16f877

Started by peter hadge March 6, 2004
hi all,
 
if i want to control 8 relays by the 16F877, could i connect these relayes directly to 8 output from the PIC without using any kind of buffers or any other components?
thanx




You shouldnt. Better use transistors to drive the relays.
 
Regards,
 
*Carlos*
-----Mensaje original-----
De: peter hadge [mailto:p...@yahoo.com]
Enviado el: Sado, 06 de Marzo de 2004 12:12 a.m.
Para: p...@yahoogroups.com
Asunto: [piclist] 16f877

hi all,
 
if i want to control 8 relays by the 16F877, could i connect these relayes directly to 8 output from the PIC without using any kind of buffers or any other components?
thanx




Depends on the relay drive requirements. Are they higher or lower than
the PIC is capable of driving. Most likely higher. --- peter hadge <> wrote:
> hi all,
>
> if i want to control 8 relays by the 16F877, could i connect these
> relayes directly to 8 output from the PIC without using any kind of
> buffers or any other components?
> thanx >
>
> ---------------------------------
>
=====
My software has no bugs. Only undocumented features.

__________________________________



Your 5V relay coils are likely to pull 80-100 mA. way too much for
the PIC. check this page out.
<http://ourworld.compuserve.com/homepages/Bill_Bowden/r_ctrl.htm> its
a good summary of how to drive relays. If you are using 5V relays,
you can use option B which doesn't require a resistor. I'm using
2n2222s to drive several 5V relays in my latest project. Dont forget
the diode for each coil as it keeps the smoke in.

By the way, you might also want to look at solid state relays. They
are bit more expensive but dont require the clamping diode or drive
transistor so its less space, a much cleaner layout and a far longer
life cycle. Inexpensive relays are often only spec'd for 100K
operations - cycle 100 times a day and it will last only 3 years.

--- In , peter hadge <pt2263@y...> wrote:
> hi all,
>
> if i want to control 8 relays by the 16F877, could i connect these
relayes directly to 8 output from the PIC without using any kind of
buffers or any other components?
> thanx >
>
> ---------------------------------
>