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I have a Arduino which I would like to use to control a 12v PWM fan for speed control.
I know about the 0-3.3v to 0-5v logic level shifter, is there a similar option for 0-5v to 0-12v? Or is there a circuit using a IC that I need to make?
Thanks in advance for your help.
I advice you to learn about basics of how to connect external components to MCU. Anwser to your question is simple transistor amplifier... So you can use bipolar transistor (NPN/PNP) or MOSFET... MOSFETs is better for switching like your case, switching via PWM.
If you switching inductive load with MOSFET like motors or coils, don't forget add antiparallel flyback diode. Otherwise your MOSFET will burn out.
If you need switching with higher frequency or load with more voltage or power I advice to use push-pull logic to drive mosfet gate.
Something like this:
As far as I can tell the Arduino does not have open collector outputs, so you can mimic one as follows. The following inverts the Arduino output signal, so some adjustment is needed there when generating the PWM signal.
Excuse the rather gross schematic. I can't find any scaling parameters.
The particular resistors values are not terribly important, mainly to limit current.
simulate this circuit – Schematic created using CircuitLab
Use MAX232
Advantages of MAX232:
It has low rise/fall times. A good PWM needs to be sharp. Since MAX232 is designed for serial port communications, i.e., TTL to RS232 and RS232 to TTL, it has to perform reliably. Reliability ensures low rise/fall times.
It operates at low currents. The OP suggested that the fan only needs a PWM to drive, i.e., it has its internal current amplifiers.
It is cheap. Engineering solutions require to be no more expensive than it has to be, and MAX232 is half the price of L298.
Shortcomings of MAX232:
Shortcomings of L298:
L298 is a current amplifier, not a voltage booster. Using it for a purpose other than its primary purpose is suboptimal.
L298 has a huge current output. It might exceed the threshold currents of the fan, and cause malfunction. It is very unwise to connect a 1A rated L298 to 0.5 mA rated signal pin.
L298 has a weird pin diagram. It has a ZIP package rather than the regular DIP to allow attachment of heatsinks, which increases the size of the circuit.
L298 has high rise/fall times. Its purpose is to generate large currents, not PWMs. Therefore, its rated rise/fall times are not only high, but also unreliable.
L298 requires four high current rated Schottky diodes. The cost of these diodes will be more than that of the L298 and they are very large, resulting in a much larger circuit area.
Do you really want to use an H-Bridge? Use L293D.
L293D is still a current amplifier but not an overkill like L298. Its current output is four times as low as L298 so chance of malfunction is reduced.
L293D has a DIP layout. Most hobby electronics application uses DIP sockets to mount the ICs later on and you can do it with L293D.
L293D has the flybacks diodes internally. So you neither need to buy nor place them on your circuit.
Do you want to design your own circuit? Use a gate/base recharge/discharge transistor.
Basically, all transistors have a gate/base capacitor which needs to be charged before the transistor switches to ON and discharged before it switches to OFF. Power amplifiers normally do not care about the rise/fall times, with a notable exception that comes to my mind is musical amplifiers.
What about a discharge resistor?
Replacing discharge transistor with a simple resistor works but it would increase your drain from the PWM source. It has a simplicity vs performance trade-off.
Commenting about relays
Relays usually have a higher switching time because their input module consists of a diode and output module consists of a transistor, i.e., you have add their reaction times together. This results in distortion in the PWM output. Furthermore, there is no need to use SSR in a low power operation, an opto-isolater would suffice.
Final comment about designing circuits
Circuits have many trade-offs. Cost, availability, complexity, size, performance are just to name a few. A good design needs to take everything into account. To rate my above suggestions:
So, I would rate L298 as the worst possible solution that actually works.
I am not sure about this but you might not even have to use diodes of the L298 since your output voltage will always be unidirectional (or positive.) Yes: flyback diodes are always needed for any inductive load, to prevent the voltage spike which would otherwise occur any moment you turn off the load and the electromagnetic storage energy in the inductor collapses and drives a voltage spike. When throttling a motor, this occurs every PWM cycle, and when using pure ON with 100% duty cycle (therefore, no PWM), this voltage spike will still occur...
Oct 13, 2020 at 16:50
You'd usually use a transistor to do that.
simulate this circuit – Schematic created using CircuitLab
SW1 is your microcontroller creating the PWM signal.
Unless the output power is to be used to drive something, it is a bad idea to use BJT. MOS is way more reliable with lower gate current and gate capacitance. This is exactly the opposite of the truth. BJT doesn't have a Gate, nor does it have Gate capacitance. It has a Base, and the Base capacitance is so insignificant it isn't even mentioned on a BJT datasheet. MOSFETs, however, have very large Gate capacitances on their datasheets. The tradeoff is power and current. BJTs drive up to ~5A max (ex: TIP120) for the same physical size MOSFET which could drive 60A (ex: IRLB8721).
Oct 13, 2020 at 17:07
MOSFETs are typically used low power logic circuits? True, in part I'm sure because they don't bleed current. They are voltage-controlled, not current-controlled, so they don't require continual current flow to stay on, unlike BJTs. Because MOSFETs allow faster switching. I'm not sure this is true. hence lower gate capacitance very false. and lower power very true, because they (MOSFETs) are voltage-controlled, not current-controlled (BJTs are current-controlled, and hence continually bleed power just to stay on).
Oct 13, 2020 at 20:52
Note: my entire answer below assumes you need to drive a 2-wire brushed DC motor (or similar load, such as an audio speaker) directly, with real power and real current. That is what my entire answer is based on. However, after I wrote my answer, the OP posted this in a comment under his question (emphasis added):
I didn't have the serial number of the fan until today, now I have that I have checked the spec, and a low powered option is suitable as it only requires a PWM signal to control the speed the rest is done with its on-board controller - no more than a 0.5mA signal is required.
So, although my answers below will still work to provide an output PWM at, lets say, 12V, from an input PWM at 5V, they are intended to drive a 2-wire brushed DC motor directly with real power and real current. The fact that they can also provide an output PWM signal at 12V is incidental, but just as applicable.
Also, it is important to note that all my answers below are expected to be usable up to a few dozen kHz max PWM frequency, unless otherwise stated on the product datasheets--Ex: many high-end Pololu brand motor drivers (H-bridges) I recommend below can be driven with up to 100kHz PWM frequency since they use such high-quality and fast MOSFET Gate driver circuits with both high-power active Gate drive HIGH and active, high-power Gate drive LOW in their H-bridges.
Jump straight down to the section titled "Here's some H-bridges you can buy", in the "Option 2" section below. Buy one of those and be done.
Reminder: on any H-bridge, when you drive a PWM to the input at 5V with a certain duty cycle and frequency, an equivalent or almost-equivalent PWM output at voltage level Vsupply will occur on the H-bridge output. This is the exact purpose of the half-H-bridge. And, this, in addition to allowing bi-directionality of power, current, and voltage, is the exact purpose of the full H-bridge. PWM output freq from the H-bridge will be exactly identical to the input PWM, and PWM duty cycle will be almost identical, with output PWM waveform distortion increasing as PWM frequency is increased.
I've upvoted @Sahasrar's answer. If you haven't taken a look at it, you should. It fits squarely into this "Option 1" category.
However, in his first image, when controlling pin D7, the MOSFET gate is actively driven both HIGH and LOW with a max (initial) current of I = V/R = 5V / 100 Ohms = 0.05A = 50mA, which is good, but kind of weak (a good MOSFET gate driver is more like 500~1000mA drive current). This is also exceeding the 40mA max current rating of the Arduino pin, so I recommend you choose a slightly bigger resistor. The resistor here is to limit current to not damage your Arduino pin when charging and discharging the Gate capacitance of the MOSFET, which capacitance is significant enough for MOSFETS (but NOT BJT transistors), that it is even listed as a parameter in a MOSFET transistor datasheet (but not in a BJT transistor datasheet). WithOUT this Gate resistor, each time you drive the Gate HIGH or LOW, you'd otherwise have the equivalent of a momentary instantaneous short through the Arduino pin, which could damage the pin.
Also, you have to be sure to use a Logic-Level N-Channel MOSFET which can be driven with a gate voltage as low as 3.3V~5V instead of requiring more like 10V~12V.
So, with @Sahasrar's first circuit, the max PWM frequency you can use is probably a few dozen kHz.
If you need to drive higher PWM frequencies, the solution is to use the push-pull logic circuit which @Sahasrar shows next instead. But, you have to fill in the blanks: choosing parts, doing calculations, having advanced knowledge.
In both cases, you must also be sure to use a flyback diode to snub inductance-induced voltage spikes!
So, the quick solution is to just buy a motor driver instead and be done!
You can use any H-bridge for a 1-channel (1 device) bi-directional drive, or for a 2-channel (2 separate devices) uni-directional drive.
Or, you can use a half H-bridge for a 1-channel uni-directional drive.
H-bridges are frequently called "brushed motor drivers". They handle all the fancy Electrical Engineering circuitry for you.
tone() librarytoneAC() library
toneAC library, a large speaker, and a custom driver or H bridge:
TMRpcm libraryWhen searching for these things, recommended search terms include "DC motor driver" or "h bridge". Even if you plan to drive an LED or speaker with it, these are still the correct search terms and parts. Just make sure what you buy accepts PWM input as the control signal is all, and that this PWM input means true PWM, NOT a servo "PWM" signal, which is very different.
Just buy one of these and be done:
Important: since this option does NOT give you the low-level control over the PWM output directly, these controllers can NOT drive speakers for audio, whereas Option 1 and Option 2 drivers above can!
I'd be remissed if I didn't include this answer as well, since this is one of my specialties. This is the easiest by far! Its only downside is it gives you less fine-tuned control than controlling the low-level PWM output to the motors directly, as you can do with the motor drivers above, versus the motor controllers below. Another advantage of the hobbyist RC brushed ESCs below over the Pololu-type robotics motor drivers above is power and current: the above motor drivers from Pololu peak out at 25A continuous, for instance, whereas some RC brushed motor controllers, some less-powerful examples of which are shown below, can drive as much as 100~200A continuous, which is HUGE.
Just buy a Radio Control (RC) brushed ESC and feed it a servo PWM signal via the Arduino servo library, NOT a true PWM signal with analogWrite()!
You give it a servo signal, and it generates the low-level PWM to the motor automatically using its internal microcontroller and MOSFET driver circuitry, usually on the order of 8kHz~16kHz PWM output frequency. Many of these types of ESCs use the ATmega168 mcu internally.
For a single-direction ESC, such as for RC airplanes, a microsecond servo value between 700~1300us is 0% throttle, and a microsecond servo value between 1700~2100us is 100% throttle.
For a dual-direction ESC, such as for RC cars, with both forward and reverse, a microsecond value of ~1500us is 0% throttle, with ~2000us or so being 100% forward throttle and ~1000us or so being 100% reverse throttle.
Sample code:
#include <Servo.h>
Servo brushed_motor;
void setup()
{
brushed_motor.attach(9); // pin 9
// ~0% throttle (0% output PWM duty cycle), depending on ESC
// calibration, and assuming a forward-only ESC for RC airplanes
brushed_motor.writeMicroseconds(1000);
delay(2000);
// ~100% throttle (100% output PWM duty cycle), depending on ESC
// calibration, and assuming a forward-only ESC for RC airplanes
brushed_motor.writeMicroseconds(2000);
}
void loop()
{
// whatever you need here
}
To calibrate one of these ESCs to whatever throttle values you want, just set it to 2000us (full throttle) BEFORE you turn it on (careful--just in case it decides to go full throttle instead), then power it up, and it will register that as "full throttle". Next, withOUT powering it off, set it to 1000us (0% throttle), and it will register that as 0% throttle. Now, it is calibrated to have 1000us be 0% throttle and 2000us to be 100% throttle. If using an RC car brushed ESC instead of an RC airplane brushed ESC, you may have to play with it, do some research, and read its manual to get what you want, since 1500us might be considered 0% throttle, with 2000us being 100% forward throttle and 1000us being 100% reverse throttle. So, do the research.
In either case, here's some brushed RC ESCs which can drive motors and blowers or whatever just fine too.
These are just a couple examples. RC ESCs like these are designed to be really high power for high-end RC vehicles which can go up to 25~100mph sometimes, and be quite large. Do some research. Brushed RC ESCs are sold in many places. HobbyKing has the best prices in the industry for these types of things, with generally good to very-good quality parts.
H bridge is a fancy word for couple of BJTs. No, "H-bridge" is a very specific word to mean 4 transistors arranged in two complementary high-side + low-side pairs, allowing dual-driving 1 bidirectional 2-wire motor or speaker, or 2 separate unidirectional 2-wire motors or two single-driven speakers. An H-bridge can be designed with either MOSFETs or BJTs, so it implies nothing about being made with BJTs. Motors are driven usually with 8kHz to 16Khz PWM frequencies, rarely ever above 100kHz due to H-bridge limitations and motor inefficiencies/losses which increase with PWM frequency.
Oct 13, 2020 at 15:08
and a low powered option is suitable as it only requires a PWM signal to control the speed the rest is done with its on-board controller - no more than a 0.5mA signal is required. H bridge do not have discharge transistor. Do you know what a discharge transistor? It is a PNP for an NPN or vice versa that only becomes ON when the power transistor is OFF.