Saturday, June 30, 2012

Time Switch_2: Selecting equipment.

In any product design this step is of utmost importance. This is due to several factors. First one is that the performance of the system you design will be depending on the equipment/components you use to create it. Next is that you should purchase the equipment keeping at least one from each critical components redundant. So if you have mistakenly broken one critical component you can use the spare. Another reason is that some equipment needed to be purchased directly from the manufacture so it will take some time to reach you due to shipping, so you will be able to order components keeping a time cushion for safety and you will be able to meet the deadlines.
What are the most critical equipments in the TS?
First is the processor. Here I used a PIC16F628A. This is one of the very basic micro-controllers that you can purchase for around 1$. Due to the simplicity of the project, we don’t need to buy any sophisticated micro-controller. This is just a choice. This can be done by using any other processors (Atmel AVR, etc.).
The tasks that I want to accomplish using this micro-controller are quite simple. I want to of course drive around five switches (the number of switches will be decided later, for now we’ll plan for five). I want a LCD display to control these switches. I want a keyboard/keypad to insert commands.
We’ll forget about power supply for now and just think about the main board. I need relays to drive AC switches. I need transistors to drive the relays since they need high current (output current of a PIC is limited, so we need a current driver to drive the relays). Those are the most critical parts. Some capacitors, resistors and diodes will also be needed.
All the equipment I stated above are available everywhere.
Relays should be able to be driven by a mere 5V. That should be kept in mind. And the LM016L LCD display will be used here. I chose it because I have it with me :) and also it is available in the market for around 5$.
With those equipments in mind we’ll proceed to the next step.
:)


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