Showing posts with label 10. Show all posts
Showing posts with label 10. Show all posts
Monday, September 23, 2013
zBot 10 A Power Stage for DC Motor
If you look at the chassis of the zBot vehicle1, you’ll find two parts requiring intelligent control: the steering servo and the DC motor. The so called H-bridge is the normal circuit for electronic control of revolution speed and direction. The DC motor of a Tamiya car is powerful enough to propel zBot at up to 20 miles per hour.
The motor then consumes more than 10 A, so we choose high-current power MOSFETs for the driver stage. There are lots of different devices to choose from. The MOSFET we require has to supply the maximum motor current and, importantly, it has to be switched with gate voltages of about 5 V. In this case, the microcontroller switches the power stage (‘low side’) directly. For high side driving level shifters are necessary. The schematic of the H-bridge power stage shows a few inverters, NAND gates and two tri-stateable drivers. These logic functions are very important as the easier way, i.e.., directly controlling all four MOSFET has a fatal disadvantage.
In case of a software crash it could happen that two ore more MOSFETs are switched on incor-rectly for exam-ple, T4 and T7. In that case, the current through the transistors is limited by the internal resistors of the MOSFETs (about 10 mO) only. Such a fatal error would destroy the MOSFETs. The logic functions configured here effectively avoid illegal states.To control the DC motor, three signals are needed: DIR, PWM and STOP. DIR controls the direction of the motor revolution, PWM the speed, and STOP brakes the motor.
The software module for the DC motor is called dcm.c.(070172-I) The complete document called Zbot the Robot Experimental Platform is available for free downloading from the Elektor Electronics website. The file number is 070172-11.zip (July/August 2007).
Author: Jens Altenburg Copyright: Elektor
Saturday, April 6, 2013
10 W Audio Amplifier Rise
This audio amplifier project is a class AB audio power amplifier using a TDA2003 module power amplifier.It is simple to construct and has only a few outside parts. The module is designed with short circuit and thermal protection. It can drive lots as low as one.6 ohm and can delivering-over ten watts from a 16 V DC power supply. Figure one shows the TDA 2003 packaged and pin configuration.
The power supply ought to be well filtered to reduce mains hum, the on board capacitors alone are not adequate for this purpose but are necessary to make sure stability. Additional filtering is unnecessary if operating from a battery. If boards are used for stereo, you will need to double the size of the power supply.
The power supply necessary for is 8 - 18V DC at one Amp or more. Maximum output power will only be obtained with a power supply of greater than 1A at 16V DC, and using two ohm speakers (or two by four ohm speakers in parallel). However about 4W RMS can be obtained with a 12V DC, 1A supply in to a four ohm load.
The power supply necessary for is 8 - 18V DC at one Amp or more. Maximum output power will only be obtained with a power supply of greater than 1A at 16V DC, and using two ohm speakers (or two by four ohm speakers in parallel). However about 4W RMS can be obtained with a 12V DC, 1A supply in to a four ohm load.
Audio Amplifier Circuit Diagram
The major circuitry is contained in the amplifier module. C1 is the-input coupling capacitor & blocks DC signal, so does C3 which is the output coupling capacitor, & C2which blocks DC from the feed back loop to the differential input. R2 & R3 set the level of feedback. C4 & R4 provide a high frequency load for stability where loudspeaker inductive reactant may become excessive. C5 & C6 provide power supply filtering.
There ought to be no issues with the stability of the circuit, however in the event you do, make definite the power-supply filtering and leads are adequate. If necessary you might connect an RC compensation network-between IC pins two and four as in the knowledge sheet. Values for Cx of 22 - 33 nF and for Rx of 39 - 47 ohms,should be satisfactory whilst still maintaining satisfactory high frequency response.
The gain is equal to one + (R2/R3) = 101, or 40 dB, minus any input attenuation. You may reduce the-overall gain by increasing the worth of R3 in the event you are only able to make use of part of the potentiometer range as a volume control. For example, an R3 of ten ohms will give a gain of 23 (27dB).
Subscribe to:
Posts (Atom)
