Build an electronic workbench tools part-1

ELECTRONIC WORKBENCH

A. PREFACE 

        One of the most important device for the hobbyist is a bread board. Bread board make it easy to wiring  circuit or to break it up again without the need to solder the components. This topic will cover about how to make some tools to attached to bread board, and this device will make our works better. For this purpose we will call this device as electronic workbench (ewb). In my opinion, the less tools on the working desk is the very good things, because the more tools on the desk will make our mind become dizzy and not concentrate to the circuit that we want to make.

        The tools that we want to accompany to ewb are the simple test devices and power supply. The test devices will be build also not a sophisticated ones, and maybe already there somewhere in your junk box. I never try to make the sophisticated tool with using hard to find parts at the market. So I put the circuits that I already made some times ago and usually already throw to the junk box. It is better to used it again, for recycle and the important purpose. If you don't have circuits like these, you may make a new one. The tools ie :

1. Power Supply : this device is absolutely necessary for making some experiment later on. Here I choose 3 pairs of power supply ususally used, ie; +/-5V (for TTL circuits), +/-12V (for CMOS circuits) and the variable one (adjustable) up to +/-30V (this is for analog circuits). 
   
   
2. Mini Amplifier : a small mini amplifier, and using popular IC, preserved for 2 type of  designs and both already tried, quiet the same. This amplifier also can used for locating the existing audio signal (frequency) range. 
   
   
3. Signal Generator : a simple signal generator, using popular IC 555 Timer, configured as multivibrator, and the parts was chosen for the audio frequency range (20Hz ~ 20kHz). 
   
   
4. Logic Probe : a simple logic tester, using 7-segmen display. This tool can be used to show 3 state of logic, ie: "L" for low logic, "H" for high logic and blinking "8" for clock logic. 
   
   
5. 8-Bits Indicator : this circuit show the logic up to 8-bit. So we could indicate the state logic from signals, eg : data signals, address signals, etc. 
   
   
6. Connector DB-25 and DB-9 : the popular type connectors for using with interface circuits to or from computer. There both are standard for LPT paralel port and serial COM port connectors. Besides that we can use it for our experiment circuits with microcontroller later on.

        That's the tools which I think most needed untill now, and not necessary need to much fund, but quiet good enough for experiments and for amateur hobbyists.

B. SCHEMATIC 

        Over all the circuits for this ewb is like this :

Usually, positive power supply often to be used, but for the negative seldom, so for you who don't need it, can be omitted, but infact that it would be need one day. For mini amplifier, you can use ex radio amplifier or from ex active computer speaker not used anymore. The pupose is depend on the needs. It can be used for tracing the signal. Signal generator needs in experiment to produce some pulses or as oscillator. Logic probe needs to detected logic state from digital circuits. 8-bit indicator usually used for detected visual logic state from many signals, if you want to compare the logic states.

        In the implemented to the ewb device, these tools connected to terminals which I use the very simple way,  using good quality IC sockets, so it would be compatible with bread board working. Pin descriptions used like this :

Power Supply terminals pun on the left side and for the other tools pun on the right side. More detail can be seen at construction section. It is more wisely to print this picture and put it on the back cover ewb box, so if we forgot the terminal purpose, we can refer to this picture.

C. LAYOUT 

        Here I already design PCBs for each tools and the last choice depends on your decision to make it with this pcb layout or use some thing else, like veroboard, or direct connection (rat nest). Infact that for my prototype, because for some tools already made before, so the picture prototype not the same with this design. Some PCBs layout not tried yet, please check it by yourself again if you want to use it. Here are these PCBs layout :  

PCBs  Layout Design