Selection of capacitors using relays in 8051

[Rockzinstruz]

Hi all,

In my circuit ,the capacitor selection obtained by relay circuits.By pressing the switch the capacitor has to be select using 8051 microcontroller.
Is this correct way to select the capacitor?Plz suggest the ideas regarding this design and is the another better solution? plz suggest here.



Thanks,
Rockzinstruz

 

[Rockzinstruz]

Here by,I attached the circuit for your reference.

View attachment 68028

 

[ChrisP58]

It would help us to understand what you are doing better if you used standard component symbols on your schematic.

But I think I can see what you're doing, and it should work. It's hard to say if it is the best way without knowing more about the rest of the circuit.

You do need to add clamp diodes across your relay coils to prevent the back emf from killing the transistors.

 

[Rockzinstruz]

Thanks for your reply Mr.ChrisP58 ,here attached the remaining circuit for your consideration.
View attachment 68047

View attachment 68048

 

[Jon Wilder]

The 8051 cannot drive relays directly. You'll need to use a transistor array...something like a ULN2803. The ULN2803 has the flyback diodes built onto the chip for driving inductive loads.

My favorite approach to this would be to use the external data bus to drive the relays. Here I have a schematic that shows how to do this even with an 8K memory chip on the bus. Driving output hardware via the external bus is awesome as it allows for easy expansion of an embedded system. You can drive quite a bit of hardware using this method -

**broken link removed**