Hello! I'm working on a project where I want a arduino Uno (run by a battery pack) to make my LEDs light slowly "pulse".
The LEDs I'm going to use are about 50 warm white diodes on a string with a 3x AA battery pack from a store, all pre-connected and ready to use.
The problem is that I don't know how many volts and ampere the LEDS require. The paper note on the cord says nothing about it, and I've thrown away the packageing (bought it months ago when I didn't know I would be using it for this project)
How do I find a fitting volt and ampere level to run my Arduino and the lights for about 4-5 days? (It won't be on all the time, but just as safe measure) And could anyone help me work out a code to make the LEDS pulse?
Three 1.5V batteries is 4.5V so 5V should be fine. In fact, the LED strip is probably intended for 5V.
You can measure the current if you have a multimeter or you can estimate 10-20 mA per "typical" LED. A 1-amp power supply will probably work (or a little more for some safety margin).
The Arduino can only directly drive 1 or 2 LEDs so you'll need a [u]driver circuit[/u]. The MOSFET should be rated for 1 Amp or more. (You can leave-out the diode since you have a non-inductive load.)
How do I find a fitting volt and ampere level to run my Arduino and the lights for about 4-5 days?
From batteries? Alkaline AA batteries are rated for about 1 Amp-hour, so you'll only get about an hour if the LEDs were on full-time. You'd need a BIG battery! If they are pulsing you'll proportionally longer battery life depending on the on/off duty cycle.
You can get "extra" battery life with a higher-voltage battery and a switching (AKA "switchmode") voltage regulator. Switching regulators are nearly 100% efficient which means if you step down from 12V to 5V, you can get 1A at 5V while only pulling about 1/2 amp from the battery. Plus, you can drain the battery down beyond it's normal life to almost 5V which means you're getting more than the rated Amp-hours.
And could anyone help me work out a code to make the LEDS pulse?
A UNO is always a bad choice for battery-operated projects because it has the USB interface chip powered while ever it is connected, drawing power even if you put the main processor to sleep. And it is a clumsy format.
You should start with a Pro Mini with the pilot LED disabled and arguably the on-board regulator (which is pretty useless anyway) removed.