Nano Biscotte Help

[Jay-gon Jinn]

Resistors are used for limiting current, not necessarily dropping voltage. A voltage regulator is required for that.

[bruzer79]

Can I get a match check? Im getting conflicting\confusing results.... 4x ni-mh = 4.8 v - running a blue Seoul P4 - 3.25 ( can run up to 4) foward voltage - 1000ma.

For the LED; the resistor finder on the main page says I need 1.5 ohm 5 watt resistor, while http://led.linear1.org/1led.wiz says 1.8 ohm, 1.8 amp...

I also dont understand how the difference between a 2amp power source and a 1amp LED effects the equation.

[Forgetful Jedi Knight]

Can I get a match check? Im getting conflicting\confusing results.... 4x ni-mh = 4.8 v - running a blue Seoul P4 - 3.25 ( can run up to 4) foward voltage - 1000ma.

For the LED; the resistor finder on the main page says I need 1.5 ohm 5 watt resistor, while http://led.linear1.org/1led.wiz says 1.8 ohm, 1.8 amp...

I also dont understand how the difference between a 2amp power source and a 1amp LED effects the equation.

Ideally for what you have, you would need a 1.5 Ohm, 2W resistor.

The current (amperage) affects the second parts of the Ohm's law calculation that determines which wattage the resistor needs to be.
The calculator said you needed 1.8 Ohm, 1.8 W but since 1.8W resistors are not commonly made (or available) you would round up tot he next size (2W).

In my calculation, since I do the math and don't rely on a resistor calculator) I used the Vf value of 3.3V for a blue LED, and then your battery 4.8V and 1000 mAh (or 1A) for the current). The calculation formulas are in the NB manual.

[spits79]

Hello,

I'm completely new to this and have no idea about electronics, I noticed in the bruzer post he said he has a Blue Seoul P4 which he's running at 3.25v however the shop site list this led as max 4.0v. I don't understand how you can set a LED to run at a specific lower voltage and what would be the downside with doing that?

I ask as I was thinking of getting the NB to run a Green Seoul P4 (one of the led+headsink modules) but I was thinking of putting in a single single Li-Ion 18650 however if the calculations in the manual are correct obviously this wouldn't work since the led is 4.1v (max) and the cell is 3.7v.

Btw I was so green at this I had no idea where bruzer79 had pulled the 4.8v figure from since the store doesn't list the voltage of the ni-mh batteries. It wasn't until I was looking series and parallel wiring, quick lookup of AA batteries on wiki and it suddenly triggered

[Forgetful Jedi Knight]

Hello,

I'm completely new to this and have no idea about electronics, I noticed in the bruzer post he said he has a Blue Seoul P4 which he's running at 3.25v however the shop site list this led as max 4.0v. I don't understand how you can set a LED to run at a specific lower voltage and what would be the downside with doing that?

I ask as I was thinking of getting the NB to run a Green Seoul P4 (one of the led+headsink modules) but I was thinking of putting in a single single Li-Ion 18650 however if the calculations in the manual are correct obviously this wouldn't work since the led is 4.1v (max) and the cell is 3.7v.

All LED's have voltages that run within a certain RANGE. We use the average value of a specific LED color as a basis, since it will still work (maybe not at peak performance, but it will still work). In your case, a green P4 average would be around 3.4 Vf which would be UNDER the 3.7 battery voltage. If you use a 1 ohm, 1 watt resistor, your green P4 should work just fine.

[spits79]

Cool that's good to know but just for my interest is there like a rule of thumb here for calculation like this. For example following on the same idea if I wanted say an illuminated switch, the NB can give out 3.3v which is the max for the switches (3.3v 20mA) which again according to the calc in the documentation is (3.3-3.3)/0.02 technically is 0. Now I assume the same sort of situation applies where the average draw would be lower than the max but I don't know what this is.

[Forgetful Jedi Knight]

Cool that's good to know but just for my interest is there like a rule of thumb here for calculation like this. For example following on the same idea if I wanted say an illuminated switch, the NB can give out 3.3v which is the max for the switches (3.3v 20mA) which again according to the calc in the documentation is (3.3-3.3)/0.02 technically is 0. Now I assume the same sort of situation applies where the average draw would be lower than the max but I don't know what this is.

Simply put... it depends. It depends on the color of the illuminated switch. If it's blue or green, then you're basically safe, though a tiny resistor (1 ohm 1/4 W) is generally recommended for a a switch like that. If it's red or yellow, then you'll need a "bigger" resistor.

The 3.3V pad was designed with illuminated switches in mind, the switch LED's take 20 mAh, and the pad dishes out 20 mAh.

[mistersamsa]

Howdy all... way new to this. Running my Nano to the LED using a 1000ma buck puck. As soon as i plug in the batteries (running the 4 X AAA w/ the built in speaker) the LED comes on (solid, without the flicker). Once I hit the button (momentary) the sound and flicker comes on... what am I doing wrong?

So confused

[spits79]

Actually this brings up another point do you actually need a buckpuck with the NB, I've read some posts they say yes and other that say no. I would have thought you would, since I don't think there is no current regulation withe the NB? But I digress, following on with my questions around resistance calculations...

So with say with a green led switch the output of the NB is exactly the max of the switch diode so what is the purpose of the tiny resistance in this case?

With say a red led switch if you, wanted it as bright as possible, then the maths say it would require a resister greater than 80ohm 0.035W. So a quick look on the store shows a 82ohm 1/4W resister which would fit the bill (Is the important thing to get the amp down, but the wattage just needs to be close, is that right?)

[Forgetful Jedi Knight]

Actually this brings up another point do you actually need a buckpuck with the NB, I've read some posts they say yes and other that say no. I would have thought you would, since I don't think there is no current regulation withe the NB? But I digress, following on with my questions around resistance calculations...

So with say with a green led switch the output of the NB is exactly the max of the switch diode so what is the purpose of the tiny resistance in this case?

With say a red led switch if you, wanted it as bright as possible, then the maths say it would require a resister greater than 80ohm 0.035W. So a quick look on the store shows a 82ohm 1/4W resister which would fit the bill (Is the important thing to get the amp down, but the wattage just needs to be close, is that right?)

To answer your questions:

1. No a buck puck is NOT necessary.

2. Think of it as a tiny surge protector. It may come as a surprise to you, but newbies do have a tendency to make a mistake here and there and either fry or blow something up. I'm just trying to give your wallet a fair chance, since this is an expensive hobby.

3. Yes. Resistors only come in certain sizes, so you will likely have to round up (or down) to get the value closest to your calculations.