I will be switching 24V/5W Solenoids,
The client has provided a separate 24V SMPS for supply to solenoids

I hope 7805 will work in this satisfactorily

I was trying to switch the relay from the uC today but it didn't work.

I tried connecting only ULN2003AN to the relay bed it work perfectly when I give VCC to 1B the relay connected 1c or pin 16 switches on

I have put a diode across the relay bed too ( not shown in ckt )
I checked using logic probe the following is the way I traced it
***
*After reset all pins are high
the relay does not switch on like before after reset

*when the button on pin 1.0 is pressed i.e. p1.0 grounded

*O/P of p3.1 goes low

*I/P of 74HC04 is low

*O/P through pin2 is high which is connected 1B of ULN

I am supplying ULN from a different 5V regulated supply.


************
My program *
************
What it does is basically check if the p1.0 has gone low if so it switches on p3.1 for 1 sec and turns it off

pin 3.1 is connected to 74HC04 and pin 2 of 74HC04 is connected to ULN2003AN (1b) as shown in diagram


$Mod51

Org 0000h
Sjmp main
Var1 equ r0
Var2 equ r1
Var3 equ r2
Dispbool equ 20h
;*************************************************

Delay:
mov var3,#8
mov var2,#8
mov var1,#236
Tt1:
djnz var1,tt1
djnz var2,tt1
djnz var3,tt1
ret

Main:
mov p1,#0ffh

Check1:
jnb p1.0,selrel
sjmp check1
Selrel:
clr p3.1
call delay
setb p3.1
sjmp check1
End


Thank you

Deepak