#ARDUINO NANO PINOUT FUNMOVE HOW TO#
#ARDUINO NANO PINOUT FUNMOVE DRIVER#
#ARDUINO NANO PINOUT FUNMOVE PC#

However, those had enough capacitance to even out the voltage creating a constant ~10V, preventing any switching. I did look at using a 470nF and 1uF electrolytic capacitor. In my case, I just connected a 390nF Ceramic capacitor for C2 and all was good.

Normally you could do a bunch of math to figure out an ideal resistor-capacitor combination.

#ARDUINO NANO PINOUT FUNMOVE PC#

The current limiting resistor (R1) and capacitor (C2) form an RC network, which reduces much of the noise.įigure 6: Final Arduino PWM PC Fan Circuit Picking the PWM Filter Capacitor Connecting a capacitor from the NPN’s collector to ground slows down the edge into the base of the PNP. A simple solution is to slow down the edge to the OFF to ON transition. All of those little spikes are EMI noise. That’s what is making its way onto the hall-effect sensor. There is a lot of what we call “high-frequency content” in that edge. The edge rate from the Arduino I/O pin, and the NPN connected to it, transitions from LOW to HIGH incredibly fast. Instead, it is how fast the PWM signal switches from OFF to ON. So what’s going on here? Where are those spikes coming from? The spikes are EMI from high frequencies in the PWM signal.īut wait, the PWM signal from the Arduino is only about 600 Hz. It falsely triggered the interrupt, messing up an RPM measurement. Once this was all setup, I connected my scope and saw the following:Īll of the noise spikes shown are finding their way into the I/O pin. Filter Capacitors Help when you PWM a 3-Pin PC fan with an Arduino This relationship keeps the PNP, and the motor, OFF.Ģ. Since current can’t flow through the NPN, the cathode of the junction diode is effectively floating, meaning it will show the 12V connected to its anode. So that means if there is 12 volts on the Emitter, that is the anode of the junction diode. So that leaves the PNP’s base resistor floating. The NPN turns into an open because it’s Base-Emitter junction is off. Now, when the I/O pin goes LOW, something more interesting happens.

The transistor turns ON and the motor spins. This path allows 0.7 volts to drop across the PNP’s Emitter to Base junction. It turns on the NPN, which connected the PNP’s base resistor to ground.

#ARDUINO NANO PINOUT FUNMOVE DRIVER#

In Figure 3, I’m showing what happens with the NPN-PNP driver when the Arduino drives 5 volts. When the NPN drops to ground, then V BE becomes active, and the transistor turns on. This mode will prevent 0.7 volts from dropping across the Base-Emitter diode keeping the transistor OFF. The NPN can pull the PNP’s base, with its current limiting resistor, to 12 volts. This driver would allow the PNP’s base to see a wide voltage range. If we add a NPN transistor before the PNP, it can be used to switch the high-voltage supply on and off. It seems kind of silly doesn’t it? Well, doing things right isn’t always easy.

#ARDUINO NANO PINOUT FUNMOVE HOW TO#

To solve the problem of how to use a PNP transistor with an Arduino, you need to add an NPN driver. If you looked at the collector (shown as pin 2 in this diagram) on an oscilloscope, you’d see it stay a steady DC voltage. And you create an awkward voltage divider between the I/O pin and the base of the transistor. So the problem is that when the I/O pin is HIGH or LOW, there isn’t enough voltage to turn off the transistor. This circuit does present a problem when using 5 volts on the base and 12 V on the emitter.įigure 2: Oops. Instead, we can use a PNP transistor for the high-side switch. You were probably expecting it to be 11.3 volts, weren’t you? Well, that’s not how a NPN BJT works. Which means if there is 5 volts at the base, you only get 4.3 volts at the collector. When configured as a high-side switch the voltage from across V BE remains 0.7 volts. This circuit type switches the high voltage on and off, instead of ground. The proper way to power a fan is with a high-side switch. However, the lack of ground path means the switching can create electromagnetic interference (EMI). Regarding the fan’s operation, it will turn on and off as you expect.

This method doesn’t provide a return path when the FAN is turned off. However, the problem with this approach is that you are switching the ground (GND) path. Most tutorials show an NPN transistor driving a motor as a low-side switch. This post addresses all three issues regarding how to PWM a 3-pin PC fan with an Arduino.

Create a non-blocking RPM measurement (with millis()).

Working through the question, I found three issues to tackle: The noise made it impossible to measure the fan’s rotation. The problem was that the hall effect sensor, or TACH signal, was incredibly noisy. Controlling the fan was seemingly straightforward. A question came up on IRC regarding how to PWM a 3-pin PC fan with an Arduino using analogWrite().

Arduino nano pinout funmove