Running 5V NeoPixels from 3.3V Microcontroller
2020-Jul-29, Wednesday 11:59 pmAs I do more with electronics I get more complicated ideas, which necessitate learning more. At the moment I want to run 5V NeoPixels from a 3.3V microcontroller (i.e. Arduino Lilypad) which doesn't have a handy MOSFET pin (like the Adafruit Flora). I studied the NeoPixel best practices guide repeatedly. The new requirements boiled down to;
- 300 to 500 Ohm resistor on the Data In line of NeoPixel strip (which will be added to the NeoPixel end),
- capacitor (1000 µF, 6.3V or higher) across the battery terminals,
- logic shifter to up the 3.3V Data Out from the microcontroller to the 5V Data In for the NeoPixels.
Okay, great. Now where am I going to get the 5Vs from? 4AA rechargeable batteries would give me 4 x 1.2V = 4.8Vs, great. But, what if I accidentally grab alkaline batteries by mistake? That would result in 4 x 1.5V = 6Vs. Which is enough to damage the NeoPixels. To protect against thoughtlessness I would need a 5V voltage regulator. But, hang on, why don't I also add a 3.3V voltage regulator and remove the need to power the microcontroller with a separate power source? Just have to make sure everything has a common Ground.
Great, okay, so that's two voltage regulators. And the recommended bypass capacitors; 1µF on input and 0.1µF on output. This is a lot. Let's sketch it out. A few times by hand, then in Fritzing.
( Process )
Then it's time to commit it to solder. It all fits on a half-size breadboard, and you can use any, but the ElectroCookie board has a continuous ground line if you bridge the break, which saves me work. Also, bonus cuteness.
( Testing )
- 300 to 500 Ohm resistor on the Data In line of NeoPixel strip (which will be added to the NeoPixel end),
- capacitor (1000 µF, 6.3V or higher) across the battery terminals,
- logic shifter to up the 3.3V Data Out from the microcontroller to the 5V Data In for the NeoPixels.
Okay, great. Now where am I going to get the 5Vs from? 4AA rechargeable batteries would give me 4 x 1.2V = 4.8Vs, great. But, what if I accidentally grab alkaline batteries by mistake? That would result in 4 x 1.5V = 6Vs. Which is enough to damage the NeoPixels. To protect against thoughtlessness I would need a 5V voltage regulator. But, hang on, why don't I also add a 3.3V voltage regulator and remove the need to power the microcontroller with a separate power source? Just have to make sure everything has a common Ground.
Great, okay, so that's two voltage regulators. And the recommended bypass capacitors; 1µF on input and 0.1µF on output. This is a lot. Let's sketch it out. A few times by hand, then in Fritzing.
( Process )
Then it's time to commit it to solder. It all fits on a half-size breadboard, and you can use any, but the ElectroCookie board has a continuous ground line if you bridge the break, which saves me work. Also, bonus cuteness.
Finished circuit soldered
Photo by ![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
chebe
( Testing )
