sexta-feira, 1 de julho de 2011

Choosing the components


Today our discussion is about the connections between the microcontroller and peripherals.
As important as certain components, or their links, are also the values used, follow  two examples:
A capacitor used to debounce won't work for a very low value, and will affect the speed of the button if it is too high.
Already a poorly chosen can give a resistor voltage drop very low and fry the next component, a drop too high could cause the component bound hadn't enough voltage to "connect".
The HT1380 is responsible for external clock, and must be used along with a Crystal, its clock 500kHz, then we will use is a crystal of 33kHz.
The LM is a 7805 voltage regulator, will be used to download the 9V voltage to 5V stack that will be used in the circuit. To use it you should take special care not to invert the pins.
The LM 35 is a temperature meter that can measure temperatures from -65C to 150C, I do not think anyone go take our watch to the South Pole nor inside the oven, then this component will be enough for our needs. This component also requires correct placement of the pins.
The following is a table with the values of the components your codes adopted in schematic and their functions. 


Componente
Valor
Função
U1
MSP430F2013
Microcontrolador
HT
1380
Clock externo
LM 7805
5V
Regulador de tensão
LM 35
5V
Sensor de temperatura
R1
47KΩ
Resistor
R (2-10)
10KΩ
Resistor
C (1-5)
100nF
Capacitor
C (6,7)
5pF
Capacitor
Pot1
10KΩ
Potenciômetro
Osc
32KHz
Cristal 
Bat
9V
Bateria (Vcc)
J1
-
Conector
S (1-4)
-
Botão  

You can find the datasheet of the components in our site https://sites.google.com/site/embarcadosunifei/home/arquivos-do-blog:

Below there’s a picture to clarify the correct positioning of the LMs:




The following image is Schematic of our future clock:
The sign "*" in capacitors and resistors mean that they are not absolutely required, the resistors are pull-ups, and the capacitors are for debounce. 


Nenhum comentário:

Postar um comentário