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Datasheets : PCB Wizard
The files for the various units were drawn using Livewire and can be downloaded, opened using PCB Wizard, combined to build up a complete circuit and converted to a PCB. Suppose, for example, that the system planned is a night light – a lamp should light when it is dark. A suitable block diagram might be:
The signal from the Light sensor will go low when it is dark, so the signal from the Inverter will go high, which will switch on the Darlington driver and the Bulb will light. Read the data sheets for the planned subsystems and make sure they will work as planned. In the case of the present system, looking at the data sheet for the Light sensor we find that we can simplify the circuit by using a Dark sensor, and missing out the Inverter:
If all looks well, download the Livewire files for each of the subsystems and store them on disk. You will build up a complete circuit by copying and pasting circuits for subsystems. Open PCB Wizard and save a new blank file where you will build up your complete circuit. To paste the first subsystem circuit into this, click on File > Open and change the file type to Livewire. Open the file for the first subsystem (the Dark sensor in this case).
To copy this file into your new file for your complete circuit, click on Edit > Select All (or Ctrl + A) and then Edit > Copy (or Ctrl + C). Close the subsystem file and use Edit > Paste (or Ctrl + V) to paste the first subsystem into your new circuit file. You can move the subsystem around with the mouse and click when it is in a suitable position. Do the same with the next subsystem – the Darlington driver in this example. Move it around so that the power supply rails line up with each other and there is a reasonable space between the subsystems. The result should look something like this:
Continue in this way and add all the subsystems in the block diagram. At the end of this the result should be something like:
Next, tidy up the circuit diagram by:
Then connect up the power supply rails, and the signals between the subsystems. The result should be similar to: The circuit could be further improved e.g. by moving components to straighten the connections. Because PCB Wizard does not have simulation facilities (these are available in Livewire and Circuit Wizard from the same company as PCB Wizard) it is not possible to check the design on screen. It is important to check the design before making a PCB, so use circuit simulation software, or a system kit, or build the circuit on prototyping board, before going to the next stage. When you are sure the circuit works as planned, the circuit diagram can be converted directly to a PCB using PCB Wizard (Tools > Convert > Design to Printed Circuit Board …). The result in this case will be something like:
It is prudent to check the PCB against the original circuit design before spending a lot of time making the PCB. Print out the PCB. Open the circuit diagram file and display the pin numbers (View > Display > Pin Numbers). Print out the circuit diagram. Check that each track on the PCB corresponds to a connection on the circuit diagram (a good way to do this is to mark each track and connection with a highlighter). The connection to the bulb is via the 2-pin terminal block. The PCB can be tidied up e.g. by deleting the unused pads and connecting any unused input pins on CMOS ICs to either 0V or +Vs to prevent damage by static electricity. The software used to produce the files for these notes was PCB Wizard version 3.50.
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