Updated -Using the Digital Ouput to provide a ground signal

Let's try this again - thanks for the advice

Objective: Take regular 12vdc Light bulbs (not LED) and make them blink.

My experience with electronics : great building the circuits - not enough knowledge to create one.

My experience with Arduinos : I built one kit for R2D2 for the lights - it was already programmed. I do have experience with programming ( VB, COBOL, and machine code for the HASS CNC Milling machine)

Current setup - I have 12 vdc connected to the light bulbs - ground signal turns them on and off. This was working until I had a problem with the I/O board that interfaces with robot to my laptop computer. This is all pretty old - created back in 1999.

So, the question is how do I get a ground output from the digital outputs of the Arduino. I ike this idea of using a transistor that is turned on by the output signal - which in turn provides a ground to that line.

Could someone show me the circuit and what parts I should be using. Thanks!!!

Do not connect 12 in some way to the Arduin pins. The Arduino will be broken.
The 12V will go via the light into the Arduino pin, destroying about everything.

The pins (as output) can supply 40mA, but 20mA is a safe value.
So if an output pin is 5V, it can supply 20mA.
And if an output pin is 0V, it can ground 20mA.

You need a transistor or mosfet or relay to control the lights.

Hi! Just getting started in this - don't know if I'm going up the wrong tree. I want to use a program to make 12 volt light blubs blink.

Perfectly possible with an Arduino.

The bulbs have 12 volts wired to them

I presume these are filament bulbs and not LEDs

  • can I get a ground to each bulb using the digital output port on the Arduino.

Not the way to do it. You'll have to use a transistor to switch each bulb on/off, as each output pin on an Arduino can only supply 40mA. Not enough for a filament bulb.

I have not purchased one yet - thought it would be a good idea to see if this is possible.

You'll not be able to blink filament lamps quickly, as they take time to reach full brightness when you turn them on and time to stop shining when you turn them off. Fast blinking will make them give a continuous dull light,

You might find it more expedient to follow SOP on the forum . It is customary to begin your first post by stating your OBJECTIVE.
Include :
LINKS to vendors of equipment that is having issues.
Point being , I am sure this is going somewhere but at the moment nobody knows because all we know is that sometime somewhere , for reasons we may never know, some 12 V lights are going to blink. If you just spill the beans we can design this circuit and you can get busy blinking lights.

Go ahead, buy one, play with it, write a sketch to flash one lamp with a MOSFET, add more lamps.
Have fun.