I am using Wemos D1 mini and trying to use ULN2083A Darlington Arrays to drive SRD-05VDC-SL-C relay. The relay does work properly when the circuit is connected as attached schematic.
The Darlington array (ULN2803A) would decrease the load voltage by about 1 volt across the internal transistor. If I have a 5V supply connect to the array and wish to use it to drive a 5v relay, the coil would end up receiving ~4 volt when it is activated. Is it acceptable? How would this affect on the relay?
I also tried the same thing to drive SRD-12VDC-SL-C relay with the 12v supply. The voltage would drop to about 11v as well. The relay does work but I have the same question, is it acceptable?
If the both scenarios are acceptable, which setup is preferable? Also, the circuit seems too simple to me, am I missing anything to improve it?