So...very new and very novice (ie inexperienced at all of this).
I'm more a wood worker by nature but would like to incorporate some backlighting in some table sized wood/epoxy lamps.
I'm using RGB LED 5050 strips (60 LED's/meter) that are 12V. I'll use 12 individual LED's (4 sections of 3) for each project. I'm assuming that a PWM Fading type arduino sketch will use about 0.12 amps of current for this project...1.2 amps/60 LED's in a meter; 12 LED's would use 0.24 amps if on full white light so about 1/2 of that for a fading set of LED's.
I tried running the 12V into the nano through the VIN pin and I think I burned the board out. The fading program seemed to work for a while but the board got very hot and after a short while the led string would light up but not fade or work as desired. When I tried reloading the sketch into the nano Arduino IDE would not recognize the nano nor the port which is what leads me to think I damage the nano. I was able to load the sketch on a new nano with no issue. Here's what I was following...I tried to upload the schematic I used to do this but I can only upload 1 image.
All this is to ask if I can wire the 12V to the RGB LED Strip and branch off of the 12V hot wire with a resistor to drop 7V and run that into the 5V pin of the nano? I tried mocking it up on EveryCircuit and I think it works???
I looked on line and saw a lot about voltage dividers...If I'm understanding the concept, I'm kind of getting the same results but instead of a second resistor to drain off the excess voltage, I'm drawing it off through the 12V LED's???
I hope this makes sense; I tried working this our rather than just asking how to make it work... But just when I think I'm making sense of circuits I fry something and have to start over. Like I said I'm better with wood
Thanks in advance for any advise and suggestion.
Sam
You shouldn't power the LED strip through the Arduino board. The LED strip (and the MOSFETs) should have its own separate connections to 12V and ground. so the current doesn't flow through the board. But I'd be surprised if that fried your Arduino.
12V should be OK powering the Arduino. It can get "iffy" if you are powering other things through its built-in 5V voltage regulator but the Arduino by itself should be OK.
Voltage dividers are not for power supplies. They are for low-power "signals" or "reference voltages". If you want to drop power supply voltage you need a voltage regulator. There is one built-into the Nano but an external voltage regulator can potentially handle more input-voltage and more current.
[quote]with a resistor to drop 7V and run that into the 5V pin of the nano? [/quote] Do not connect more than 5V to the 5V pin! 7-12V can go into Vin which then goes through a 5V voltage regulator.
Your picture shows an LED strip with a chip. If it's an addressable LED strip the driver circuitry is built-into the chips and you don't need MOSFETs.
Absolutely not, you will fry it. Resistors drop voltage according to Ohm's law, which means the voltage depends on the current, which will vary. Ideally use a buck converter as they are very efficient. Lots to be found on your favourite e commerce site.
No this is for the 5050 Non Addressable Strip. Don't know why that strip looks the way it does.
So I'm assuming that means 2 power cords and 2 plugs to find an outlet for. I was trying to avoid that as it just seems bulky for a table top lamp. Would a Buck's Converter allow 1 power cord?? (I'm planning on reading about these after I post)
Please explain a little more what you mean by varying current...
Do you mean that the current variations are due to the fading in and out of the LED's being controlled by the nano sketch?
I found the following specs for this string of LED's: Working Current:0.35-1.2A / M...60 LED's/M....I'm using 12 LED's so my working current is 0.07-0.24A (70-240mA)
R=V/I Resistor Range of 171 to 50 Ohms. That seems to correspond to a power range of 0.9 -3 Watts using P=I^2 * V...So am I right in assuming the resistor will fry (even if I used a 1W resistor) and the nano will be next in line??? That seems like a lot of wattage for 4 series of 3 LED's??? I feel like I'm missing something here?
Thanks again for helping guide me through these currents.
Sam
That can happen when you have connected the Nano to USB, with the 12volt supply and LED strip connected to V-in, and without the 12volt power supply actually running.
USB power will then go backwards through the 5volt reglator to V-in, trying to power the LED strip.
Back-powering the 5volt regulator will destroy it, and the next time you power up the 12volt supply you will fry the Nano.
The Nano V3 design should have had a diode inline with V-in (like the Uno has on the DC socket).
You could add that diode externally, between 12volt and V-in, cathode/ring towards the Nano.
Leo..
To be clear I am talking about the 100Ω resistor powering the Nano in your schematic in post #1
From your comment I assume you understand Ohm's law and I am going to assume you understand Kirchhoff's circuit laws too.
You need 5V at the 5V pin of the Nano, which means that for a 12V supply you need to drop 12 - 5 = 7V. I believe you understand this already. 7V across a 100Ω resistor gives a current of 7/100 = 70mA. Your circuit therefore assumes that the Nano draws exactly 70mA and this never varies. You cannot assume the Nano draws 70mA and you cannnot assume it never varies, neither of those two statements will be true. As soon as the current varies the voltage across the 100Ω resistor will vary, varying the voltage supplied to the Nano. Sooner or later the voltage on the 5V pin will be too high and the magic smoke will escape from the Nano.
One of the things that will definitely cause the current to vary is turning external thing, such as LEDs, on and off.
