Simple lighting. 1 blue LED, 1 9vt Batt, switch
- Thread starter joeranger
- Start date
propmaster2000
Sr Member
Hey joeranger,
A 9v battery connected to any LED with no resistor will kill it....
You WILL need to limit the current through the LED by the use of a current limiting resistor in series with the battery and switch.
You can use a 1000 ohm (1K) resistor for adequate brightness (you can go as low as 470 ohm) at 1/8w to 1/4w.
It all depends on the type of Blue LED you have.
There are many different chemical make-up (doping) of LEDs.....
I hope this helps
.
A 9v battery connected to any LED with no resistor will kill it....
You WILL need to limit the current through the LED by the use of a current limiting resistor in series with the battery and switch.
You can use a 1000 ohm (1K) resistor for adequate brightness (you can go as low as 470 ohm) at 1/8w to 1/4w.
It all depends on the type of Blue LED you have.
There are many different chemical make-up (doping) of LEDs.....
I hope this helps
.
Last edited:
propmaster2000
Sr Member
To be safe, use 1 resistor for each LED you use.
You can get electronics on eBay, Mouser, Digikey, All Electronics (in Cali.)
You can get electronics on eBay, Mouser, Digikey, All Electronics (in Cali.)
AndyJ
Active Member
Unless you supply at or below the rated forward voltage of an LED, it will draw current at an exponential rate and fry itself out. You need either:
A) A resistor to limit the current, you can calculate the exact value here but really anywhere even kind of close will be fine. Most regular LEDs will draw about 20mA.
B) Multiple LEDs in series, enough that the supply voltage is dropped enough between all of them to be at or equal the forward voltage. This dumb, only technically works if all the LEDs are the same, and is a bad idea.
C) A regulator to reduce the voltage to the correct forward voltage. You can pick up cheapo switching regulators here, or linear regulators here. The switching regulators are smaller but deliver less current.
Learn all about LEDs at Adafruit:
https://learn.adafruit.com/all-about-leds/overview
A) A resistor to limit the current, you can calculate the exact value here but really anywhere even kind of close will be fine. Most regular LEDs will draw about 20mA.
B) Multiple LEDs in series, enough that the supply voltage is dropped enough between all of them to be at or equal the forward voltage. This dumb, only technically works if all the LEDs are the same, and is a bad idea.
C) A regulator to reduce the voltage to the correct forward voltage. You can pick up cheapo switching regulators here, or linear regulators here. The switching regulators are smaller but deliver less current.
Learn all about LEDs at Adafruit:
https://learn.adafruit.com/all-about-leds/overview
joeranger
Sr Member
Well $50 at Radio Shack and now I am an "expert". I had to buy an entire combo pack of resistors to get the three 39 ohm's I needed.
I am starting to get it. You just use a LED calc program which tells you exactly what to do.
4 AAA batteries, 3 5w blue LEDS, 3 39OHM resistors. A new solder gun....
I am starting to get it. You just use a LED calc program which tells you exactly what to do.
4 AAA batteries, 3 5w blue LEDS, 3 39OHM resistors. A new solder gun....
AndyJ
Active Member
Nice work! And more importantly, you now have this knowledge in your brain
If you plan on doing this more, you might consider picking up some 500ohm trim pots that act as variable resistors and can be set to any value between 0-500ohms. They're too wimpy for very high power LEDs, but are plenty good for little 5mm guys like that.
There are also a plethora of smaller power options available. Adafruit has a little board that holds a single AA and boosts it to 5V, and they also have a plethora of small LiPo batteries and combo charger/booster circuits.
