Nano with 18v Doesn't Work - LED project

I though the Arduino Nano was able to handle up to 20v. My LED project works fine with 9v (from batteries) but when I connect two 9v together (18v) the on board LED's light up then slowly fade away and my LED strip connected to the system won't work either. Went back to the 12v system - no problem. I checked to make sure I didn't blow anything. So why no workie workie with 18v?

Hi,

It sounds to me like you are trying to destroy the Nano. May I suggest a hammer? Quicker and less likely to start a fire.

If you seriously want help understanding what’s going on, post a schematic diagram of how you have wired everything up and more details of these various led strips, power sources etc. A hand-drawn schematic will be OK as long as it is neat and readable.

At a guess, I would imagine you are trying to power both the nano and an led strip from 2 pp3 9V batteries. Those things are only suitable for very low current applications. I expect you are drawing far more current than they are designed to give and they, or the Nano’s poor abused regulator is overheating and so the voltage & current quickly fades.

Paul

What does your volt meter read, as the system stops working. 18 volts, or what?

Minus the Schematic - yes you are correct about the way it is setup. The nano has a negative and positive pin right next to each other. Im plugging in the battery directly into those. I have a common anode for my led rgb strip so I go right from the anode to the rgb strip with a 1k resistor in between.

Ya nothing got hot though…hmmm

Also, what’s the minimum value resistor I should use for a 12v rgb strip?

"Also, what's the minimum value resistor I should use for a 12v rgb strip?"

I am not clear on your question. Your arduino does not put out 12v. Are you using an external power supply to run the RGB strip?

UsernameZ: Minus the Schematic

Can't help you much without it.

UsernameZ: The nano has a negative and positive pin right next to each other.

You mean VIN and GND? Not the 5V pin, right? You would definitely destroy the Nano if you connected 9, 12, or 18V to that.

UsernameZ: I have a common anode for my led rgb strip so I go right from the anode to the rgb strip with a 1k resistor in between.

That made no sense. Explaining these things in English is hard, that's why schematics were invented.

UsernameZ: Ya nothing got hot though....hmmm

OK, so its just the battery's internal resistance. Draw too much current, the internal resistance causes the output voltage to drop.

UsernameZ: Also, what's the minimum value resistor I should use for a 12v rgb strip?

If you run a 12V strip off a 12V supply, no resistor needed. These strips have their own resistors built-in. If you run the strip off 18V (assuming a stable supply with enough current capability), then the resistor would depend on the current, which depends on the length, or rather the number of leds, on the strip. Also you should use 3 resistors on the 3 cathodes, not just one on the anode.

Usually, 12V rgb strips have the leds arranged in groups of 3. That's why you have to cut the strips between these groups, or some of the leds won't work. Each group of 3 leds will draw around 20mA for red, plus 20mA for green and another 20mA for blue.

A strip with 60 leds would have 20 groups of 3, so the current would be 20 * (20mA+20mA+20mA) = 1.2A. But that would be for white. Red, green or blue would only be one third of that, yellow, cyan & magenta would be two thirds. The point is, the current flowing in the common anode varies with the colour being displayed, so no one resistor value could be correct. But for the cathodes, the current would always be 20 * 20mA = 0.4A each. To drop 6V, your resistors need to be 6V / 0.4A = 15 ohms.

For a strip with only 6 leds, the resistors would need to be 6V / 0.04A = 150 ohms.

But all this is a bit pointless if you try to run an led strip of pp3 batteries, they just don't have what it takes. Maybe 2 pp9 batteries would work, but much heavier & bulkier!

^^^This guy.....now that's an answer! Thank you! Thanks to all! And to all a good night!

So you're saying 2 regular 9v batteries aren't enough power to run an rgb strip for very long?

What if I cut some of the strips off of the whole strip and then used a good size resistor? Would that give me a lot longer battery life?

Without a drawing/schematic, It is really hard to know what you have hooked to what. Such as, where is the led strip getting its power, what else is drawing power from the arduino, etc.

"I though the Arduino Nano was able to handle up to 20v" That's sorta like the ads that say "sign up to win up to $200,000 dollars" What are the ods?

Input Voltage (recommended) 7-12 V If I have a choice, I prefer to keep it close to 8 V.

No matter what voltage you supply the Vin pin with, (as long as it's 7v+ ), it still runs at 5v (it contains a regulator to output 5v for the chip). If you need to control higher voltages, you need to use transistors or mosfets.