Low voltage DC motor speed control circuit
Description.
Here is the circuit diagram of a low voltage /low power DC motor speed controller based on the IC TDA 7274 from ST Microelectronics. The IC TDA 7274 is a monolithic integrated DC motor speed controller intended for low voltage/ low power applications. Built in internal voltage reference voltage, wide input voltage range (1.8 t0 6V), high linearity, 700mA output current, excellent temperature stability etc make this IC well suitable for almost all low power DC motor speed control applications.
The motor to be controlled is connected between pin3 (Vs) and pin4 (output) of the IC. Resistor network comprising of R1, R2, and R3 is the section that deals with the speed control. Control pin (pin8) of the IC is connected to the junction of R2 and R3 and the speed of the motor varies linearly according to the position of POT R3. Capacitor C1 rectifies the fluctuations in motor speed and capacitor C2 cancels the motor spikes.
Circuit diagram.
Notes.
- The circuit can be assembled on a Perf board.
- Power supply Vs can be anything between 1.8V to 6V and it must be selected according to the rating s of the motor.
- Maximum output current capacity of this circuit is 700mA.
- TDA7274 must be mounted on a holder.
- POT R3 can be used to vary the motor speed.
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please someone help me out i wana make an IR-remote operated DC motor, soo that I can control its speed remotely…
Sam,
I can help, please contact me by mail sayang zonnet nl
i m looking for a circuit that can control dc motor speed and its direction of rotation and also i want to display the speed of the motor..plz help me m really worried about my project to be submitted very soon…
please post the explanation of the current flow on this circuit and how this circuit operates….
Hi Jay use TDA7275A which will be most suited for 12 volt DC brush type motor application
http://www.digchip.com/datasheets/parts/datasheet/456/TDA7275A-pdf.php
give a circuit which would run the motor at (say —30%, 60%, 100% )of the maximum speed of motor……using only 12V, 1A supply transformed through 230V, 5A…
switches are needed to switch to different speeds..
a very very thanks in advance….!
Thanks for the circuit? Can I include a DPDT switch in this for a reversible motor?
Many thanks in advance
Al
Hi Rolfi,
I have sent you a personal mail. Please check it.
The TDA7274 was intended mainly for portable music players, and however ingenious, together with cassette players and the like, it has been discontinued and is obsolete (See manufacturers data/application sheets: http://www.st.com/stonline/products/literature/od/1481/tda7274.pdf)
As a general comment, though, I would like to mention that speed control of a DC motor connected to a varying load can be tricky. A stable voltage is not enough, because when a load is applied, the speed will decrease, – while the armature current increases. In order to avoid this decrease in speed, the presence of a speed regulator will increase the motor voltage enough to keep the speed virtually constant.
Now, for this, two different strategies exist:
1. Measuring speed and applying voltage until the speed is ”correct” (Negative Feedback control).
2. Measuring the armature current, which reflects the decrease in speed, and increase the voltage proportionally (Feedforward control).
The latter is the simplest and cheapest, and that is mainly what the TDA7274 does, – or did.. However, the problem here is that to much compensation will make the motor run faster, thus making the system unstable. Moreover, this type of compensation lacks the accuracy of the negative Feedback method, and it also depends heavily on the electromechanical properties of the individual motor. In the circuit diagram, R1 determines this compensation, it’s optimal value being dependent of the motor in question. A too big value will inevitably lead to instability.
Today, in applications where speed control is essential, small motors will often be step motors, whose speed is genuinely determined by the frequency of the applied pulses, while PWM (pulse width modulation) is used for controlling the applied voltages. For a step motor, even the shaft position is easily controlled. Disk drives rely on this.
I like it…………