Three in One Tester for Audio, Diode, and Circuit

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This electronic schematic circuit is a test circuit for audio, diode and circuit. This very handy simple solid state battery operated tester. It works on two 1.2-1.5 AA-batteries.





This three in one tester can be used for :
  • audit AF/LF signal
  • circuit tester
  • diode tester
  • 1 KHz tone generator
When you switch S1 OFF the diode/circuit testerschematic can be used.

Source: http://users.belgacom.net/hamradio/homebrew.htm

ATX Power Supply Connector-Pinouts Diagram

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Here's a standard for ATX Power supply connectors dan ATX power supply pinouts. Standard power supplies turn the incoming 110V or 220V AC (Alternating Current) into various DC (Direct Current) voltages suitable for powering the computer's components.


Power supplies are quoted as having a certain power output specified in Watts, a standard power supply would typically be able to deliver around 350 Watts.

The more components (hard drives, CD/DVD drives, tape drives, ventilation fans, etc) you have in your PC the greater the power required from the powersupply.

By using a PSU that delivers more power than required means it won't be running at full capacity, which can prolong life by reducing heat damage to the PSU's internal components during long periods of use.

Always replace a power supply with an equivalent or superior power output (Wattage).

There are 3 types of power supply in common use:
  • AT Power Supply - still in use in older PCs.
  • ATX Power Supply - commonly in use today.
  • ATX-2 Power Supply - recently new standard.
The voltages produced by AT/ATX/ATX-2 power supplies are:
  • +3.3 Volts DC (ATX/ATX-2)
  • +5 Volts DC (AT/ATX/ATX-2)
  • -5 Volts DC (AT/ATX/ATX-2)
  • +5 Volts DC Standby (ATX/ATX-2)
  • +12 Volts DC (AT/ATX/ATX-2)
  • -12 Volts DC (AT/ATX/ATX-2)
A power supply can be easily changed and are generally not expensive, so if one fails (which is far from uncommon) then replacement is usually the most economic solution.

ATX Power Supply Connectors Diagram



ATX Power Supply Pinouts Diagram



Making Really Good Homemade Printed Circuits Boards (PCBs)


Want to know how to make really really good homemade Printed circuit boards? This taken is from original posting of Mike's Electronic Stuff. This page contains a guide to producing consistently high quality PCBs quickly and efficiently, particularly for professional prototyping of production boards. Unlike most other PCB homebrew guides, emphasis is placed on quality, speed and repeatability rather than minimum materials cost, although the time saved by getting good PCBs every time usually saves money in the long run - even for the hobbyist, the cost of ruined PCB laminates can soon mount up!


With the methods described, you can produce repeatably good single and double-sided PCBs for through-hole and surface mount designs with track densities of 40-50 tracks per inch and 0.5mm SMD pitches.

This information has been condensed from over 20 years' experience of making PCBs, mostly as prototypes of boards to be put into production. If you follow the methods outlined here exactly, you WILL get excellent quality PCBs every time. By all means experiment, but remember that cutting corners can easily reduce quality & waste time.

I will only consider photographic methods in depth - other methods such as transfers, plotting on copper and the various 'iron-on' toner transfer systems are not really suited for fast, repeatable use. Although I've heard some good reports from some toner transfer systems, the problem with these is that the 'expensive part' is the film, and you can't really feed much less than an A5 sheet through a laser printer, so you waste a lot on small PCBs. With photoresist laminate and cheap transparency media, you only use as much of the expensive part (the board) as you need, and offcuts can usually be used later for smaller boards. Double-sided PCBs are also rather tricky with toner-transfer methods.

Source: Mike's Electric Stuff

Mosquito Repellant Circuit with BC547


This Moosquito repellat circuit uses two BC547 transnistor as astable multibibrator. The Astable Multivibrator, which is generally used as a signal generator, is once again used here to generate the desired frequencies. It is an excellent example of the fact, how versatile simple basic electronic circuit can be.



Astable Multivibrator Circuit Operation
When T1 is conducting T2 is off and when T2 is conducting, T1 is off. The capacitors C1 and C2 contributes decisively to this ON/OFF cycles for the transistors T1 and T2. The time taken by C1 and C2 to charge and discharge decides the shapeof the output waveform. Another important factor in the operation of the circuit is the fact that the transistor goes into conduction only when the base-emitter voltage exceeds 0.7 volts (for silicon transistors). From this basic knowledge we can visualise how the transistors exchange their roles and how the voltage on the collector of each transistor jumbs between the lower and upper level, producing a rectangular waveform. If you take a close look atcircuit, you will notice that C1 and C2 are not equal. They differ in their values by a factor of four.

The output signal will thus be a non symmetrical waveform. Such a non symmetrical signal contains more high frequency harminics compered to the normal square wave signal. The output of our circuit will have the basic frequency of 5 KHz along with harminics of 10, 15 and 20 KHz. If some insects are deaf to frequencies upto 5 KHz, they may react to 10 KHz or 15 KHz or even 20 KHz, one never knows ...

The piezo buzzer used should not have an internal oscillator built into it. The circuit consumes 0.3 ma current, and can give about 1500 hours of nonstop operation.

Parts List:
R1,R4 - 10 K Ohm
R2,R3 - 560 K Ohm
C1 - 82 PF
C2 - 330 PF
T1,T2 - BC547
Piezo Buzzer (Without internal oscillator)


Source: http://www.flashwebhost.com/circuit/mosquito.php

Battery Low Voltage Beeper


This electronic circuit is an alarm circuit for low battery condition. It provides an audible and visual low voltage warning for 12V battery powered devices. When the battery voltage is above the set point (typically 11V), the circuit is idle. If the battery voltage should fall below the set point, the LED will light and the speaker will emit a periodic beeping sound to warn of the impending loss of power. The circuit was designed for monitoring solar systems, but it could also be useful for automotive and other 12V applications.





Parts Lists : Printed Circuit Image (PostScript File) Component Placement Silkscreen (PostScript File)

How it works
U2 provides a 5V regulated voltage reference. U1 is wired as a comparator, it compares the fixed 5V regulated voltage to the voltage on the wiper of VR1, that is proportional to the 12V supply. When the supply drops below the set point, the output of U1 goes low, turning on Q1 and powering the beeper and the LED.

The beeper consists of U4, a tone generator, and U3, a low duty cycle pulse generator. The tone can be changed by adjusting R7, the beep rate can be changed by adjusting R5. A small amount of hysteresis is provided by R1 and the current through LED1 and the beeper, this separates the on and off points for thecircuit.

U2 provides a 5V regulated voltage reference. U1 is wired as a comparator, it compares the fixed 5V regulated voltage to the voltage on the wiper of VR1, that is proportional to the 12V supply. When the supply drops below the set point, the output of U1 goes low, turning on Q1 and powering the beeper and the LED.

The beeper consists of U4, a tone generator, and U3, a low duty cycle pulse generator. The tone can be changed by adjusting R7, the beep rate can be changed by adjusting R5. A small amount of hysteresis is provided by R1 and the current through LED1 and the beeper, this separates the on and off points for thecircuit.

Use of Battery Low Voltage Beeper
Connect the circuit to the 12V source that you wish to monitor. Turn S1 on, if the battery voltage is above the set point, nothing should happen.

As the battery voltage drops below the set point, the LED will light and a periodic beeping will come from the speaker. If the beeping becomes annoying, turn off S1. Be sure to chargethe battery soon, excessive discharging will shorten the life of most rechargeable batteries.

More about Battery Low Voltage Beeper

RF Dual DC Motors Controller

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The transmitter circuit consists of WZ-X01 RF module, Holtek HT-640 encoder and 8 bit A/D converter. U1 ADC0804 converts the analog voltage to digital data, U2 encodes that data (D0~D6) along with D6, D7 and transmitting through the RFtransmitter module.



The potentiometer VR1 varies the voltage to the A/D U1 pin6, since only the lower 6 bits are used; the trim pot VR2 has to adjust so that the maximum input to the U1 will not exceed 1.25V. The S2 (D6) and S3 (D7) are used for controlling the rotation direction of the motors. S1 set thetransmitter address; this address has to match with the address of the decoder circuit.





The receiver module WZ-R01 receives the data from the transmitter and feeds that data to the decoder U1 (HT-648L); the 8bit data will then be decoded. The first two significant bits D7 and D6 control the motor rotation direction. The lower 6 bits vary the duty cycle of the output pulse. U2 is a 12bit counter; it is configured so that it will reset itself every 64 counts. The oscillationcircuit forms by U4c, U4d and U4e providing approximately 1MHz clock to the counter U2.



The 8-bit magnitude comparator U3 (74HCT688) compares the data from the counter U2 with the data of the decoder U1; when data from both are match, it will output a pulse to cause the D-flip flop U5 changing it's state.



By varying the data output of the decoder from 0-64; the duty cycle of the output pulse at U5 pin5 can also change from 0-100%. This output pulse will then be used to control the speed of the motor.



With 1MHz clock input the PWM frequency output is about 15.6KHz. The motor has less audible noise when run at a frequency higher than 10KHz.You may need to change the frequency depending on the motor you're going to use.





The motor driver section is very straightforward; the LMD18200 can handle 3A continuous motor current and 6A peak. In this circuit the sign/magnitude mode of operation is implemented. The current sensing circuit provides protection to both the driver and the motor; it set at 2A max. You can change the current limit by using a different current sensing resistor value (see LMD18200 data sheet for details) or the voltage reference at pin6 of the U7Op-Amp



All of the components use in this project can be purchased from us. Email us at wzmicro@worldnet.att.net, if you have any questions or comments. Your feedback is mostly appreciated.

Stereo Parabolic Microphone

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This circuit is a stereo amplifier for a high sensitivity stereo parabolic microphone that able to used for listening to distant sounds. Typical parabolic microphones are monophonic, this unit has a stereo audio path that helps produce more realistic sounding audio. The Big-E can be used with headphones or as an audio source for a stereo tape recorder or a PC sound card.




This circuit also works nicely as a remote stereo audio receiver for accompanying a video surveillance system. It is capable of operating on the end of a four wire shielded cable that is more than 100 feet long. For remote operation, a set of inexpensive amplified PC speakers can be connected to the outputs for monitoring thesound.

Specifications
Operating Voltage: 9-15V (9V Nominal) DC
Operating Current: 7ma at 9V DC

How Does It Work
The circuit consists of two identical audio channels and some basic power supply filtering components. Only the left channel will be described.



The mini condenser microphone converts sounds into an electrical signal. Resistor R1 provides bias for the condensor microphone's internal amplifier transistor. The 2N3906 PNP transistor acts as a low noise microphone input amplifier. The 10K gain potentiometer is used for adjusting the audio signal level. A stereo 10K audio taper pot can be used for adjusting both channels simultaneously, or individual 10K trimmers can be used for fixed gain applications. The preamp output signal is fed into the 1458 op-amp, which boosts the audio to a level that is sufficient for driving an 8-ohm headphone or a tape recorder input. The 1458 amplifier stage is fixed gain (10X) in the inverting configuration, it drives the headphone speakers.

Capacitor C9 provides DC isolation from the 1458 op-amp output, which sits at half of the supply voltage. Resistor R13 provides impedance protectionfor the op-amp output and reduces audio distortion when driving low impedance headphones.

DC bias for the 1458 op-amps is set at half of the supply voltage by the R16/R17 voltage divider. Capacitors C13 and C14 filter the DC power supply for the op-amp stage. The DC is further filtered for the input preamp transistors through resistor R15 and capacitor C11. Diode D1 and resistor R18 protect the circuit from reverse battery polarity.

Construction
The Big-E circuit can be assembled on a circuit board, or hand wired. The board should be installed in a metal box for shielding from unwanted hum. For surveillance applications, the condenser microphones can be mounted directly on the PC board or on the edge of the metal box. The volume control can be mounted on the edge of the box, two 3.5MM mono jacks were usedfor the microphone inputs, a 3.5MM stereo jack was used for the headphone output. The 9V battery was mounted inside of the box, power is switched via a switch on the 10K stereo potentiometer.

The parabolic microphone assembly was made from an old Chinese wok cooker lid. The microphones are mounted on a metal standoff that places them at the focal point of the parabolic reflector. Pre-formed computer microphones were used for the model shown. The optimal microphone position can be found by pointing the reflector at a distant audio source, then moving the microphonesfor the loudest sound. The circuit box was mounted on the back side of the wok lid, it was attached to a piec of 1/2" square aluminum tubing, which forms a handle.

Parabolic Microphone Use
Start with the volume turned down, point the Big-E at a remote sound source, then gradually turn the volume up until the sound is heard. Be careful not to hit the side of the parabolic dish when listening, loud sounds can result. Also, beware that a malicious friend can cause you pain in the ears by talking loudly at the parabolic mic. It is advisable to wear the headphones partially off of your ears while you get used to the operation of the device. The Big-E is great for listening to birds and distant thunderstorms. It is also possible to hear the rustling of leaves on the top of a distant tree during a breezy day. Close-in wind noise may overpower distant sounds.

Stereo Parabolic Microphone PCB
Printed Circuit Image
Component Placement Silkscreen

Source: The Big-E Stereo Parabolic Microphone

12V Inverter Circuit

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This 12V inverter is very easy to build, cheap components that many electronics hobbyists may even already have. Though it is possible to build a more powerful circuit, the complexity caused by the very heavy currents to be handled on the low-voltage side leads to circuits.


The circuit diagram of 12v inverter is easy to follow. A classic 555 timer chip, identified as IC1, is configured as an astable multivibrator at a frequency close to 100 Hz, which can be adjusted accurately by means of potentiometer P1. It is used to drive a D type flip-flop produced using a CMOS type 4013 IC. This produces perfect complementary squarewave signals (in antiphase) on its Q and Q outputs suitable for driving
the output power transistors.



As the output current available from the CMOS 4013 is very small, Darlington power transistors are used to arrive at the necessary output current. We have chosen MJ3001s from the now defunct Motorola (only as a semi-conductor manufacturer, of course!) which are cheap and readily available, but any equivalent powerDarlington could be used.

These drive a 230 V to 2 × 9 V centre tapped transformer used ‘backwards’ to produce the 230 V output. The presence of the 230 VAC voltage is indicated by a neon light, while a VDR (voltage dependent resistor) type S10K250 or S07K250 clips off the spikes and surges that may appear at the transistor switching points.

12 Inverter Parts List
Resistors
R1 = 18kΩ
R2 = 3kΩ3
R3 = 1kΩ
R4,R5 = 1kΩ5
R6 = VDR S10K250 (or S07K250)
P1 = 100 kΩ potentiometer
Capacitors
C1 = 330nF
C2 = 1000 μF 25V
Semiconductor
T1,T2 = MJ3001
IC1 = 555
IC2 = 4013
Miscellaneous
LA1 = neon light 230 V
F1 = fuse, 5A
TR1 = mains transformer, 2x9V 40VA (see text)
4 solder pins
PCB,

The Darlington transistors should be fitted onto a finned anodized aluminium heat-sink using the standard insulating accessories of mica washers and shouldered washers, as their collectors are connected to the metal cans and would otherwise be short-circuited.

An output power of 30 VA implies a current consumption of the order of 3 A from the 12 V battery at the ‘primary side’. So the wires connecting the collectors of the MJ3001s [1] T1 and T2 to the transformer primary, the emitters of T1 and T2 to the battery negative terminal, and the battery positive terminal to the transformer primary will need to have a minimum crosssectional area of 2 mm2 so as to minimize
voltage drop. The transformer can be any 230 V to 2 × 9 V type, with an E/I iron core or toroidal, rated at around 40 VA.



Properly constructed on the board shown here, the 12 inverter circuit should work at once, the only adjustment being to set the output to a frequency of 50 Hz with P1.

The circuit should not be too difficult to adapt to other mains voltages or frequencies, for example 110 V, 115 V or 127 V, 60 Hz. The AC voltage requires a transformer with a different primary voltage (which here becomes the secondary), and the frequency, some adjusting of P1 and possibly minor changes to the values of timing components R1 and C1 on the 555. Author: B. Broussas

Telephone Hybrid Circuit This electronic circuit is a telephone hybrid. It is intended to be used to create an easy connection beetween telephone lin

Telephone Hybrid Circuit

This electronic circuit is a telephone hybrid. It is intended to be used to create an easy connection beetween telephone line and studio equipment. Connect the two wires of the telephone line to the tip and ground of the line input and connect the telephone itself to the phone output on the tip and ground only.


Now the hybrid is interfaced (fully balanced) between your telephone and its connection to the outside world. The hybrid is now capable of splitting the send and return signals.Connect the hybrid balanced audio input to a (preferabie) balanced output of around +4dBu. This output has to be the mix of all signals except the signal coming from the hybrid itself to avoid feedback. An Aux. output will do, or in broadcast mixers a modified cleanfeed is the best.


12V Inverter Circuit

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This 12V inverter is very easy to build, cheap components that many electronics hobbyists may even already have. Though it is possible to build a more powerful circuit, the complexity caused by the very heavy currents to be handled on the low-voltage side leads to circuits.


The circuit diagram of 12v inverter is easy to follow. A classic 555 timer chip, identified as IC1, is configured as an astable multivibrator at a frequency close to 100 Hz, which can be adjusted accurately by means of potentiometer P1. It is used to drive a D type flip-flop produced using a CMOS type 4013 IC. This produces perfect complementary squarewave signals (in antiphase) on its Q and Q outputs suitable for driving
the output power transistors.



As the output current available from the CMOS 4013 is very small, Darlington power transistors are used to arrive at the necessary output current. We have chosen MJ3001s from the now defunct Motorola (only as a semi-conductor manufacturer, of course!) which are cheap and readily available, but any equivalent powerDarlington could be used.

These drive a 230 V to 2 × 9 V centre tapped transformer used ‘backwards’ to produce the 230 V output. The presence of the 230 VAC voltage is indicated by a neon light, while a VDR (voltage dependent resistor) type S10K250 or S07K250 clips off the spikes and surges that may appear at the transistor switching points.

12 Inverter Parts List
Resistors
R1 = 18kΩ
R2 = 3kΩ3
R3 = 1kΩ
R4,R5 = 1kΩ5
R6 = VDR S10K250 (or S07K250)
P1 = 100 kΩ potentiometer
Capacitors
C1 = 330nF
C2 = 1000 μF 25V
Semiconductor
T1,T2 = MJ3001
IC1 = 555
IC2 = 4013
Miscellaneous
LA1 = neon light 230 V
F1 = fuse, 5A
TR1 = mains transformer, 2x9V 40VA (see text)
4 solder pins
PCB,

The Darlington transistors should be fitted onto a finned anodized aluminium heat-sink using the standard insulating accessories of mica washers and shouldered washers, as their collectors are connected to the metal cans and would otherwise be short-circuited.

An output power of 30 VA implies a current consumption of the order of 3 A from the 12 V battery at the ‘primary side’. So the wires connecting the collectors of the MJ3001s [1] T1 and T2 to the transformer primary, the emitters of T1 and T2 to the battery negative terminal, and the battery positive terminal to the transformer primary will need to have a minimum crosssectional area of 2 mm2 so as to minimize
voltage drop. The transformer can be any 230 V to 2 × 9 V type, with an E/I iron core or toroidal, rated at around 40 VA.



Properly constructed on the board shown here, the 12 inverter circuit should work at once, the only adjustment being to set the output to a frequency of 50 Hz with P1.

The circuit should not be too difficult to adapt to other mains voltages or frequencies, for example 110 V, 115 V or 127 V, 60 Hz. The AC voltage requires a transformer with a different primary voltage (which here becomes the secondary), and the frequency, some adjusting of P1 and possibly minor changes to the values of timing components R1 and C1 on the 555. Author: B. Broussas

Power Supply Circuit 12-15 Volt 20A [Power Supply 12V 20A MJ2955 Mountage] Output voltage of the power supply circuit is adjustable from fine potensi


Output voltage of the power supply circuit is adjustable from fine potensiometer from 12V to 15v. It is suitable for all 12V power supply devices, or devices which are normally connected to a 12V battery or a vehicle with a 12V power supply system. This tension is usually 13.8 V.




For above reason, The Power Supply is also set to this tension, all right, however, any voltage from 12V to 14V. In this case, the tension is set somewhere around 13.6 V. To provide tension resistance in addition to voltage regulator 78S12. Instead potentiometer 100R inserted resistor 56R.





The scheme of the power supply is simple, but it is partly taken from some of the schemes taken up in the past. The material used is easily obtainable in electronic component shops, and this was the condition when I started to design this power supply.


More about Power Supply Circuit

AM FM Simultaneous Transmitter Using Digital IC

AM FM Simultaneous Transmitter Using Digital IC

UNIPOLAR Stepper Motor Driver (74194) UNIPOLAR Stepper Motor Driver (74194) This page features simple and inexpensive, stand alone UNIPOLAR stepper m

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UNIPOLAR

Stepper Motor Driver (74194)

This page features simple and inexpensive, stand alone UNIPOLAR stepper motor driver using parts that are available from many sources.

The driver is designed for medium and low speed applications with motors that draw up to 1.0 amperes per phase.

This driver provides only basic control functions such as: Forward, Reverse, Stop and has a calculated Step rate adjustment range of 0.72 (1.39 sec) to 145 steps per second. (Slower and faster step rates are also possible. - See notes.)

The only step angle for this driver is the design step angle of the motor itself. 'Half-stepping' is not possible.

A 74194 - Bidirectional Universal Shift Register from the 74LS or 74HC - TTL families of logic devices to produce the stepping pattern.

The stepper motor driver on this page replaces the Unipolar Stepper Motor Driver (74194) 2007 That was previously available through this web site.

A printed circuit board is available for this circuit.


Stepper Motor Driver PCB Circuit

The following schematic is for the printed circuitboard version of the 2008 stepper motor driver.

Basic Controls For The Stepper Driver

The direction is selected by an ON-OFF-ON toggle switch.

The stepping rate is shown being set by a 1 Megohm potentiometer (RT). Using the component values shown for R1, RT, R2 and C1, the calculated step rate range is between 0.72 steps per second (1.39 seconds) to 145 steps per second.


Basic Stepper Motor Driver Operation

  1. The LM555 (IC 1) astable oscillator produces CLOCK pulses that are fed to PIN 11 of the 74194 (IC 2) shift register.
  2. Each time the output of the LM555 timer goes HIGH (positive) the HIGH state at the 74194's OUTPUT terminals, (PIN's 12, 13, 14, 15), is shifted either UP or DOWN by one place.

    The direction of the output shifting is controlled by switch S1. When S1 is in the OFF position (centre) the HIGH output state will remain at its last position and the motor will be stopped.

    Switch S1 controls the direction indirectly through transistors Q2 and Q3.

    When the base of Q2 is LOW the output shifting of IC 2 will be pins 15 - 14 - 13 - 12 - 15; .etc.

    When the base of Q3 is LOW the output shifting of IC 2 will be pins 12 - 13 - 14 - 15 - 12; .etc.

    The direction of the output's shifting determines the direction of the motor's rotation.

  3. The outputs of the 74194 are fed to four sets of paralleled segments of a ULN2803 Darlington driver (IC 3).

    When an input of a ULN2803 segment is HIGH, its darlington transistor will turn ON and that OUTPUT will conduct current through one of the motors coils.

  4. As the coils of the motor are turned ON in sequence the motor's armature rotates to follow these changes. Refer to following diagram.


Inputs Vs. Outputs Waveforms

The following diagram shows the stepping order for the outputs of the ULN2803 (IC 3) as compared to the input and output of the 74194 (IC 2). The output is shown stepping in one direction only.


Integrated Circuit Chips Used

  • IC 1 - LM555 - Timer, normally configured as an astable oscillator but can be used a monostable timer for 1 step at a time operation or can be used as a buffer between external inputs and IC2. (See later Diagrams.)

  • IC 2 - 74194 - 4-Bit Bidirectional Universal Shift Register. The shift register provides the logic that controls the direction of the drivers output steps.

    This circuit can use either the 74LS194 or the 74HC194 shift register IC. Their logic functions are identical but the 74HC194 IC is a CMOS type that can be damaged by static electricity discharges. Antistatic precautions should be used when handling the 74HC194 to avoid damage.

    If you are purchasing your own parts use the 74LS194 IC if it is available.

  • IC 3 - ULN2803 - 8 Segment, Darlington, High Current, High Voltage Peripheral Driver. Each segment can handle currents of up to 500 milliamps and voltages up to 50 volts. In this circuit 2 output segments are connected in parallel, this allows a maximum output current of 1 amp per phase.

  • IC 4 - LM7805 - Positive 5 Volt Regulator. Provides low voltage power to the driving circuitry and can also power external control circuits.

It is not the purpose of this page to provide full explanations of how these devices work. Detailed explanations can be found through datatsheets that are available from many source on the internet.


74194 Stepper Motor Driver Notes

  • Due to the lack of error detection and limited step power, this circuit should not be used for applications that require accurate positioning. (The driver is designed for hobby and learning uses.)

  • There are links to other stepper motor related web pages further down the page. These may be helpful in understanding stepper motor operation and control.

  • For the parts values shown on the schematic, if the external potentiometer (RT) is set to "ZERO" ohms, the calculated CLOCK frequency will be approximately 145 Hz and a motor will make 145 steps per second. This step rate should be slow enough for most motors to operate properly.

    The maximum RPM at which stepper motors will operate properly is low when compared to other motor types and the torque the motor produces drops rapidly as its speed increases. Testing may be needed to determine the minimum values for RT and C1 to produce the maximum CLOCK frequency for any given motor. Data sheets, if available, will also help determine this frequency.

  • If RT is set to 1 Megohm, the calculated step rate will be 0.73 Hz and the motor would make 1 step every 1.39 seconds.

    There is no minimum step speed at which stepper motors cannot operate. Therefore, in theory, the values for RT and C1 can be as large as desired but there are practical limitations to these values. The main limitation is the 'leakage' current of electrolytic capacitors.

  • External CLOCK pulses can also be used to control the driver by passing them through IC 1 via the "T2" terminal of the circuitboard. Using IC 1 as an input buffer should eliminate "noise" that could cause the 74194's output to go into a state where more than one output is HIGH.

  • If stepping rates greater than 145 per second are needed, capacitor C1 can be replaced with one of lower value.

    A 0.47uF capacitor would give a calculated range of 1.5 to 310 steps per second.

    A 0.33uF capacitor would give a calculated range of 2.2 to 441 steps per second.

    Alternately, capacitor C1 can be removed from the circuitboard and an external clock source connected at terminal 'T2'. With C1 removed, the practical limit on the step rate is the motor itself.

  • In the above items the "calculated" minimum and maximum CLOCK frequencies are valid for the nominal part values shown. Given the tolerances of actual components and the leakage currents of electrolytic capacitors the actual CLOCK rates may be lower or higher.

  • The direction of the motor can be controlled by another circuit or the parallel output port of a PC. This will work as long as the voltage at the bases of Q2 and Q3 can be made lower than 0.7 volts. Additional NPN transistors may be required to achieve this result, depending on the method used.

  • If the bases of both Q2 and Q3 are made LOW at the same time the SN74194 will go into a RESET mode. This will cause the step sequence to stop and on the next clock pulse pins 15 and 14 will go to a HIGH state.

    Making the bases of both Q2 and Q3 LOW at the same time can be used to reset the SN74194 to its starting position without having to remove the circuit power.

  • Each stepper motor will have its own power requirements and as there is a great variety of motors available. This page cannot give information in this area. Users of this circuit will have to determine motor phasing and power requirements for themselves.

    Power for the motors can be regulated or filtered and may range from 12 to 24 volts with currents up to 1,000 milliamps depending on the particular motor.

    Motors that operate at voltages lower than 12 volts can also be used with this driver but a separate supply of of 9 to 12 volts will be needed for the control portion of the circuit in addition to the low voltage supply for the motor.

  • A LED connected to the output of the LM555 timer (IC 1) flashes at the CLOCK frequency. If a direction has been selected, The motor will move one step every time the led turns ON.

  • There is no CLOCK output terminal on the circuitboard but there is a pad to the right of the LED that can be used if a clock output signal is required. This pad is connected to pin 3 of the LM555 IC.

  • The LM7805, positive 5 volt regulator used on the circuitboard can also be used to provide power for external control circuits. With its tab trimmed off, the regulator can easily dissipate up to 1 watt.

    For a 12 volt supply, external circuits can draw up to 100 milliamps.

    For a 24 volt supply, external circuits can draw up to 25 milliamps.

  • The photo of the circuitboard shows the tab of the 7805 regulator cut off, this is an option that is available on request.


74194 Stepper Driver Initialization Notes

  • When power is applied to the 74194 Stepper Driver circuit there is a very short delay before stepping of the outputs can begin. The delay is controlled by Capacitor C2, resistor R4 and transistor Q1.

  • The function of the delay is to allow the outputs of IC 2 to be set with pin 12 in a HIGH state and pins 13, 14 and 15 in a LOW state before direction control becomes active. The delay also prevents IC 1 from oscillating until IC 2 has been set.

  • If the power to the circuit is turned off, there should be a pause of at least 10 seconds before it is reapplied. The pause is to allow capacitor C2 to discharge through R4 and D2.

  • If the initialization delay were not used, IC 3 could have: none, any or all of its outputs in a high state when stepping is started. This would cause the motor to move incorrectly or not at all during normal operation.

The 2008 version of the stepper motor driver is ready to start operation as soon as the the initialization delay is complete.


Stepper Circuit Board Parts List

Qty.
Part #
DigiKey Part #
DigiKey Description
1 - IC 1 - LM555CNFS-ND - IC TIMER SINGLE 0-70DEG C 8-DIP
1 - IC 2* - 296-9183-5-ND - IC BI-DIR SHIFT REGISTER 16-DIP
1 - IC 3 - 497-2356-5-ND - IC ARRAY EIGHT DARLINGTON 18 DIP
1 - IC 4 - LM7805ACT-ND - IC REG POS 1A 5V +/-2% TOL TO-220

-
-
-
3 - Q1, 2, 3 - 2N3904FS-ND - IC TRANS NPN SS GP 200MA TO-92
1 - D1 - 160-1712-ND - LED 3MM GREEN DIFFUSED
1 - D2 - 1N4148FS-ND - DIODE SGL JUNC 100V 4.0NS DO-35
1 - D3 - 1N4001FSCT-ND - DIODE GEN PURPOSE 50V 1A DO41

-
-
-
4 - R1, 2, 8, 9 - 3.3KQBK-ND - RES 3.3K OHM 1/4W 5% CARBON FILM
3 - R4, 6, 7 - 10KQBK-ND - RES 10K OHM 1/4W 5% CARBON FILM
1 - R3, 5 - 470QBK-ND - RES 470 OHM 1/4W 5% CARBON FILM

-
-
-
1 - C1 - P5174-ND - CAP 1.0UF 50V ALUM LYTIC RADIAL
2 - C2, 3 - P5177-ND - CAP 4.7UF 50V ALUM LYTIC RADIAL
1 - C4 - P5168-ND - CAP 470UF 35V ALUM LYTIC RADIAL

-
-
-
4 -
- ED1602-ND - TERMINAL BLOCK 5MM VERT 3POS







* - The DigiKey part number for IC 2 is for the 74HC194 - CMOS IC. This IC is a CMOS type that can be damaged by static electricity discharge.

DigiKey does not carry the 74LS194 in small quantities. It is available for other sources such as Mouser Electronics - stock number 47053 and Jameco Electronics - stock number 59574LS194AN as well as many other sources. Be sure that the IC's have the DIP package.

* - The Part Number for Q1, Q2 and Q3 is for 2N3904s. Almost any NPN, Switching or Small signal type will work, the 2N4400 is one example.




Circuitboards And Parts

The following picture is of an assembled circuitboard for the Unipolar Stepper Motor Driver. The board measures 2 inches by 3 inches and has been commercially made. The board is not tinned or silkscreened.

The relative positions of the terminal blocks at the sides and ends of the circuitboard correspond with those in the schematic diagram and the control circuit examples.

The photo of the circuitboard shows the tab of the 7805 regulator cut off, this is an option that is available on request.

The price for 1 circuitboard is 9.50 dollars US plus postage.

The price for 1 kit of parts and a circuit board is 19.00 dollars US plus postage.

The price for 1 Assembled circuitboard is 22.00 dollars US plus postage.

If you are interested in a circuitboard and parts for this circuit please send an email to the following address: rpaisley4@cogeco.ca

Please Read Before Ordering

Due to delays in acquiring 74LS194 type ICs, the assembled circuitboards and kits will use the 74HC194 - CMOS type IC. The 74HC194 will be mounted in a socket to eliminate soldering this device during assembly.

Although the 74HC194 is sensitive to damage from static discharge, once it is installed in its socket the IC is very safe as all of its pins are connected to the 5 volt supply or to common through low impedance paths.

When handling the board, avoid nonconductive surfaces such as plastics or glass. If the circuit board is to be placed in a plastic case, do the assembly work on a wood or metal surface that is connected to earth. Also avoid carpeted areas during assembly.

A good practice is to touch the work surface before touching the circuitboard.


PCB Parts Placement Diagram




Other Information And Diagrams


Wiring for longer distances.

If the motor is some distance from the circuit board or power supply, it might be best to separate the motor's power supply lead from the circuit board's supply as illustrated in the next diagram. The motor could be connected using larger gauge wire.

This will keep most effects of the motors current pulses away from the supply to the circuit board. A filter capacitor could be placed in the motor's supply circuit as well.


Connecting A 6 Lead Motor to the Stepper Driver

It may be necessary to move the coil leads around to get the motor to turn properly. Leave one wire connected permanently and change the other three coil leads as needed.


Single-Step Input

The connections in the following diagram will allow the motor to make single steps. A toggle switch could be used to select between single and continuous steps if the 1 Megohm potentiometer was included in the circuit.


External Controls Using Transistors


External Controls Using Optoisolators

The use of optoisolators provides complete isolation between the driver and the external control circuit.


Automated Motor Control Circuit - (Voltage Comparators)

The circuit above replaces the direction control switch with a "window" type voltage comparator circuit. Potentiometer "R IN" could be a temperature or light sensing circuit.

  • When the voltage at the centre tap of R IN is between the HIGH and LOW voltages set by resistors R1, R2, and R3 the motor will be stopped.

  • When the voltage at the centre tap of R IN is above the HIGH voltage between R1 and R2 the motor will be step in the FWD direction.

  • When the voltage at the centre tap of R IN is below the LOW voltage between R2 and R3 the motor will be step in the REV direction.

In a practical application the direction of the motors load, a heating duct damper for example, would bring the temperature represented by the voltage at R IN back to the range between the HIGH and LOW voltage setpoints.

The limit switches at the outputs of the comparators are used to prevent the damper from going beyond its minimum and maximum positions by to stopping the motor.

Also see Voltage Comparator Information And Circuits - Voltage Window Detector Circuit.


Slower Step Rates

Additional capacitance can be added to the IC 1 circuit to provide slower motor step rates. There is a limit to this approach as control of the step rate becomes less accurate as the capacitance increases and at some point the timer will stop working due to the leakage currents of the capacitors.


Fast External Clock

An external clock with a step rate greater than 145 steps per second can be connected to the driver circuit by removing capacitor C1. There is no limit on how slow the clock input can be.


Using Low Voltage Motors

Stepper motors that require less than 12 volts can be controlled by the driver by removing diode D3 from the circuitboard and connecting a external power supply to the control section of the driver.

Also, IC 4 could be removed from the circuitboard and a regulated 5 volt supply connected at the '+5V' terminal.


Single Input Direction Control

The following circuits allow the direction of the motor to be controlled by as single, ON-OFF input. The maximum input voltage is 5 Volts.


Using Higher Current Motors

The next circuit uses TIP125 Darlington type transistors to increase the current capacity of the 74194 driver circuit to 5 amps per winding.

Depending on the current required for the motor, small heatsinks may be needed for the transistors.



Other Information

Animated operation of stepper motors.

http://de.nanotec.com/schrittmotor_animation.html

For the motor driver circuit on this web page, only 1 coil is ON at a time so the rotor of the motor would be aligned with one of the stator's poles and not half way between poles as shown in the animation.


The following links are for stepper motor related pages that have information on other types of driver circuits and motors.

www.cs.uiowa.edu/~jones/step/circuits.html

www.doc.ic.ac.uk/~ih/doc/stepper/control2/connect.html




Please Read Before Using These Circuit Ideas

The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.

If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.

Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.


Thursday, 12 March 2009 Wireless RF PWM dual motor controller The transmitter circuit consists of WZ-X01 RF module, Holtek HT-640 encoder and 8-bit A

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Thursday, 12 March 2009

Wireless RF PWM dual motor controller

The transmitter circuit consists of WZ-X01 RF module, Holtek HT-640 encoder and 8-bit A/D converter. U1 ADC0804 converts the analog voltage to digital data; U2 encodes that data (D0~D6) along with D6, D7 and transmitting through the RF transmitter module. The potentiometer VR1 varies the voltage to the A/D U1 pin6, since only the lower 6 bits are used; the trim pot VR2 has to adjust so that the maximum input to the U1 will not exceed 1.25V. The S2 (D6) and S3 (D7) are used for controlling the rotation direction of the motors. S1 set the transmitter address; this address has to match with the address of the decoder circuit.


The receiver module WZ-R01 receives the data from the transmitter and feeds that data to the decoder U1 (HT-648L); the 8bit data will then be decoded. The first two significant bits D7 and D6 control the motor rotation direction. The lower 6 bits vary the duty cycle of the output pulse. U2 is a 12bit counter; it is configured so that it will reset itself every 64 counts. The oscillation circuit forms by U4c, U4d and U4e providing approximately 1MHz clock to the counter U2.

The 8-bit magnitude comparator U3 (74HCT688) compares the data from the counter U2 with the data of the decoder U1; when data from both are match, it will output a pulse to cause the D-flip flop U5 changing it's state.

By varying the data output of the decoder from 0-64, the duty cycle of the output pulse at U5 pin5 can also change from 0-100%. This output pulse will then be used to control the speed of the motor.

With 1MHz clock input the PWM frequency output is about 15.6KHz. The motor has less audible noise when run at a frequency higher than 10KHz.You may need to change the frequency depending on the motor you're going to use.

The motor driver section is very straightforward; the LMD18200 can handle 3A continuous motor current and 6A peak. In this circuit the sign/magnitude mode of operation is implemented. The current sensing circuit provides protection to both the driver and the motor; it set at 2A max. You can change the current limit by using a different current sensing resistor value (see LMD18200 data sheet for details) or the voltage reference at pin6 of the U7Op-Amp

The above picture is the prototype, It works great! We had been able to control the motors at more than 100 feet away.

You may download this whole page in MS word format.

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