This page was generated from an open-source design by DutchBrewer. You can find the original project here, and read the license here.
PWM Speed Controller
This is a low cost project is based on the Dial-a-Speed design. This is a pulse-width modulation (PWM) speed controller, using a 555 timer IC wired in astable mode to control an N-channel power-enhancement MOSFET that actually switches the motor on and off. This circuit is cleverly designed to offer a wide range of control, and can produce square waves with duty cycles ranging from less than 5% to more than 95%, depending on where you set the dial.
I originally built the design exactly as shown in the Make article however I found all of the jumpers required on the board left the design rather messy. I opted to design a board for this project so I could just solder on the components and forget about all of the jumper wires.I am using the PWM to control the speed of a small DC motor that spins a magnet for a stir plate.
The schematic for this design can be seen in the Make Magazine Dial a Speed article, and the background details of the circuit can be found on the Dallas Personal Robotics Group page.
Parts list: (a slightly modified list from the Make Article)
- Circuit board based on this design
-
100K audio-taper potentiometer RadioShack #271-1722 (R1)
-
1N4001 micro 1A diode (3) RadioShack #276-1101 (D1, D2, D3,)
-
MOSFET IRF510 transistor RadioShack #276-2072 (Q1)
-
TO-220/TO-202 aluminum heat sink RadioShack #276-1368 (Mounted to Q1)
-
555 timer chip RadioShack #276-1723 (U1)
-
2-position PC board terminals (2) RadioShack #276-1388 (J1, J2, J3, J4)
-
100μF axial-lead electrolytic capacitor, 35V 20% RadioShack #272-1016 (C1)
-
0.1μF ceramic disc capacitor (2) RadioShack #272-135 (C3, C4)
-
10K resistor, 1/8W RadioShack #271-006 (R2)
- Silver tone knurled knob RadioShack #274-424 (Mounted to R1)
- Project Enclosure RadioShack 270-1805 (This is the enclolsure I used something different might work better for you)
Procedure:
- Procure circuit board
- Procure components
- Solder components to PCB
- Connect J1 to 5-12 VDC Power Supply
- Connect J2 to Load (DC motor, LED, etc)
- Connect potentiometer (R1) to J3 and J4
- Adjust potentiometer to enjoy variable speed intensity ect.
Bill of materials
Connected nets
All points in a row of the nets table are connected by wires.| Circuit node | Connected pins |
|---|---|
| Net 1 | |
| Net 2 | |
| Net 3 | |
| Net 4 | |
| Net 5 | |
| Net 6 | |
| Net 7 | |
| Net 8 | |
| Net 9 |
Detailed part info
Rectifier Diode
A standard rectifier diode
555 Timer
The classic 555 general purpose timer/oscillator.
Pin descriptions
| Pin | Description |
|---|---|
| 4 | Reset |
| 5 | Control Voltage |
| 6 | Threshold |
| 7 | Discharge |
| 8 | +Vcc Supply Voltage |
| 1 | Ground |
| 2 | Trigger |
| 3 | Output |
Resistor (resistance 10kΩ, power 0.25W)
A generic resistor (0.25W)
Electrolytic Capacitor (capacitance 0.1mF, voltage 35V)
A generic capacitor
Basic FET N-Channel
A MOSFET N-Channel Transistor
Rotary Potentiometer (Large) (maximum resistance 100kΩ)
A rotary adjustable resistor (potentiometer).
Pin descriptions
| Pin | Description |
|---|---|
| 1 | leg1 |
| wiper | wiper |
| 2 | leg2 |
Screw terminal (part number 276-1388, pins 2, pin spacing 5.0mm)
Generic screw terminal
Screw terminal (part number 276-1388, pins 2, pin spacing 5.0mm)
Generic screw terminal
Ceramic Capacitor (capacitance 100nF, voltage 50V)
A generic capacitor
Ceramic Capacitor (capacitance 100 nF, voltage 50V)
A generic capacitor