.50V.





Part Numbers


Aust & UK


Specific Parts


Solderless Breadboard

DSE H4035


JAM 20600


PCB Fuse Holder

RS 415-014

DK 4527K-ND



PCB header, right-angle, 30way 

DSE P2726 

RS 472-988 

DK 929835-01-36-ND


J2, J3

IC Socket Strip 30way

DSE P4300

RS 267-7416

DK ED7064-ND



7101 SPDT Toggle Sw

DSE P7654

RS 330-963



SW4, SW5

BCD Rotary Switch 

JAY SR1222

RS 665-225



SW2, SW3

Push Button Switch

DSE P7572

RS 334-915

DK EG1401-ND



10k Multi-turn Trimpot

JAY RT4650

RS 160-225

DK 3296Y-103-ND



IDC Header 40x2



DK 929836-09-36-ND


JJ2, JJ3

IC Socket Strip 30way


RS 267-7416

DK ED7064-ND

Generic Parts






ICL7662 Charge Pump Converter IC



LM78L05 Positive Voltage Regulator 5V 100mA



LM317L Adjustable Positive Voltage Regulator Low Current



TL431 Programmable Precision Reference



2N5485 or MPS102 JFET (or similar)



18V 1Watt Zener Diode


D1, D4

1N4004 Diode


D2, D3

1N914 Diode



250mA fast blow fuse M205 type



100uF 25V Electrolytic Capacitor RB



LED Red 5mm High Brightness


C2, C3, C11, C12

10uF 25V Electrolytic Capacitor RB


C4, C5, C6, C7, C8, C9, C10

100nF 50V Monolithic Capacitor


R1, R2, R3, R4, R17

1k0 Resistor 0.25W


R5, R6, R7, R8, R9, R10, R11, R12, R13, R14

47k Resistor 0.25W


R15, R16

3k3 Resistor 0.25W


DB9 Male or Female Connector (standard solder type)

Supplier Codes:

DSE Dick Smith Electronics

JAY Jaycar Electronics

RS RS Components

MAP Maplin

JAM Jameco

DK Digi-Key

Additional Notes:

1) The part numbers specified have been derived from suppliers lists and catalogues published on the Web. Please verify correctness and suitability for use before purchasing.

2) Should you have difficulty purchasing the specified fuse holder (Keystone Electronics #4527), you can replace this with M205 PCB fuse clips which are commonly available. Spare holes have been provided on the PCB to accommodate these.

3) The specified BCD switches are 10 position (0 to 9) units. However, 16 position switches (0 to F) are also available and may be substituted.

The Printed Circuit Board for this project is ONLY available from DONTRONICS.

Project designed by : Wolfgang MaierSCORPIA DESIGNBrisbane,  AUSTRALIA


Contact me :   w.maier at qut.edu.au

Trademarks:                            SimmStick is a trademark of Dontronics

Wolfgang 6-Feb-2002

1) The right-angled pin header is wrong DSE part No. DSE do not seem to
have a RA header. Don's part is suitable simcon.html

2) the 7662 and TL431 are both available from FARNELL.

ICL7662CPA      Farnell # 408-610       AU $5.71
TL431CLP        Farnell # 411-838       AU $2.03

Contact Farnell (Australia) on 1300 361 005

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