OK, I have a Nano project involving: 12v LED lights; a sound card (DFPlayer pro) powered by the 5V pin on the Nano; 6v electromagnets and a motor. The electromagnets and motor are switched using MOSFET power controllers.
So ... a 12v 4A constant voltage power supply runs the LED tape. Then I am using a Buck converter to reduce the voltage to 7v to power the magnets and the motor via the MOSFETs.
Everything goes fine when the Nano and the sound chip are powered by a USB cable running from my Mac. But when I unplug USB and power the Nano with 7v through the VIN and GND pins, the sound card doesn't switch on. My sketch has code to initialise the sound card and send it commands -- this code just fails.
HOWEVER, when I tweak the Buck converter to supply 9v, everything works. OK, I can live with this arangement, but the rated voltage for the motor and magnets is actually 6v. They work fine at 9v but I worry that the motor will not like the over-voltage, and the magnets may get hot. I don't really want to add another Buck converter to step the voltage down to 6v. I guess I could put heat sinks on the magnets.
BTW, why do I need a 4A power supply, when the whole thing draws only a little more than 1A? Because when I used a 2A supply, the LEDs dimmed when the magnets were powered up.
FYI Here is the finished project. It's a stained-glass panel.
https://youtu.be/_-ShUhxq2mo
Thanks for eading to the end!
I like about 7.5 to 8.5 volts on the Vin. I do not power the external hardware with the Arduino as it tends to fry them. Buck converters are inexpensive use one for each of the voltages and all should work well. It sounds like you are overloading the onboard regulator. Here is some help:
Gil's Crispy Critter Rules, they apply to processor hardware:
Rule #1. A Power Supply the Arduino is NOT!
Rule #2. Never Connect Anything Inductive to an Arduino!
Rule #3 Don't connecting or disconnecting wires with power on.
Rule #4 Do not apply power to any pin unless you know what you are doing.
LaryD's Corollary's
Coro #1 when first starting out, add a 220R resistor in series with both Input and Output pins.
Coro #2 buy a DMM (Digital Multi-meter) to measure voltages, currents and resistance. Violating these rules tends to make crispy critters out of Arduinos.
Hint: It is best to keep the wires under 25cm/10" for good performance.
Many thanks for your prompt and useful reply, and thank you for Gil's Crispy Critter Rules
I get this. I understand that the Arduino is not a power supply. But the sound card draws only 50 mA max, so it should be fine to run it from the Nano's 5V pin, and all circuit diagrams for this card show it wired that way.
I have wired all the power-hungry components through MOSFETs, so they aren't making any demands on the Nano.
So my basic question remains unanswered: why doesn't the sound card work when I power the Nano at 7V, but it does work when I supply 9V?
I can only take a SWAG as I cannot follow your schematic but It appears the 7V is collapsing or the regulator needs a bit more voltage again assuming Vin
Thanks, that’s a help.
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