0
\$\begingroup\$

I'am working on a digital clock project with a PIC16F877. I'm designing the PCB with Proteus. The PCB contains mostly SMD components and I don't have any experience with that so I have some questions:

  1. Do SMD components work the same as through-hole components? Should I use the same type of copper plates and everything?
  2. For the PIC microcontroller, do I need to add a crystal to the circuit or does it have an internal crystal?
  3. Do SMD components have any space between them and the plate for the traces to go in between (like through-hole ones)?
  4. Where do I connect the 5 V input on the PIC? I am using a 12V adaptor as power source and I'm decreasing the voltage with 7805.

enter image description here

enter image description here

\$\endgroup\$
4
  • 1
    \$\begingroup\$ I'd say you have three separate questions here: one (two parts) about SMD components, one about the built-in oscillator and one about the 5V pin. Probably the second and third ones can be answered by reading the datasheet for the chip. \$\endgroup\$
    – user20574
    Commented Mar 23, 2023 at 9:32
  • 1
    \$\begingroup\$ 5 V adapter feeding a 7805 won’t give you 5 V output. Have you simulated your circuit? \$\endgroup\$
    – winny
    Commented Mar 23, 2023 at 9:33
  • 1
    \$\begingroup\$ The PIC16F877 has an internal oscillator but don't count on it being accurate enough for a clock. You need to configure it for an external crystal. \$\endgroup\$
    – Bart
    Commented Mar 23, 2023 at 9:36
  • \$\begingroup\$ May I ask if you actually mean "clock" (for the wall or table) not "watch" (for the wrist or pocket)? The power is quite a different matter! If it's for a table, consider using a USB supply directly for the 5V. \$\endgroup\$
    – jonathanjo
    Commented Mar 23, 2023 at 12:48

1 Answer 1

Reset to default
3
\$\begingroup\$

1- Do SMD components work the same as through-hole components? Should I use the same type of copper plates and everything?

SMD components work same as TH components, but, there is some difference. We use SMD components to reduce the area of them. Also, power of an SMD resistor, breakdown voltage of an SMD capacitor etc. can be changeable, you must reach them from datasheets or something else. Some THT components can be hard to find in SMD type. For example, high capacitance electrolytic capacitors.

2- For the PIC microcontroller, do I need to add a crystal to the circuit or does it have an internal crystal?

Some of the microcontrollers may have an internal oscillator, but an oscillator can be connected externally. The datasheet of the microcontroller used should be examined. When using a microcontroller with an internal oscillator with an external oscillator, programming changes may be necessary.

3- Do SMD components have any space between them and the plate for the traces to go in between (like through-hole ones)?

Pads are used in SMDs, while pads with vias are used in TH so that soldering can be done on the PCB.

4- Where do I connect the 5 V input on the PIC? I am using a 12V adaptor as power source and I'm decreasing the voltage with 7805.

After reducing the voltage to 5V with your regulator, you should connect the output of regulator to the microcontroller's VCC pin.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.