That circuit seems way over-complicated just to switch an led. Why not just use a transistor? If you can switch the ground connection to the 12V led, you just need an ordinary npn transistor and a base series resistor. If you can only switch the 12V connection to the led, you will need a pnp transistor and an npn, plus some resistors.
However, nothing in the circuit you posted would prevent multiple lamps from being switched on. Perhaps you have a bug in your code. Please post that, but read the forum sticky post first to find out how to post code on this forum.
Appreciate your quick response,
The circuit diagram posted is actually a 12VDC x 4 relay card which is a small part of the larger project. The main project being Surface grinder automator, which has Push buttons, LCD display, Proxy sensors, MPG pendants, stepper motors drives etc. interfaced to the arduino. Now that being said, the code is too lengthy to post on the forum, however the essential codes i will post here.
Also, it is unlikely that there is a bug in the code, as the onboard LEDs for signals on relay card are switching according to the code which means that the code is perfect.
There can be a possibility of incorrect power wiring, hence i am attaching the power wiring and signal transmission diagram along with.
Code for LED Indicator lamps :
const int LED_RUN = 46;
const int LED_STOP = 47;
const int LED_READY = 48;
if (CYC_RUN == 1)
if (CYC_RUN == 0)
if (CYC_STOP == 1)
if (CYC_STOP == 0)
if (CYC_READY == 1)
if (CYC_READY == 0)
Rishi R. Soni