Secret Diagram: control

Showing posts with label control. Show all posts

Thursday, 23 March 2017

AC Power Control with Thyristor Phase Angle Control using triac with PIC16F877A

Principle of Phase Angle Control

Top - Output Voltage

Bottom - Gate Drive Signal

Image source: Wikipedia (http://en.wikipedia.org/wiki/File:Regulated_rectifier.gif)

The photo above clearly illustrates phase angle control: output voltage controlled by the gate drive signal applied to a thyristor. What is phase angle control? That is what I'm going to talk about in this article.

Phase angle control is a method of PWM applied to AC input voltages, usually the mains supply. Of course, the AC supply could be from a transformer or any other AC source, but the mains supply is the most common input – this gives the phase angle control method its greatest usefulness. It has of course become quite obvious from the title (and I’m sure most of you reading will already know this) that the purpose of phase angle control is to control or limit power to the load.

The power device used in phase angle controllers is a thyristor – mostly triacs or SCRs. (There are methods of phase controlling employing high frequency switching using a MOSFET or IGBT, but here I’ll talk about phase angle control with thyristors only). The power flow to the load is controlled by delaying the firing angle (firing time each half-cycle) to the power device.

We know that the thyristor is a latching device – when the thyristor is turned on by a gating signal and the current is higher than the holding current and the latching current, the thyristor stays on, until the current through it becomes sufficiently low (very close to zero). The thyristor turns off when current through it becomes zero, as happens at the AC mains zero crossing. This is the natural line commutation. (Another method of turning the thyristor off is by forced commutation. I won’t go into that now.) The assumption here is that the load is resistive and has little to no inductance. Of course, this is not always the case, as inductive loads are often used. However, I’ll work with this assumption for now.

Now, with that covered, you should read this article first before proceeding to the rest of this article:

Zero crossing detection with PIC16F877A: http://www.blogspot.com/2016/10/zero-crossing-detection-with-pic16f877a.html

I’ve added the circuit, code and simulation of an example later in this article. And that uses a triac as the power device. So, from now on, I’ll just refer to the triac instead of talking about a thyristor in general.

So, in phase angle control, a gate pulse is sent to the triac. This is sent at a time between one zero crossing and the next. Without the gate pulse sent to the triac, right after zero-crossing, the triac is off and no current flows through it. After a certain time, the gating signal is given to the triac and it turns on. The triac then stays on until the current through it becomes zero (natural line commutation). This is at the next zero crossing. For simplicity’s sake and as usually should be, assume that the current through the triac (when on) is larger than the latching current and the holding current. If you didn’t already know this, the latching current is the current that must pass through the triac right after it is turned on to ensure that it latches. The holding current is the current level through the triac below which the triac will turn off. So, the assumption that current through the triac is higher than the latching current and the holding current means that the triac stays on once it is fired on. It stays on until the current through it is zero.

This means that the voltage is supplied to the load for a fraction of the cycle, determined by how long the triac is on. How long the triac is on, is, in turn, determined by the delay time between the zero-crossing and the applying of the triac gating signal.

So, to sum it up, we adjust the voltage or power delivered to the load by delaying the trigger signal to the triac. One thing to remember is that, the delivered voltage and power are not linearly related to the firing phase angle.

There are two voltages here that we are concerned with – the RMS voltage and the average voltage. The RMS voltage governs the power output to resistive loads such as incandescent bulbs and resistive heaters. The average value relates to devices that function on the average voltage level. This is important because, when testing, your voltmeter will register the average voltage – and not the true RMS voltage – unless you have a “true RMS voltmeter”. Most inexpensive voltmeters are not true RMS meters but will respond to average value changes.

To clarify why power and voltage are not linearly related, let’s examine the formula relating the two.

So, assuming a constant resistance (be careful if you’re using incandescent lamps, since they are NOT constant resistance devices), power is directly proportional to the square of the voltage. So, if you half the voltage, the power is not halved, but is reduced to one-fourth the original power! One-fourth power with half the voltage!

Now let’s now go on to the design part – how we’re actually going to do this.

For the microcontroller, I’ve chosen the extremely popular PIC 16F877A. However, since this application requires only a few pins, you can easily use any other small microcontroller for this purpose, such as PIC 12F675.

The zero-crossing is done using the bridge-optocoupler method as I had previously shown. For details regarding the zero-crossing, please go through the article:

Zero crossing detection with PIC16F877A: http://www.blogspot.com/2016/10/zero-crossing-detection-with-pic16f877a.html

Now, let’s take a look at the code:

//---------------------------------------------------------------------------------------------------------

//Programmer: Syed Tahmid Mahbub

//Compiler: mikroC PRO for PIC v4.60

//Target PIC: PIC16F877A

//Program for phase angle control

//---------------------------------------------------------------------------------------------------------

unsigned char FlagReg;

sbit ZC at FlagReg.B0;

void interrupt(){

if (INTCON.INTF){ //INTF flag raised, so external interrupt occured

ZC = 1;

INTCON.INTF = 0;

}

void main() {

PORTB = 0;

TRISB = 0x01; //RB0 input for interrupt

PORTA = 0;

ADCON1 = 7; //Disable ADC

TRISA = 0xFF; //Make all PORTA inputs

PORTD = 0;

TRISD = 0; //PORTD all output

OPTION_REG.INTEDG = 0; //interrupt on falling edge

INTCON.INTF = 0; //clear interrupt flag

INTCON.INTE = 1; //enable external interrupt

INTCON.GIE = 1; //enable global interrupt

while (1){

if (ZC){ //zero crossing occurred

delay_ms(2);

PORTD.B0 = 1; //Send a pulse

delay_us(250);

PORTD.B0 = 0;

ZC = 0;

}

There isn’t much to it. The zero-crossing is first checked. After zero-crossing occurs, a small delay is present before the triac is fired. Here, I’ve used 2ms. So, the triac is fired 2ms after the zero-crossing occurs. The gating signal is removed 250µs after that. 250µs is enough time to ensure that the triac has turned on. Even though the gating signal is removed, the triac stays on until the next zero-crossing as it is a latching device. Now you may ask, why remove the gating signal? Just keep it on till the next zero-crossing. Well, that'd work too. The problem there would be that, there would be high switching losses of the thyristor. The gate drive resistance would dissipate immense amounts of power - all for no reason, since the triac would be on even if the signal was removed.

The rest of the code should be easy to understand and should be self-explanatory – I’ve added comments to help you understand.

Now let’s take a look at my circuit setup and then the output waveform using this code:

Fig. 1 - Circuit Diagram (Click on image to enlarge)

You should choose R1 depending on the gate current requirements of the triac. It must also have a sufficiently high power dissipation rating. Usually, the instantaneous power may be very high. But since current flows through the resistor for only 250us (1/40 of a 50Hz half cycle), the average power is small enough. Usually, 2W resistors should suffice.

Let’s assume we’re using a BT139-600 triac. The maximum required trigger current is 35mA. Although the typical trigger current is lower, we should consider the maximum required trigger current. This is 35mA for quadrants I, II and III. We will only be firing in quadrants I and III. So, that is ok for us – we need to consider 35mA current.

If you aren’t sure what quadrants are, here’s a short description. First take a look at this diagram:

Fig. 2 - Triac Triggering Quadrants

If you look back again at the diagram, you’ll see that we’re driving gate from MT2. So, we can say that, with respect to MT1, when MT2 is positive, so is the gate. With respect to MT1, when MT2 is negative, so is the gate. From the diagram above, you can see that these two cases are in quadrants I and III. This is what I meant when I mentioned that we’re driving only in quadrants I and III.

The driver in the circuit is the MOC3021. This is a random phase optically isolated triac output driver. When the LED is turned on, the triac in the MOC3021 turns on and drives the main triac in the circuit. It is a “random phase” driver meaning that it can be driven on at any time during the drive signal, as is required for phase angle control. There are other drivers that only allow drive at the zero-crossing. These cannot be used for phase angle control as phase angle control requires drive after zero-crossing. For guaranteeing that the triac is latched, the LED side of the MOC3021 must be driven with at least 15mA current. The maximum current rating for the LED is 60mA. The peak current rating for the triac is 1A. You should find that we have stayed within these limits in the design.

Here’s the output waveform:

Fig. 3 - Triac firing with 2 ms delay

Green: Input AC
Yellow: AC Output after phase angle control
Pink: Gate Drive signal

You can clearly see that before the gate driving signal is applied, there is no output (illustrated by the flat yellow line).When the gate driving signal is applied, the triac turns on. There is an output and the triac stays on till the next zero crossing. After this again, there is no output till the next gate drive signal is applied.

Now I’ll show you a few more waveforms, with other initial delays.

Here, the gate is driven 1ms after the zero-crossing:

Fig. 4 - Triac firing with 1 ms delay

Green: Input AC
Yellow: AC Output after phase angle control
Pink: Gate Drive signal

Here, the gate is driven 4ms after the zero-crossing:

Fig. 5 - Triac firing with 4 ms delay

Green: Input AC
Yellow: AC Output after phase angle control
Pink: Gate Drive signal

Here, the gate is driven 5ms after the zero-crossing:

Fig. 6 - Triac firing with 5 ms delay

Green: Input AC

Yellow: AC Output after phase angle control

Pink: Gate Drive signal

Here, the gate is driven 6ms after the zero-crossing:

Fig. 7 - Triac firing with 6 ms delay

Green: Input AC

Yellow: AC Output after phase angle control
Pink: Gate Drive signal

Now, to finish things off, I’ll show you how to find the RMS value of the output voltage.

We first need to know how to relate the firing delay with firing angle. We know that one complete sine wave is 360°. That is 2πradians. We then need to know that the firing angle α = ωt, where ω = 2πf. Since, we’re working with 50Hz here, f=50Hz. Thus, ω = 100π. Just to test this relationship, let’s use t = 0.020 seconds (20ms). Thus α = 100π * 0.020 = 2π, as told before.

So, if we’re firing at a delay of 4ms, that is 4ms after the zero crossing, the firing angle α = 100 π * (4/1000) = 0.4 π (in radians obviously).

The RMS output voltage is found from the relationship:

So, if we are firing after 4ms, (α = 0.4 π), the output RMS voltage is:

Remember, at the beginning, I mentioned that the voltage output is not linearly correlated with the firing angle? This is what I meant. Here, the delay is 4ms. So, the triac is on for 60% of the cycle. But the output RMS voltage is 183.2V - 83% of the input voltage. The lack of direct proportionality is evident here. The reason behind this is the shape of the AC - sinusoidal.

Now, I give you the task of finding the RMS voltage for the other cases mentioned in this tutorial.

If you want to then find power, you can use the relationship P = V²/R to find the power. The assumption here is that the resistance is constant, as was assumed at the beginning of the tutorial. If the resistance is not constant, power will still vary will resistance, just not directly proportionally.

Here in this article, I’ve talked about phase angle control with some background information on triacs. I’ve shown how to implement phase angle control with a PIC and also how to calculate the RMS voltage of the output. I hope I’ve been able to explain this extremely important topic to you clearly and hope that you can now successfully build your own power control circuits using phase angle control with triacs.

Reference Book:
One of the best books for understanding the theory behind phase angle control is "POWER ELECTRONICS - CIRCUITS, DEVICES AND APPLICATIONS" by Muhammad H. Rashid. If you want to learn more about thyristors or phase angle control, I recommend reading this book for more info.

Readmore → AC Power Control with Thyristor Phase Angle Control using triac with PIC16F877A

Saturday, 18 March 2017

How to control LM2596 buck converter with microcontroller

Every now and then someone asks on different forums if there is an way to control cheap LM2596 modules with an Arduino or another microcontroller. I decided to demonstrate one solution that might be basic electronics for some, but still many don’t know about.

Those buck converters will change the output voltage to make the feedback pin, connected to the output via a voltage divider, become 1.25V or so. If feedback is higher, output gets lower and vice versa. If one changes the ratio of resistors in voltage divider, output voltage will change. This is usually done by turning a trimmer resistor with a screwdriver. That is good enough for many applications where voltage will be set only once, but sometimes there is a need to adjust the output voltage more frequently.[ ]

Readmore → How to control LM2596 buck converter with microcontroller

Thursday, 9 March 2017

External Winamp Control Circuit Diagram

Nowadays, winamp have full support to keyboard shortcuts. But some time ago, when Winamp didn’t have this feature, I was thinking in a way I could change the music just by pressing one button, it would make things faster and easier to change songs, specially during games. So I decided to make a external control to it. I found one winamp plugin that shows how to configure a external control using the Serial Port, being able to make 4 or 15 buttons control. I decided to make this, step-by-step, how to do it, hope you enjoy.

Material:

4 push-buttons
SERIAL connector
Connector Box
Cable

Necessary tools:

Soldering iron and accessories

You can put the buttons wherever you want, I decided to put mine in one old diskbox.
I decided to use a network cable to connect the Serial connector to the buttons, because its easier to organize and makes the work simplier and faster.

The scheme:

Making the control:

Looking in the scheme, we see that we have to connect one side of each buttons to one cable, these will be solded in the pin number 4.

After have done the soldering in one side of each button, you must then connect the other side with a cable that goes to the pins of the serial, now however is important that they are connected with the indicated pins (Just follow the scheme) .
Here you can see a picture of my work until now, it looks quite ugly I know, sorry.

Configuring the Software

You must set the COM port you are using, usually normal computers have up to 2 ports, so just select the one you plugged the control.
Select the number of buttons your control have. (In this HowTo, we’d choose the “4 buttons”)
Now you must remap the buttons, its now the time when you’ll see if everything is working. If you are able to remap all the buttons, congrats, its working!!
Its ready, now the last step, you have to configurate what you want the buttons to do. This can be found in the “WINAMP” of the program. There you can setup many different options, like Volume Up, Volume Down, Next Song, Previous Song.
One cool stuff is there in “Type:”, where you can configure the way you wanna the buttons pressing to respond.
Click: Just one click to make it work. Can work with one or double-click.
Down/Up: This will activate the option when you press and a different one when you release the buton.
Turbo: Here you can configure the options for holding the button, usually used for Volume Up and Down.
Clicks + Turbo: You can configure “Clicks” and “Turbo”Option at the same time
Clicks + Hold: You can configure “Clicks” and “Hold” Option at the same time

In the end, I put the buttons in that disk case I told before, and this are the results:

I don’t know if I was clear enought in this HowTo, I will re-check this sometime.
If you liked this, have any correction or advice, please leave a comment!

Source : link

Readmore → External Winamp Control Circuit Diagram

Monday, 6 March 2017

Make a Hi End RF Remote Control Circuit

Building a hi-end remote control device using very few components today looks pretty plausible. The proposed remote control light switch circuit idea provides you with the opportunity of building and owning this amazing device through simple instructions. Moreover the unit provides a 4-bit data to be exchanged between the transmitter and the receiver modules.
This Hi-tech remote control light switch enables you to control four individual lights or any electrical appliance for that matter from any corner of your house remotely using a single tiny remote control hand set. Build the “amazement” right on your workbench.
Imagine switching a light, a fan, washing machine, computer or similar gadgets from any corner of your room without taking a step! Doesn't that sound great? Controlling a particular gadget remotely through a single flick of your finger definitely feels very amusing and amazing too. It also gives you the comfort of doing an act without moving or getting up from a particular position.
The present circuit idea of a remote control light switch enables you controlling not only just a single light but four different electrical gadgets individually using a single remote control hand set.
Let’s try to understand its circuit functioning in details.

Circuit Description:

I have already discussed the wireless control modules through one of my previous articles, let’s summarize the entire description yet again and also learn how simply the stages may be configured into the proposed unit.
The first figure shows a standard transmitter module using the RF generator chip TWS-434 and the associated encoder chip the HOLTEK’s HT-12E.
The IC TWS-434 basically does the function of manufacturing and transmitting the carrier waves into the atmosphere.
However every carrier signal needs modulation for its proper execution, i.e. it needs to be embedded with a data that becomes the information for the receiving end.
This function is done through its complementing part – the HT-12E 4-bit encoder chip. It has got four inputs, which can be triggered discretely by giving them a ground pulse individually. Each of these inputs produces coding which are distinctly different to each other and become their unique signature definitions.
The encoded pulse from the relevant input is transferred to the IC TWS-434 which carries forward the data and modulates it with the generated carrier waves and finally transmits it into the atmosphere.
The above operations take care of the transmitter unit.

The receiver module does the above operations just in the opposite manner.
Here, the IC RWS-434 forms the receiving part of the module; its antenna anticipates the available encoded pulses from the atmosphere and captures them immediately as they are sensed.
The captured signals are relayed forward to the next stage – the signal decoder stage.
Just like the transmitter module, here too a complementing device the HOLTEK’s HT-12D is employed to revert the received encoded signals.
This decoding chip also consists of a 4-bit decoding circuitry and their outputs.
The received data is appropriately analyzed and decoded.
The decoded information gets terminated out through the relevant pin-out of the IC.
This output is in the form of a logic high pulse whose duration depends on the duration of the ground pulse applied to the encoder chip of the transmitter module.
The above output is fed to a Flip-Flop circuit using the IC 4017, whose output is finally used to switch the output load via a relay driver circuitry.
One such flip/flop idea is shown you may construct four of them to access each of the generated 4-bit data discretely and control four gadgets individually.

Whether you use it as a remote control light switch or to control many more appliances……the option is all yours.

Readmore → Make a Hi End RF Remote Control Circuit

Wednesday, 1 March 2017

Stepper motor control using NE555

Readmore → Stepper motor control using NE555

Tuesday, 21 February 2017

Control Interface via PC Keyboard

One of the more difficult aspects when making a control or security system that uses a PC (a burglar alarm using a PC, for example), is the connection of the sensors to the computer. In addition to typically requiring specialist interface expansion boards, the writing of the program that includes interrupts is often also an insurmountable obstacle. But when only a simple system is concerned consisting of, for example, four light barriers or, if need be, trip wires giving a digital on/off signal when uninvited guests enter, then a much cheaper but nevertheless effective interface is possible.

For this interface we use an (old) computer keyboard. This contains as many switches as there are keys. These switches are scanned many times per second in a matrix in order to detect the potential press of a key. The number of columns is usually eight (C0–C7 in the schematic); the number of rows varies for each type of keyboard and can range from 14 to 18 (R0–R17 with the H T82K 28A keyboard encoder mentioned in the example). To each switch there is a single column and a single row connection.

Circuit diagram :

Control Interface via PC Keyboard Circuit Diagram

The intention of the circuit is that sensor A will ‘push’ the letter A, when it senses something. This requires tracing the keyboard wiring to figure out which column and which row is connected to the A key. One of the four analogue switches from the familiar CD4066 CMOS IC is then connected between these two connections; that is, in parallel with the mechanical A key on the keyboard. When the Control-A input of the CD4066 is activated by sensor A, the letter A will be sent to the computer by the key-board. The PC can then act appropriately, for example by entering the alarm phase.

The system is not limited to (burglar) detection using a PC. The remote control of a TV set or other electronic devices can also be operated with a 4066 in the same way; for example to scan through a number of TV channels in a cyclical fashion. To do this, you could, for example, shunt the ‘next channel’ button using one of the 4066 switches, which itself is activated by a 1-Hz square wave generator.

In the schematic only switches A and B of the CD4066 are connected to the keyboard. You can, of course, use all four of the switches and if you need more than four you can use multiple CD4066 ICs. The indicated wiring between the keyboard IC and the 4066 is an example only, and each ‘typed’ letter has to be determined by the user for the specific keyboard that is used. It is important that each CD4066 switch is always connected between a row- and a column connection. The output signal from the sensors has to be suitable for the CD4066 and the power sup-ply voltage of 5 volts used by the keyboard. The power supply for the CD4066 may be obtained from the keyboard.

Author : Jacob Gestman Geradts - Copyright : Elektor

Readmore → Control Interface via PC Keyboard

Wednesday, 15 February 2017

Simple Remote Control Mains Switch

As the only electronics engineer in my =family and circle of friends, it is some-times not possible to evade an appeal for help. This time the request came from a friendly elderly lady in a retirement home. In her room the light switch by the door and the pull cord above the bed operate the light fitting on the ceiling in the middle of the room. However, she would prefer that her standing lamp was operated by these switches instead, since she does not actually have a light fitting mounted on the ceiling. This standing lamp has an on/of f switch in the power cord and is plugged into a power point. However, it stands rather far from the bed so that she always has to find her way in the dark. A wireless operated power point is not really a consideration, because it is just a matter of time before the remote is lost. Or maybe not?

Remote Control Mains Switch Circuit Diagram :

Behold a feasible circuit. Buy a wireless power point and an enclosure that is big enough for the remote control and a small piece of prototyping board. On the proto-typing board build the circuit according to the accompanying schematic and (care-fully) open the remote control and solder wires to the push buttons for ‘on’ and ‘off’. Measure if these are polarised and if that is the case connect them to the 4N25 opto-couplers as shown in the schematic, where pin 5 has a higher voltage than pin 4.

The operation is as follows. The lady operates the pull cord or light switch to turn the light on. This causes the mains voltage to be applied to the transformer. The relay is activated which charges C1. While C1 charges, a small current flows through optocoupler 1. The result is that the ‘on’ button on the remote control is pressed. The remote control switches the corresponding power point on and to which the standing lamp is connected. The standing lamp will therefore now turn on. Capacitor C2 is charged at the same time. If the lady pulls the cord again, or if she operates the switch near the door, the relay will de-energise and C2 discharges across optocoupler #2. This operates the ‘off’ contact of the remote control and the light goes out.

The remote control continuous to operate from its normal battery and the white enclosure is attached to the ceiling in place of the light fitting. Diode D1 ensures that C1 is discharged when the relay de-energises. D2 ensures that C2 cannot discharge across the relay, but only across optocoupler 2.

Author : Jaap van der Graaff - Copyright :Elektor

Readmore → Simple Remote Control Mains Switch

Wednesday, 8 February 2017

Simple TV Remote Control Jammer Circuit Diagram

This is the Simple TV Remote Control Jammer Circuit Diagram. Do you have an incessant channel hopper that is driving you crazy? Or perhaps you simply want to enforce your own selections. The TV Remote Control Jammer will do the trick.

Simple TV Remote Control Jammer Circuit Diagram

This circuit is a redo of an older design which is not effective on modern remotes. Modern remote controls are hard to jam but with a little care this circuit will do the job. The circuit is just a flasher operating at 40 kHz which is the carrier frequency used by common remote controls. The strong 40 kHz infrared flashing interferes with the signal from the remote.

The 50k potentiometer is adjusted to achieve a 40 kHz flash rate (around 20 kohms) and this adjustment is fairly critical. When it is set properly and the LEDs are pointed directly at the receiver's photodiode, the remote control will stop working. The LEDs are operating at about 30 mA when on but the duty cycle is low and the circuit only draws about 7 mA.

Trouble may be encountered if the frequency is set wrong, the LEDs are not pointed correctly, or if the remote is a real brute. More light may be had by adding another resistor and diode string from the collector to the switch but the most likely problem is the frequency adjustment. Use a 10-turn pot and adjust it slowly while changing channels. Or use a frequency counter or oscilloscope to set the frequency, if possible. Make sure that the current drain is about 7 mA - if not, check the polarity of the diodes. A photodiode infrared receiver is handy for checking the light output and comparing it to the remote's.

Readmore → Simple TV Remote Control Jammer Circuit Diagram

Tuesday, 31 January 2017

Vice Control Music Outlet with SL517A

This is Vice Control Music Outlet circuit using SL517A, this electronic circuit project build a very easy. The circuit is shown in Figure, and it is composed of acoustic sensor, voice control IC, relay control circuit, song voice circuit and AC buck rectifier circuit.

Vice Control Music Outlet Circuit using SL517A:

Voice control IC uses SL517A which contains high-gain amplifier, bistable flip-flop and buffer output level, and it has two packages of dual in-line and black ointment. Its internal functional block diagram is shown as below.

Readmore → Vice Control Music Outlet with SL517A

Saturday, 14 January 2017

H bridge Control the Direction of Rotation for DC motor Circuit Diagram

This circuit can control the direction of a DC motor., It has many applications that are necessary to operate a motor in both directions, clockwise and counter-clockwise (forward and backward). One way to accomplish this is to start the engine in a circuit arrangement of transistors called H-bridge. H bridge is an electronic circuit which enables a voltage is applied across a load in either direction. This circuit is often used in robotics and other applications to allow DC motors to become bi-directional.

H-bridge Control the Direction of Rotation for DC motor Circuit Diagram

List of components

PARTS LIST
R1, R2, R3, R4 220Ω
R5, R6, R7, 1K Ohm
D1, D2, D3, D4 1N4001
D5, D6 LED
Q1, Q2 2SD313
Q3, Q4 2SB507
PB1, PB2 switch
M1 12V DC MOTOR

In this circuit usually PB1 and PB2 are open. Thus, the bases of the transistors are grounded. Hence Q3 and Q4 are turned on, Q1 and Q2 are turned off. The voltages at both terminals of the motor is the same and thus the engine is switched off. Similarly, when both PB1 and PB2 are "on" motor is turned off. The LEDs indicate the direction of motor rotation.

Readmore → H bridge Control the Direction of Rotation for DC motor Circuit Diagram

Wednesday, 11 January 2017

Digital Volume Control

This digital volume control has no pot to wear out and introduces almost no noise in the circuit. Instead, the volume is controlled by pressing UP and DOWN buttons. This simple circuit would be a great touch to any home audio project.

Parts:

Part	Total Qty.	Description
C1	1	0.1uf Ceramic Disc Capacitor
U1	1	DS1669 Digital Pot IC (See Notes)
S1, S2	2	Momentary Push Button Switch
MISC	1	Board, Wire, Socket For U1

Notes:

1. U1 is available from Dallas Semiconductor.

2. S1 turns the volume up, S2 turns it down.

3. The input signal should not fall below -0.2 volts.

4. Using a dual polariity power supply (+-5V works fine) will cure most clipping problems. You will have to check the data sheet for the correct pins to connect your voltages.

Readmore → Digital Volume Control

Tuesday, 10 January 2017

8 Relay Control Circuit

8 Relay Control Circuit
R1-8=4.7 Kohms T1-8= BD139 (R1-8=15 Kohms if T1-8=BD679)
RL1-8=6V-24V dc Relay D1-8=1N4148

Readmore → 8 Relay Control Circuit

Friday, 6 January 2017

Lights Control for Model Cars Circuit Diagram

The author gave his partner a radio controlled (RC) model car as a gif t. She found it a lot of fun, but thought that adding realistic lights would be a definite improvement. So the author went back to his shed, plugged in his soldering iron, and set to work equipping the car with realistic indicators, headlights, tail lights and brake lights.

Lights Control for Model Cars Circuit Diagram

The basic idea was to tap into the signal from the radio control receiver and, with a bit of help from a microcontroller, simulate indicators using flashing yellow LEDs and brake lights using red LEDs. Further red LEDs are used for the tail lights, and white LEDs for the headlights. Connectors JP4 and JP5 (channel 0) are wired in parallel, as are JP6 and JP7 (channel 1), allowing the circuit to be inserted into the servo control cables for the steering and drive motor respectively. The ATtiny45 micro-controller takes power from the radio receiver via diode D1. T1 and T2 buffer the servo signals to protect IC1’s inputs from damage.

IC1 analyses the PWM servo signals and gen-erates suitable outputs to switch the LEDs via the driver transistors. T3 drives the two left indicators (yellow), T4 the two right indica-tors, and T5 the brake LEDs (red). The red tail lights (JP2-8 and JP2-8) and the white head-lights (JP2-9 and JP2-10) are lit continuously. The brake lights are driven with a full 20 mA, so that they are noticeably brighter than the tail lights, which only receive 5 mA. If you wish to combine the functions of tail light and brake light, saving t wo red LEDs, sim-ply connect pin 10 of JP2 to pin 14 and pin 12 to pin 16. Then connect the two combined brake/tail LEDs either at JP2-5 and JP2-6 or at JP2-7 and JP2-8.

JP3 is provided to allow the use of a separate lighting supply. This can either be connected to an additional four-cell battery pack or to the main supply for the drive motor. The val-ues given for resistors R8 to R17 are suitable for use with a 4.8 V supply. JP2 can take the form of a 2x10 header.

As usual the sof t ware is available as a free download from the Elektor web pages accom-panying this article[1], and ready-programmed microcontrollers are also available. The microcontroller must be taught what servo signals correspond to left and right turns, and to full throttle and full braking. First connect the fin-ished circuit to the radio control electronics in the car, making sure everything is switched of f. Fit jumper JP1 to enable configuration mode, switch on the radio control transmit-ter, set all proportional controls to their cen-tre positions, and then switch on the receiver. The indicator LEDs should first flash on both sides. Then the car will indicate left for 3 s: during this time quickly turn the steering on the radio control transmitter fully to the left and the throt tle to full reverse (maximum braking).

Hold the controls in this position until the car starts to indicate right. Then set the controls to their opposite extremes and hold them there until both sides flash again. Now, if the car has an internal combustion engine (and so cannot go in reverse), keep the throttle control on full; if the car has an electric motor, set the throttle to full reverse. Hold this position while both sides are flashing. Configuration is now complete and JP1 can be removed. If you make a mistake during the configuration process, start again from the beginning.

Author: Manfred Stratmann - Copyright : Elektor

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Saturday, 31 December 2016

UHF FM Remote Control Receiver Circuit

The receiver is intended primarily for use with the remote control UHF transmitter described in the preceding article.
It is a super-regenerative type with an active RF amplifier, T1. The antenna signal is applied to the input inductor via a BNC socket, K1. The input circuit is tuned by trimmer C4. The amplified RF signal is applied to the input of the super-regenerative stage based on transistor T2. Although the oscillator is, strictly speaking, not tuned, it will lock on to the amplified RF signal applied via coupling capacitor C7. The low-frequency modulation component is extracted from the oscillator signal with the aid of low-pass filter, R6-R7-C12-R8-C13. The signal level at the demodulator output is 50 to 800 mVpp, so that further amplification is required·before the signal can be applied to a digital input. The inductors in the RF amplifier input and output are made from 1 mm dia. silver-plated wire. The length of the pieces of wire is indicated by the component overlay. The wires run at a height of about 3 mm above the board surface. Note that the stator terminal of C4 is bent upwards and soldered direct to the input inductor. The same goes for junction C6-C7, which is soldered ‘in the air‘, directly op to the hot end of the inductor wire. Inductor L1 consists of 12 turns of 0.6-mm dia. enamelled copper wire. Its internal diameter is 3 mm. Each of chokes g and L3 consists of 4 turns of 0.2-mm dia enamelled copper wire through a 3 mm long ferrite bead. Capacitor C8 is a surface-mount technology (SMT) type which is fitted at the solder side of the board, as are the BFG65 and the BFQSO. The type indica- tion printed on the transistors is legible from the component side of the board. As indicated by the dashed lines on the component overlay, the super-regenerative section of the circuit must be screened from the rest. To do this, it is best to solder a 20 mm high tin plate box on to the PCB as indicated.

For the transmitter circuit : UHF FM Remote Control Transmitter Circuit

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Thursday, 22 December 2016

Lights Control for Model Cars Circuit Diagram

Lights Control for Model Cars Circuit Diagram

Author: Manfred Stratmann - Copyright : Elektor

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Tuesday, 20 December 2016

Control circuit of star delta starter

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Friday, 9 December 2016

0 30V Stabilized Variable Power Supply with Current Control

This is high quality stabilized power supply circuit diagram. You will able to adjust the output voltage from 0 volt up to 30 volt DC. You also able to adjust the current output value from 0.002 A to 3 A. This variable power supply incorporates an electronic output current limiter that effectively controls the output current from a few mA (2 mA) to the maximum output of 3 A that the circuit can produce.

Component list:
R1 = 2,2 KOhm 1W
R2 = 82 Ohm 1/4W
R3 = 220 Ohm 1/4W
R4 = 4,7 KOhm 1/4W
R5, R6, R13, R20, R21 = 10 KOhm 1/4W
R7 = 0,47 Ohm 5W
R8, R11 = 27 KOhm 1/4W
R9, R19 = 2,2 KOhm 1/4W
R10 = 270 KOhm 1/4W
R12, R18 = 56KOhm 1/4W
R14 = 1,5 KOhm 1/4W
R15, R16 = 1 KOhm 1/4W
R17 = 33 Ohm 1/4W
R22 = 3,9 KOhm 1/4W
RV1 = 100K trimmer
P1, P2 = 10KOhm linear pontesiometer
C1 = 3300 uF/50V electrolytic
C2, C3 = 47uF/50V electrolytic
C4 = 100nF polyester
C5 = 200nF polyester
C6 = 100pF ceramic
C7 = 10uF/50V electrolytic
C8 = 330pF ceramic
C9 = 100pF ceramic
D1, D2, D3, D4 = 1N5402,3,4 diode 2A – RAX GI837U
D5, D6 = 1N4148
D7, D8 = 5,6V Zener
D9, D10 = 1N4148
D11 = 1N4001 diode 1A
Q1 = BC548, NPN transistor or BC547
Q2 = 2N2219 NPN transistor
Q3 = BC557, PNP transistor or BC327
Q4 = 2N3055 NPN power transistor
U1, U2, U3 = TL081, operational amplifier
D12 = LED diode

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Sunday, 4 December 2016

0 30V Stabilized Variable Power Supply with Current Control

Readmore → 0 30V Stabilized Variable Power Supply with Current Control

Tuesday, 29 November 2016

3 Band Tone Control Circuit

3 Band Tone Control circuit uses an op-amp as an amplifier end. Tone Control circuit is a regulator of tone bass, midrange and treble or 3 band called because it can set the three tones. Filter circuit is applied to the series of "Tone Control 3 band" This type baxandal like the title of this article.

Results filtering regulator tone or tone control baxandal type is good, because there is no signal level is wasted directly into the ground. Range frequency tones generated from Tone Control 3 band was determined by the configuration of the R and C of the filter section baxandal. As an amplifier on Tone Control The set of three band use traditional IC LF351 has slewrate high and high input impedance. For more details, series 3 Band Tone Control as follows.

Figure Series 3 Band Tone Control

3 Band Tone Control circuit above using LF351 Op-Amp is used to strengthen the signal after filtering by the filter process baxandal. Level tone Bass, Midrange and Treble settings are determined by potensio R1, R2 and R3. Frequency filter in the circuit above baxandal to 50 Hz bass tone, tone Midrange 1 KHz and 10 KHz for Treble tone.

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Tuesday, 22 November 2016

LBL Activated Remote Control Circuit Diagram

This is the simple Laser Beam Light Activated Remote Control Circuit Diagram. The following post illustrates a simple light toggled/operated remote control circuit, which can be activated by an ordinary flashlight or more effectively through a laser beam unit (key chain type).

LBL Activated Remote Control Circuit Diagram

The circuit idea may be understood with the below mentioned points:

Transistor T1 alnog with R3, C6 and the LDR itself forms a simple light sensor stage.
The LDR is connected across the base of the transistor and the positive supply such that when light falls over the LDR, T1 receives the required base bias and conducts.
When T1 conducts, the high potential at pin 14 of IC1 is pulled to logic low. However since a logic low wouldn't effect pin#14, IC1 does not respond as yet.
The moment light on the LDR is switched OFF, T1 is switched OFF and pin#14 now instantly receives a subsequent logic high via R5.....now IC1 responds, and shifts it's output from pin#3 to pin#2. This makes pin#3 logic low, activating T2, and the preceding relay driver stage.
The above condition persists until the LDR is illuminated again with a flashlight or with a laser beam.
The above operation alternately toggles the output ON and OFF providing the required toggling actions to the connected load.
The LDR must be covered inside an opaque pipe, about an inch long so that the ambient light stays obstructed from the LDR.
The angle of the pipe should be kept in a such a way that it facilitates easy focusing of the light beam toward the LDR.
C6 ensures that the system does not respond to accidental spurious light beams in case it finds its way inside the pipe, and over the LDR.

Parts List

R3,R4,R5,R6,R7 = 2K2
T1 = BC547,
T2 = BC557
IC1 = 4017
IC2 = 7812
ALL DIODES = 1N4007
C6,C7 = 10uF/25V
C8 = 1000uF/25V
C10 = 0.1uF

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