Micro drill speed controller circuit

Very often when working and drilling holes in the board, we either put the microdrill down, then pick it up again and continue drilling. But often the engines heat up at high speeds, and it’s harder to pick it up.

Due to vibration, it can often slip off the board and create a cable. For these purposes, I suggest assembling DIY speed controller.

The principle of operation is as follows: when the load is small, then a small current passes and the speed is reduced, as soon as the load increases, the speed increases.

Device diagram:

A huge advantage of the device is that the engine runs in a lighter mode and the contact brushes wear out less.

This is the main answer to the question how to make the speed increase when drilling

Printed circuit board

Radio components for the regulator

The LM317 chip must be installed on a radiator to avoid overheating. No cooler installation required
Electrolytic capacitors with a rated voltage of 16V.
1N4007 diodes can be replaced with any other ones rated for a current of at least 1A.
LED AL307 any other. The printed circuit board is made on single-sided fiberglass.
Resistor R5 with a power of at least 2W, or wirewound.

The power supply must have a current reserve for a voltage of 12V. The regulator is operational at a voltage of 12-30V, but above 14V you will have to replace the capacitors with ones corresponding to the voltage.
The finished device starts working immediately after assembly.

Setting up and little things at work

Resistor P1 sets the required idle speed. Resistor P2 is used to set the sensitivity to the load; we use it to select the desired moment of increasing speed. If you increase the capacitance of capacitor C4, the delay time at high speeds will increase or if the engine runs jerkily.
I increased the capacitance to 47uF.
The engine is not critical for the device. It just needs to be in good condition.
I suffered for a long time, I already thought that the circuit had a glitch, that it was unclear how it regulates the speed, or reduces the speed during drilling.
But I disassembled the engine, cleaned the commutator, sharpened the graphite brushes, lubricated the bearings, and reassembled it.
Installed spark arresting capacitors. The scheme worked great.
Now you don't need an inconvenient switch on the micro drill body.

Regulators for manual drilling of circuit boards.

Greetings radio amateurs. And don't let your soldering iron cool down. In principle, the Internet is full of different regulator circuits, choose according to your taste, but so as not to suffer for a long time in searching, we decided to bring to your attention several circuit options in one article. Let’s make a reservation right away that we will not describe the operating principle of each circuit; you will be provided with a circuit diagram of the regulator, as well as a printed circuit board for it in LAY6 format. So, let's begin.

The first version of the regulator is built on the LM393AN microcircuit, power is supplied to it from the 78L08 integrated stabilizer, the op-amp controls a field-effect transistor, the load of which is the motor of a hand-held mini drill. Schematic diagram:

The speed is adjusted using potentiometer R6.
Supply voltage 18 Volts.

The LAY6 format board for the LM393 circuit looks like this:

Photo view of the LAY6 format board:

Board size 43 x 43 mm.

The pinout of the IRF3205 field effect transistor is shown in the following figure:

The second option is quite widespread. It is based on the principle of pulse width regulation. The circuit is based on the NE555 timer chip. Control pulses from the generator are sent to the field gate. Transistors IRF510...640 can be installed in the circuit. Supply voltage 12 Volts. Schematic diagram:

The engine speed is adjusted by variable resistor R2.
The pinout of IRF510...640 is the same as that of IRF3205, picture above.

The LAY6 format printed circuit board for the NE555 circuit looks like this:

Photo view of the LAY6 format board:

Board size 20 x 50 mm.

The third version of the speed controller circuit is no less popular among radio amateurs than PWM; its distinctive feature is that the speed control occurs automatically and depends on the load on the motor shaft. That is, if the engine is spinning at idle, its rotation speed is minimal. When the load on the shaft increases (at the time of drilling a hole), the speed automatically increases. This diagram can be found on the Internet by searching for “Savov regulator”. Schematic diagram of an automatic speed controller:

After assembly, it is necessary to make a small adjustment of the regulator; for this, at idle speed of the motor, trimming resistor P1 is adjusted so that the speed is minimal, but so that the shaft rotates without jerking. P2 serves to adjust the sensitivity of the regulator to an increase in the load on the shaft. With a 12-Volt power supply, install electrolytes at 16 Volts, 1N4007 are replaceable with similar ones from 1 Ampere, any LED, for example AL307B, LM317 can be placed on a small heat sink, the printed circuit board is designed for installing a radiator. Resistor R6 – 2 W. If the motor rotates jerkily, slightly increase the value of capacitor C5.

The circuit board of the automatic speed controller is shown below:

Photo view of the automatic speed controller board LAY6 format:

Board size 28 x 78 mm.

All of the above boards are made on one-sided foil fiberglass laminate.

You can download schematic diagrams of speed controllers for a hand mini-drill, as well as printed circuit boards in LAY6 format using a direct link from our website, which will appear after clicking on any line of the advertising block below except for the line “Paid advertising”. File size – 0.47 Mb.

Good afternoon. I present to your attention a regulator for picking printed circuit boards, the diagram is taken from Radio magazine for 2010. Assembled and tested - works great. There are no scarce parts in the circuit - only 4 common transistors and several passive radio elements that can be removed from any non-working equipment. Schematic diagram of the speed controller:

Operation of the mini drill regulator circuit

The elements vd1, vd2, r2, r3, vt1, r11 are used to assemble the idle speed regulator (hereinafter referred to as XO). Diode vd3 is a disconnector for the XO regulator and a current trigger assembled at vt2, r4, r7. Diode vd5 facilitates the temperature regime of current sensor r7. Capacitor C2 and resistor r6 ensure a smooth return to the XO mode. On vd4, r5, c1 there is a starting current limiter (i.e. soft start). The composite transistor formed by vt3 and vt4 amplifies the currents of the previous nodes. In parallel with the motor, it is imperative to turn on the protective diode vd6 in the opposite direction, so that the EMF arising in it does not burn the radio elements of the regulator.

All resistors except R7 are used at 0.125 W, R7 at 0.5 W. It is advisable to select resistance R7 individually for each motor so that the current trigger operates clearly at the right moment, i.e. the drill did not slip off the core and did not jam.

I am attaching a photo of the assembled mini-drill speed controller and the printed circuit board topology I laid out. Transistor P213 must be turned on exactly as it is written on the board with the name “p213” (due to the reverse diode).

By using planar components, the board can be reduced in size to the point where it fits inside (or outside) the drill. As an option, this speed controller can be used to control the speed of any DC electric motors - in toys, ventilation, etc. I wish everyone good luck. Sincerely, Andrey Zhdanov (Master665).

Every radio amateur had to drill technological holes in the substations, with professional or ordinary homemade mini-drills, and each of them broke drills only because they did not calculate the force of pressure on the drill, or did not stop the drill in time. And it also happens that motors fail when the voltage is exceeded and overheats, or it is impossible to hold it in your hands due to the high temperature of the motor. I think this happened not only to me, since in the magazine “Radio” for 2009, a circuit was published for controlling PPM motors. It was invented by S. Saglaev, Moscow. The logic of this circuit is simple, turn on the circuit - the motor spins slowly, we start drilling - the stroke increases, the speed increases (and a hole is created in the board). At the end of drilling, the engine stroke decreases and the speed decreases.

In principle, this circuit is universal and is suitable for all electric motors with an operating voltage of up to 30 volts (if you use a 30 volt motor, then you need to change the capacitor C2 to 40 volts with a margin).

For drilling, I use a 12-volt motor from a video camera, but I power the circuit with 20 volts, since I’m not afraid that the motor will fail, because the increased voltage is supplied to it through this control unit.

So, let's get to the essence of this circuit, there are no scarce radio elements in it, there are also only two transistors and a stabilizer on everyone's favorite KREN, and everything else is crumbly. You can refuse the diode bridge if the circuit is powered by constant voltage, I personally refused, but I left the capacitors C1 and C3 (I don’t know why).

Let's move on to assembling the circuit. Since I didn’t have transistor VT1, I replaced it with transistor KT814a. Those resistors marked * are adjusted to the motor; R1 sets the threshold of mechanical load on the electric motor for its full stroke. Resistor R2 sets the minimum open circuit voltage.

The printed circuit board I designed is not very small - you can make it smaller. Assembled device:

For idle speed I installed a trimming resistor. The motor itself is wrapped with electrical tape for ease of holding it in your hand. With the previous motor the circuit did not work correctly.

And here are the holes made with a mini drill controlled by this circuit.

Yes, this is my drill and for some reason everyone gets scared when they see it.
Well, I feel sorry for the money for a normal device.

The most enjoyable part of the job, and the most difficult, is drilling the circuit board. I'm assembling something new and I need to drill the whole thing.
Very often you have to put the drill on the table while you are thinking about something or your spouse is distracting you, and if there is also a creative mess on the table, then it is very difficult to find a place for micro drills. Due to vibration when turned on, it may fly off the table.

Then the idea arose to assemble a stabilizer with variable speed control.
I found a good selection of circuits on Radiokot:

Idea and scheme

I wanted to make sure that the microdrill had low revolutions at idle, and when loaded, the rotation speed of the drill increased.
Firstly, it is very convenient, secondly, the engine operates in a lighter mode, and thirdly, the brushes wear out less.

Image source radiokot.ru

And here is a diagram of such an automatic speed controller. Her author Alexander Savov from Bulgaria.

Details

The circuit uses easily accessible parts. The microcircuit must be installed on a radiator to avoid overheating.
Electrolytic capacitors with a rated voltage of 16V.
1N4007 diodes can be replaced with any other ones rated for a current of at least 1A.
LED AL307 any other. The printed circuit board is made on single-sided fiberglass.
Resistor R5 with a power of at least 2W, or wirewound.

The power supply must have a current reserve for a voltage of 12 V. The regulator is operational at a voltage of 12-30 V, but above 14 V you will have to replace the capacitors with ones corresponding to the voltage.

Setting up

The finished device starts working immediately after assembly. Resistor P1 sets the required idle speed. Resistor P2 is used to set the sensitivity to the load; we use it to select the desired moment of increasing speed. If you increase the capacitance of capacitor C4, the delay time at high speeds will increase or if the engine runs jerkily. I increased the capacitance to 47uF.

The engine is not critical for the device. It just needs to be in good condition.
I suffered for a long time, I already thought that the circuit had a glitch, that it was unclear how it regulates the speed, or reduces the speed during drilling.
But I disassembled the engine, cleaned the commutator, sharpened the graphite brushes, lubricated the bearings, and reassembled it.
Installed spark arresting capacitors. The scheme worked great.
Now you don't need an inconvenient switch on the micro drill body.

Printed circuit board in Sprint Layout

Wiring of the respected MP42B, pulled from the general file of his article mentioned at the beginning.

05/02/2019, at the request of the comrades, Igor Kotov signed the details on the board and spruced it up a little.
The archive has been updated.
▼ 🕗 05/02/19 ⚖️ 11.15 Kb ⇣ 19