I have an arduino with a RTC clock that can turn an LED on and off. I now to want to use this control the lighting up of a small LED snowman.
I am using this as a guide: using a transistor as a switch
So my idea was to have the Ardunio powered by a 9v battery than came in project pack, and the use the the 5V output pin to power the LED snowman circuit and use the 3V ouput pin to control the clock with transistor to 'switch' on the output circuit? Timer would be 6hrs on 18hrsoff.
Am I over complicating it ? What I really don't understand is to calculate how long the battery will last. The snowman seems to draw .2Amp according to my bench power supply set to 4V DC, I just hooked up the leads with a resistor till it lit as bright as i wanted and read off the amp reading?.) No idea how to go about this really.
use the 3V ouput pin to control
How? The 3.3V output can't be digitally controlled.
The battery will probably last about 15 minutes, according to the readings you made.
So the 3v pin was just going to be used to power the circuit with the transistor, and the 5v to power the circuit with the snowman, and then the clock to ‘switch’ the transistor.
So the 3v pin was just going to be used to power the circuit with the transistor,
Why? Have you made any drawings to post? It would be immensely helpful. Similar to the one that is with the tutorial you posted a link to...
The common emitter circuit in the tutorial isn't "powered" from any voltage source. The load is connected to that, the base drive comes from some digital output.
Please do not post off site links. Post images by attaching them.
You haven't answered the first question in reply #3. Or responded to the problem stated in reply #1. If you know of a way to turn the 3.3V pin on and off in software, I would really like to hear about it. You didn't include any current limiting resistor to the transistor base. Also, what is an "Arduino/clock"? That kind of vague description won't be enough to design a thing like this.
Please draw a complete schematic (one that shows all the components) and attach it to your post. It is especially important because you have mixed supply voltages (apparently).
You will prob. need a current limiting resistor for the snow man.
You will need a current limiting resistor on the transistor base, use 1k or so.
Instead of the 3.3 volts you can either use a digital i/o pin and turn it off or on.
Hooked up to 3.3 volts that is always on. You could use the 3.3 volts but then
you would have to connect the emitter of the transistor to a digital i/0 and switch
that pin to low to turn the snow man on and switch the pin high to turn the snow man off.