Some pretty basic questions

Hello everyone ,

Hoping someone can give me a little assistance .. My knowlegde of the component designing process is very limited.

My goal in this is pretty basic .. I want to light 2 L.E.D's but with the following specs.
1. Using Pots to control the LED brightness
2. Use a Photocell to turn on the lights automaticlly at dark.

I am using a wall wart with 7.5 incoming voltage ... going off of some basic information I am seeing that to light a red LEd with with a forward voltage of 2.0 I will need a resistance of 330ohms and to light A white LED with a forward voltage of 3.3 I need resistance of 220ohms.

The first few questions are how to use the Pots to to control this .. do I use it in series with a resistor , or will the pots alone work? and what should I look for in buying the pots?

I am attaching a simple graphic to how I "think" this circuit needs to be done .. it was a quick work in MS Paint so please be kind

thanks in advance to anyone who can offer some assistance.


-R

The photocell doesn't change its resistance low enough, and its response is backwards to what is needed. So it would be better driving a transistor that is an inverter and the transistor can turn the LEDs on and off.

You can try a 10k or 20k pot for each LED to control brightness but its action will be mostly at max rotation and it won't dim very much at min rotation. You must use your calculated resistors in series with the pots to stop the LEDs from burning out.