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Bidirectional H-Bridge DC-Motor Motion Controller
 
Bidirectional H-Bridge DC-Motor Motion Controller


 

Bidirectional H-Bridge DC-Motor Motion Controller

 


In applications requiring absolute accuracy in the speed control of dc servo motors, there’s no substitute for the traditional tachometer-based feedback loop. But for somewhat less demanding situations, adequate accuracy often can be achieved without the complication and expense of a tach. This can be done by taking advantage of the built-in electromechanical constants of the motor itself.


For example, the fact that every permanent-magnet dc motor exhibits a stable relationship between rpm and armature back-EMF implies that a reasonable job of constant-speed operation can be accomplished merely by driving the motor from a well-regulated voltage supply.

Even better speed regulation, sometimes rivaling tachometer feedback, can be achieved by adding a armature current, to the motor drive voltage. If this term is trimmed to accurately cancel armature resistance equal to motor-rated-voltage/lockedrotor-stall-current, the motor rpm will remain nearly constant over a wide range of loads. Although armature resistance cancellation via positive current feedback is hardly a new idea, the circuit described here gives it a novel twist by combining this trick with a motion-reversing H-bridge circuit topology.

The circuit works as follows: A speed-set point control voltage is produced by multi-turn precision potentiometer R3, acting in concert with VR1’s 1.25-V reference voltage. The resulting 0-0.75 V is scaled by a factor of 16 by op-amp A1 to produce a 0-12 V no-load M1 target armature voltage.

Speed-stabilizing, current-proportional positive feedback comes from current-sensing R1, is attenuated by R2, and summed by A1 with the speed-set point voltage. Optimum adjustment of R2 can produce almost perfect cancellation of M1’s parasitic resistance, resulting in a very “stiff” torque-versus-rpm characteristic. Motor speed-control performance will therefore be nearly independent of mechanical loading up to the voltage limit of the drive circuit.

The regulation of the motor drive in response to the composite control signal output by A1 (speed-setpoint plus current-feedback) is the job of either differential amplifier A3 or A4. It depends on the desired motor drive polarity and consequent direction of rotation as indicated by the state of direction-control flip-flop A2. For positive (clockwise) rotation, A2’s output is low and A4 is in control. This occurs because A3’s low output turns on Q3, which pulls Q5’s gate high, grounding the negative M1 connection via R1. Meanwhile, the same Q3 voltage applied to A3’s positive input causes A3 to rail Q6’s gate positive, holding the p-channel FET off. This prevents the possibility of “shoot-through” conduction between Q5 and Q6. A4 then can accurately sense, via the R5-R6-R7-R8-R9 differential network, the voltage applied to M1 and regulate it via power MOSFET Q4.

Thus, M1 is forced to run at the speed set by R2 until optical retro sensor E2/Q2 senses the arrival of the mechanical load at its clockwise limit. Light reflected into Q2 results in conduction, which overcomes the detection threshold set by feedback pot R4.This pulls A2’s positive input high and toggles the state of the direction control flip-flop. The resulting positive excursion of A2’s output turns on Q7 and forward-biases D1, disabling the A4/Q4 control loop.

Meanwhile, Q3 turns off, releasing Q5 and A3. This results in reversal the motor drive polarity and the initiation of speed-regulated counterclockwise motion. The motor will now continue to run counterclockwise until retro-sensor E1/Q1 senses the arrival of the mechanical load at the counterclockwise limit. Bridge polarity will consequently toggle again, causing the motor to reverse again and so forth ad infinitum (or at least until power is removed!).





Accurate LC Meter Capacitance Inductance Meter with 16F628 and LCD
Volt Ampere Meter with 16F876 Microcontroller and LCD display
 
Accurate LC Meter

Build your own Accurate LC Meter (Capacitance Inductance Meter) and start making your own coils and inductors. This LC Meter allows to measure incredibly small inductances making it perfect tool for making all types of RF coils and inductors. LC Meter can measure inductances starting from 10nH - 1000nH, 1uH - 1000uH, 1mH - 100mH and capacitances from 0.1pF up to 900nF. The circuit includes an auto ranging as well as reset switch and produces very accurate and stable readings.
PIC Volt Ampere Meter

Volt Ampere Meter measures voltage of 0-70V or 0-500V with 100mV resolution and current consumption 0-10A or more with 10mA resolution. The meter is a perfect addition to any power supply, battery chargers and other electronic projects where voltage and current must be monitored. The meter uses PIC16F876A microcontroller with 16x2 backlighted LCD.

50MHz 60MHz Frequency Meter / Counter with 16F628 & LCD
1Hz - 2MHz XR2206 Function Generator
60MHz Frequency Meter / Counter

Frequency Meter / Counter measures frequency from 10Hz to 60MHz with 10Hz resolution. It is a very useful bench test equipment for testing and finding out the frequency of various devices with unknown frequency such as oscillators, radio receivers, transmitters, function generators, crystals, etc.
1Hz - 2MHz XR2206 Function Generator

1Hz - 2MHz XR2206 Function Generator produces high quality sine, square and triangle waveforms of high-stability and accuracy. The output waveforms can be both amplitude and frequency modulated. Output of 1Hz - 2MHz XR2206 Function Generator can be connected directly to 60MHz Counter for setting precise frequency output.

BA1404 HI-FI Stereo FM Transmitter
USB IO Board PIC18F2455 / PIC18F2550
BA1404 HI-FI Stereo FM Transmitter

Be "On Air" with your own radio station! BA1404 HI-FI Stereo FM Transmitter broadcasts high quality stereo signal in 88MHz - 108MHz FM band. It can be connected to any type of stereo audio source such as iPod, Computer, Laptop, CD Player, Walkman, Television, Satellite Receiver, Tape Deck or other stereo system to transmit stereo sound with excellent clarity throughout your home, office, yard or camp ground.
USB IO Board

USB IO Board is a tiny spectacular little development board / parallel port replacement featuring PIC18F2455/PIC18F2550 microcontroller. USB IO Board is compatible with Windows / Mac OSX / Linux computers. When attached to Windows IO board will show up as RS232 COM port. You can control 16 individual microcontroller I/O pins by sending simple serial commands. USB IO Board is self-powered by USB port and can provide up to 500mA for electronic projects. USB IO Board is breadboard compatible.

ESR Meter / Transistor Tester Kit
Audiophile Headphone Amplifier Kit
 
ESR Meter / Capacitance / Inductance / Transistor Tester Kit

ESR Meter kit is an amazing multimeter that measures ESR values, capacitance (100pF - 20,000uF), inductance, resistance (0.1 Ohm - 20 MOhm), tests many different types of transistors such as NPN, PNP, FETs, MOSFETs, Thyristors, SCRs, Triacs and many types of diodes. It also analyzes transistor's characteristics such as voltage and gain. It is an irreplaceable tool for troubleshooting and repairing electronic equipment by determining performance and health of electrolytic capacitors. Unlike other ESR Meters that only measure ESR value this one measures capacitor's ESR value as well as its capacitance all at the same time.
Audiophile Headphone Amplifier Kit

Audiophile headphone amplifier kit includes high quality audio grade components such as Burr Brown OPA2134 opamp, ALPS volume control potentiometer, Ti TLE2426 rail splitter, Ultra-Low ESR 220uF/25V Panasonic FM filtering capacitors, High quality WIMA input and decoupling capacitors and Vishay Dale resistors. 8-DIP machined IC socket allows to swap OPA2134 with many other dual opamp chips such as OPA2132, OPA2227, OPA2228, dual OPA132, OPA627, etc. Headphone amplifier is small enough to fit in Altoids tin box, and thanks to low power consumption may be supplied from a single 9V battery.
 

Arduino Prototype Kit
RF Remote Control 433MHz Four Channel
 
Arduino Prototype Kit

Arduino Prototype is a spectacular development board fully compatible with Arduino Pro. It's breadboard compatible so it can be plugged into a breadboard for quick prototyping, and it has VCC & GND power pins available on both sides of PCB. It's small, power efficient, yet customizable through onboard 2 x 7 perfboard that can be used for connecting various sensors and connectors. Arduino Prototype uses all standard through-hole components for easy construction, two of which are hidden underneath IC socket. Board features 28-PIN DIP IC socket, user replaceable ATmega328 microcontroller flashed with Arduino bootloader, 16MHz crystal resonator and a reset switch. It has 14 digital input/output pins (0-13) of which 6 can be used as PWM outputs and 6 analog inputs (A0-A5). Arduino sketches are uploaded through any USB-Serial adapter connected to 6-PIN ICSP female header. Board is supplied by 2-5V voltage and may be powered by a battery such as Lithium Ion cell, two AA cells, external power supply or USB power adapter.
200m 4-Channel 433MHz Wireless RF Remote Control

Having the ability to control various appliances inside or outside of your house wirelessly is a huge convenience, and can make your life much easier and fun. RF remote control provides long range of up to 200m / 650ft and can find many uses for controlling different devices, and it works even through the walls. You can control lights, fans, AC system, computer, printer, amplifier, robots, garage door, security systems, motor-driven curtains, motorized window blinds, door locks, sprinklers, motorized projection screens and anything else you can think of.
 

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