Here is a Simple Motor Speed Regulator Circuit made to control the speed of DC powered PCB drills.
When drilling printed circuit boards, it is really important to manage the speed carefully to make sure the holes are clean and in the right spots.
The main part of this circuit is the LM3578 which has special feedback inputs and a 1V internal reference voltage.
It also includes an oscillator circuit.
This speed control circuit works by using the LM3578 along with an IRF540 MOSFET to adjust the motors speed.
The design is meant to provide smooth and adjustable speed control for small PCB drilling machines.
Remember the supply voltage can be between 6 to 30V DC and you should pick a voltage that matches the drill motors requirements.
Circuit Working:
Parts List:
| Component Type | Value/Part Number | Quantity |
|---|---|---|
| Resistors | 120k | 1 |
| 100k | 1 | |
| 4.7k | 1 | |
| Potentiometer | 220k | 1 |
| Capacitors | Ceramic 22pF | 1 |
| Ceramic 0.1µF | 1 | |
| Electrolytic 470µF 50V | 1 | |
| Semiconductors | IC LM3578 | 1 |
| MOSFET IRF540 | 1 | |
| Diode 1N4007 | 1 | |
| Other | PCB Drill Motor | 1 |
The design of the circuit mainly focuses on the IC LM3578 switching regulator chip, which creates a Pulse Width Modulation PWM signal to control how fast the motor runs.
In this design a MOSFET IRF540 acts like a switch carefully managing the electrical power sent to the motor.
The resistors R1, R2 and VR1 are important because they help set the reference voltage and also affect the oscillators frequency working together with capacitor C1.
Capacitor C2 is added to make the circuit more stable.
When it comes to generating PWM and controlling the motor the LM3578 is really good at making a PWM signal based on feedback from the system.
The IRF540 MOSFET quickly turns on and off which helps control how much power goes to the motor.
Diode D1 is crucial because it protects the circuit from damage caused by back electromotive force EMF.
To adjust the speed, the circuit has a variable resistor VR1 potentiometer that lets users change the motors speed to fit their needs.
Capacitor C3 which is used to filter the power supply making sure the circuit runs smoothly and reliably.
Resistor R3 helps the MOSFET work properly by pulling its gate down to a low state when the LM3578 output is also low.
This stops any floating issues and makes the circuit work better.
Formulas with Calculations:
Below mentioned are the formulas with calculations for Simple Motor Speed Regulator Circuit for PCB Drills:
The oscillation frequency of LM3578 is determined by:
f = 1 / (R3 × C1 × 1.3)
- f is the oscillation frequency of LM3578
- R3 is 100k in the circuit
- C1 is the 22pF in the circuit
For the given values:
f = 1 / (100k × 22pF × 1.3) = 348 kHz
The duty cycle of the PWM signal is controlled by the feedback and resistor network, which determines the motor speed.
How to Build:
To build a Simple Motor Speed Regulator Circuit for PCB Drills following steps are required to follow:
- Assemble all the components as mentioned in the above circuit diagram
- Connect pin 1 of IC1 to the junction of one end of resistor R2 and and one end of capacitor C1
- Connect pin 2 of IC1 to one end of resistor R1 and other end of resistor R1 connect to one of VR1 and other end of VR1 connect to GND.
- Connect pin 3 of IC1 to the junction of other end of resistor R2 and and other end of capacitor C1
- Connect capacitor C2 from pin 3 of IC1 and GND
- Connect pin 4 of IC1 to GND of the circuit
- Connect pin 5 of IC1 to the GATE of MOSFET Q1
- Connect resistor R3 from pin 5 of IC1 to GND.
- Connect pin 6, pin7, and pin 8 of IC1 to positive supply of 6V to 30V DC.
- Connect PCB Drill Motor one end to positive supply terminal and other end of drill to DRAIN pin of Q1 MOSFET.
- Connect diode D1 from positive supply terminal to between DRAIN pin and PCB Drill Motor pin
- Connect SOURCE pin of MOSFET Q1 to GND.
- Connect positive of capacitor C3 to positive supply terminal and negative of capacitor connect to GND
Conclusion:
This easy to use Simple Motor Speed Regulator Circuit for PCB Drills helps you adjust the speed of PCB drilling motors accurately.
It uses PWM control, which makes it work efficiently and keeps heat and power loss low.
The combination of the LM3578 and IRF540 makes it a dependable choice for controlling the speed of small motors.