I needed to make a speed controller for the propeller. To blow off the smoke from the soldering iron, and ventilate the face of the face. Well, for fun, put everything at the minimum cost. The easiest way is a low-power DC motor, of course, to regulate variable resistor, but to find a resume for such a small denomination, and even the required power, you have to try hard, and it will obviously cost more than ten rubles. Therefore, our choice is PWM + MOSFET.

I took the key IRF630. Why this one MOSFET? Yes, I just got about ten of them from somewhere. So I use it, so you can put something less overall and low-power. Because the current here is unlikely to be more than an ampere, and IRF630 able to drag through itself under 9A. But it will be possible to make a whole cascade of fans by connecting them to one twist - enough power :)

Now it's time to think about what we'll do PWM. The thought immediately suggests itself - a microcontroller. Take some Tiny12 and do it on it. I dismissed this thought instantly.

1. Spending such a valuable and expensive part on some kind of fan is disgusting to me. I will find a more interesting task for the microcontroller
2. Another software for this to write, doubly zapadlo.
3. The supply voltage is 12 volts there, lowering it to power the MK to 5 volts is generally already lazy
4. IRF630 will not open from 5 volts, so here you would also have to install a transistor so that it supplies a high potential to the gate of the field worker. Nafig nafig.

Operational amplifiers can be discarded immediately. The fact is that for a general-purpose op-amp, after 8-10 kHz, as a rule, limiting output voltage begins to collapse sharply, and we need to jerk the field worker. Yes, even at a supersonic frequency, so as not to squeak.

Comparators remain, they do not have the ability of the opamp to smoothly change the output voltage, they can only compare two voltages and close the output transistor based on the results of the comparison, but they do it quickly and without blocking the characteristic. I rummaged through the barrels and did not find any comparators. Ambush! More precisely was LM339, but it was in a large case, and religion does not allow me to solder a microcircuit for more than 8 legs for such a simple task. It was also too much to drag into the storehouse. What to do?

And then I remembered such a wonderful thing as analog timer - NE555. It is a kind of generator, where you can set the frequency, as well as the duration of the pulse and pause, with a combination of resistors and a capacitor. How much different crap has been done on this timer, over its more than thirty-year history ... Until now, this microcircuit, despite its venerable age, is stamped in millions of copies and is available in almost every store at a price of a few rubles. With us, for example, it costs about 5 rubles. Rummaged through the bottom of the barrel and found a couple of pieces. O! Right now and stir up.

How it works
If you do not delve deeply into the structure of the 555 timer, then it is not difficult. Roughly speaking, the timer monitors the voltage on the capacitor C1, which removes from the output THR(THRESHOLD - threshold). As soon as it reaches the maximum (the conder is charged), the internal transistor opens. which closes the output DIS(DISCHARGE - discharge) to the ground. At the same time, at the output OUT a logical zero appears. The capacitor begins to discharge after DIS and when the voltage on it becomes equal to zero (full discharge), the system will switch to the opposite state - at output 1, the transistor is closed. The capacitor starts to charge again and everything repeats again.
The charge of the capacitor C1 follows the path: " R4->upper arm R1 ->D2", and the discharge along the way: D1 -> lower arm R1 -> DIS. When we turn the variable resistor R1, then we change the ratio of the resistances of the upper and lower arms. Which, accordingly, changes the ratio of the pulse length to the pause.
The frequency is set mainly by the capacitor C1 and also depends a little on the value of the resistance R1.
Resistor R3 provides a pull-up output to a high level - so there is an open collector output. Which is not able to set a high level on its own.

Diodes can be installed completely, conders of about the same value, deviations within one order of magnitude do not particularly affect the quality of work. At 4.7 nanofarads set in C1, for example, the frequency drops to 18 kHz, but it is almost inaudible, it seems that my hearing is no longer perfect :(

I dug into the bins, which itself calculates the operating parameters of the NE555 timer and assembled the circuit from there, for an astable mode with a duty cycle of less than 50%, but instead of R1 and R2 I screwed in a variable resistor, which changed the duty cycle of the output signal. It is only necessary to pay attention to the fact that the output DIS (DISCHARGE) through the internal key of the timer connected to ground, so it was impossible to plant it directly to the potentiometer, because when the regulator is turned to the extreme position, this output would sit on Vcc. And when the transistor opens, there will be a natural short circuit and a timer with a beautiful puff will emit magic smoke, on which, as you know, all electronics work. As soon as the smoke leaves the microcircuit, it stops working. That's how it is. Therefore, we take and add another resistor per kilo-ohm. It will not make the weather in regulation, but it will protect it from burnout.

No sooner said than done. Etched the board, soldered the components:

Everything is simple below.
Here I am attaching a signet, in my dear Sprint Layout -

And this is the voltage on the engine. You can see a small transition process. It is necessary to put the conder in parallel on the floor of the microfarad and smooth it out.

As you can see, the frequency floats - it’s understandable, because our operating frequency depends on the resistors and the capacitor, and since they change, the frequency floats, but it doesn’t matter. In the entire range of regulation, it never fits into the audible range. And the whole construction cost 35 rubles, not counting the body. So - Profit!

A Pulse Width Modulation based regulator circuit, or simply, can be used to change the speed of a DC motor by 12 volts. Shaft speed control with PWM gives better performance than using simple change DC voltage supplied to the motor.

PWM motor speed controller

Motor connected to field effect transistor VT1, which is controlled by a PWM multivibrator built on the popular NE555 timer. Due to the application, the speed control scheme turned out to be quite simple.

As already mentioned above, PWM motor speed controller done with simple generator pulses generated by an unstable multivibrator with a frequency of 50 Hz performed on the NE555 timer. Multivibrator output signals provide gate bias MOSFET transistor.

The duration of the positive pulse can be adjusted with a variable resistor R2. The larger the positive pulse width of the MOSFET gate, the more power is delivered to the DC motor. And vice versa, the narrower its width, the less power is transmitted and, as a result, the engine speed. This circuit can be operated from a 12 volt power supply.

Characteristics of the transistor VT1 (BUZ11):

• Transistor type: MOSFET
• Polarity: N
• Maximum power dissipation (W): 75
• Ultimately allowable voltage drain-source (V): 50
• Maximum allowable gate-source voltage (V): 20
• Maximum allowable D.C. drain (A): 30