Safe Oscillator For Watch Crystals circuit with explanation

This circuit was developed to allow watch crystals to be used in an existing CMOS oscillator circuit that was to run from a 12V supply. The problem is that these crystals only work up to a supply voltage of about 6V. Any more than that and the crystal will be over-driven, causing it to shatter. This circuit solves the problem by using LEDs 1 & 2 and a 470nF capacitor (C3) to limit the drive to the crystal to about 4V peak-to-peak. Note that it may be necessary to adjust C1 & C2 to ensure reliable start-up and stable oscillation with some crystals. However, the C1:C2 ratio should be maintained. As a bonus, the two LEDs both glow, giving a visual indication that the oscillator is working.

The relatively high values used here for capacitors C1 & C2 will load the crystal, which means that the oscillator will run at less than the nominal crystal frequency (32.768kHz).
Author: Duncan Graham – Copyright: Silicon Chip Electronics
Read more : http://www.extremecircuits.net/2010/06/safe-oscillator-for-watch-crystals_14.html

1HZ Standard digital clock circuit with explanation

This is a standard digital clock circuit,frequency size 1 Hz or 2 Hz. It can be used in the normal clock circuit. It consists of IC-4060 and IC-4013, the IC-4060 single acting Oscillator and Counter. of the frequency determined by the resistor and external capacitor.In the circuit, IC 4060 is a standard frequency generator with quartz crystal. The adjustment period with C2, and counter circuits within the IC 4060 will be only 2 Hz frequency dividing out the pin 3. The IC-4015 in the style of TF / F to divide two of the Clock signal frequency is out 1 Hz.

Beat-frequency Oscillator Simple Metal Detector Schematic

This simple metal detector requires alone a scattering of apparatus and an evening’s work. Congenital about a cmos4011 IC, is actual able-bodied and versatile. The 250 kHz advertence oscillator is congenital with two gates (U1/1 and U1/2), C1, R1 and P1. The chase oscillator uses alone one aboideau (U1/3), two capacitors and the chase coil. The outputs of the two oscillators are fed to the fourth aboideau acting as a mixer and filtered with C4.

After assembly, affix the headphones and boring about-face P1. The angle will get lower until it disappears. Continuing to circle P1 in the aforementioned administration will account the angle to acceleration again. The point at witch the angle is the everyman and disappears is alleged “zero beat”. If you can not get this aught exhausted abundance for the absolute about-face of P1 you may accept to baddest altered ethics for C1.

Turn P1 abutting to the aught exhausted position, again move the chase braid abreast a brownish object. The accent should change, depending on the admeasurement and ambit of the metal.

Note that this simple detector’s achievement is not commensurable to added avant-garde bartering products. It will alone ascertain about ample brownish altar at a abbreviate distance. Coins and added baby altar will be abundant harder to find!

Here the Beat-frequency Oscillator Simple Metal Detector Schematic Part List :

• U1: CD4011 (Quad 2-input NAND Gate)
• U2: LM78L05 (5V Regulator IC)
• R1: 2.2k 5% resistor
• R3: 330k 5% resistor
• R4: 270k 5% resistor
• R5: 1k 5% resistor
• C1: 390pF NPO capacitor
• C2, C3: 10nF
• C4: 100nF
• C5: 100uF/16V electrolytic
• C6: 220uF/16V electrolytic
• C7: 100nF ceramic
• P1: 4.7k lin. potentiometer
• L1: 22cm diameter, 14 turns, AWG 26
• K1: SPDT toggle switch
• J1: Headphone jack 1/4 or 1/8 inch

High Output Power RF Push-Pull MOSFET Oscillator

With the circuit shown here you can create high frequency electromagnetic waves with very high output power.

Possible applications are experiments with wireless power transmission, RFID Transponder, tesla coils and the like.

Dependent on the coil, capacitor and cooling of the transistors output power in the range of 20W and more can be obtained.

At short distances, other electronic circuits may be disturbed or even destroyed. Broadcasting, RFID, AntiTheft, Wlan, medical appliances (pacemakers!) can be disturbed in a large area!

Never operate this circuit without taking precautions !

It may be illegal to operate in your Country!

The Circuit:

It is a standard Push Pull Oscillator, based on Power Mosfet Transistors.

The PCB provides mounting space for two SK104 heatsinks, this allows for remarkable output power for such a small device.

For a high resolution layout, click on the Image!

Component Values:

Operation Voltage is about 15V DC

If you wish to use smaller operating voltages, you must increase R2 and R3. Oscillation starts when the voltage drop across R2 resp. R3 reaches the MOSFET’s thresold Voltage, approx. 4..6V

Mosfet: IRF510

R1, R4 100k

R2, R3 27K

C4, C5 100u

C1 choose for your desired frequency

C2,C3 ca 10% of C1

D1,D2 15V Z-Diodes

A PushPull Oscillator requires a coil with a Center Tap. For my tests i used 12 Turn 1mm insulated Copper Wire, ca 40mm Diameter.

The Center Tap is connected to PAD1

A Frequency Range from 200kHz to 10MHz was generated using this coil.

The Resonance Frequency of the is calculated by (approx)

Important!

The Capacitors, especially C1 should be low ESR, otherwise they will heat up and be destroyed!

A LED connected to a small receiver coil lit up at about 20cm distance. At 10 cm, it became hot and was destroyed eventually!

Source:skemarangkaian.com

10.58 to 10.74 MHz VFO Oscillator Circuit

Figure 1, below, shows the 10.58 to 10.74 MHz VFO oscillator circuit. Yes, this is the same circuit that was presented last time, but I’ve re-drawn it to show the Colpitts oscillator more clearly. “L” is approximately 1.5 uH; 19 turns in a T50-6 core (yellow). The value of C6 is found experimentally. I used 69 pF (a 47 pF and a 22 pF in parallel). More about this during check-out.

10.58 to 10.74 MHz VFO Oscillator Circuit

“L” and the V V C along with C6 make up the parallel-tuned circuit that determines the frequency of the VFO. The V V C is an MV2104. Capacitors marked with an asterisk must be silvered mica, COG, or NPO.

You might wonder how the component values for the resonant circuit are determined. Well, when Jupiter is aligned with Mars, and Mercury is on the cusp of a new moon, if the inductive reactance equals the capacitive reactance, then we have a resonant circuit. For any given frequency there are endless combinations of L and C that will produce a resonant circuit. Experience shows that variable capacitors and V V C’s in the 5 pF to 300 pF range are altogether practical. Combine this with the fact that a 1.5 uH coil and a 150 pF capacitor resonate near the frequency of interest, and you have the component values for this VFO’s resonant circuit. You can find formulas for figuring all this out in your Handbook, if you like to do arithmetic. The component values actually used in the circuit take into account “stray” inductance and capacitance that occurs in the real world. More about this during check-out.

RESONANT CIRCUITS are fascinating critters! While I’m NOT going to get into a theoretical discussion, there are some fundamental characteristics of resonant circuits that you (and I) should keep in mind when building VFO’s, filters, RF amplifiers, etc.

Two types of resonant circuits are commonly used: series resonant circuits and parallel resonant circuits, as shown below. Here are two important things to keep in mind: PARALLEL resonant circuits attenuate the flow of AC current at the resonant frequency (and pass all other frequencies); SERIES resonant circuits pass AC current at the resonant frequency (and attenuate all other frequencies).

Simple audio oscillator circuit and explanation

A very simple audio oscillator electronic project can be designed using two transistors and some other electronic parts . As you can see in the circuit diagram , this audio tone oscillator circuit require a 9 volts DC power supply .
R1 and C1 components can be a variable type . By modifying values of R1 and C1 will vary the tone .
 For this audio oscillator circuit you can use almost any transistor . To power this audio oscillator you’ll need to use a 9 volt battery or a 9 volt DC power supply .

using a PIC18F2620 Etching pan rocker

Some people consider PCB etching as a tedious task. One has to have extra care in handling the etchant – which stains, one needs to keep an eye on it to avoid over etching and one needs to rock the etching pan to speed up the etching process.

To make life a lot easier for hobbyists Graham came up with an ingeniously simple way of automating the rocking motion for the etching pan. He attached a servo motor on a pivot where the etching pan can tilt on both directions. Using a PIC18F2620 to send digital pulses he controls the back and forth motion of the servo which in turn gives the etching pan a rocking motion. Rock A By etching pan.

Transistor Schmitt Trigger Oscillator The Schmitt Trigger oscillator below employs 3 transistors, 6 resistors and a capacitor to generate a square wa

The Schmitt Trigger oscillator below employs 3 transistors, 6 resistors and a capacitor to generate a square waveform. Pulse waveforms can be generated with an additional diode and resistor (R6). Q1 and Q2 are connected with a common emitter resistor (R1) so that the conduction of one transistor causes the other to turn off. Q3 is controlled by Q2 and provides the squarewave output from the collector.

In operation, the timing capacitor charges and discharges through the feedback resistor (Rf) toward the output voltage. When the capacitor voltage rises above the base voltage at Q2, Q1 begins to conduct, causing Q2 and Q3 to turn off, and the output voltage to fall to 0. This in turn produces a lower voltage at the base of Q2 and causes the capacitor to begin discharging toward 0. When the capacitor voltages falls below the base voltage at Q2, Q1 will turn off causing Q2 and Q3 to turn on and the output to rise to near the supply voltage and the capacitor to begin charging and repeating the cycle. The switching levels are established by R2,R4 and R5. When the output is high, the voltage at the base of Q2 is determined by R4 in parallel with R5 and the combination in series with R2. When the output is low, the base voltage is set by R4 in parallel with R2 and the combination in series with R5. This assumes R3 is a small value compared to R2. The switching levels will be about 1/3 and 2/3 of the supply voltage if the three resistors are equal (R2,R4,R5).

There are many different combinations of resistor values that can be used. R3 should low enough to pull the output signal down as far as needed when the circuit is connected to a load. So if the load draws 1mA and the low voltage needed is 0.5 volts, R3 would be 0.5/.001 = 500 ohms (510 standard). When the output is high, Q3 will supply current to the load and also current through R3. If 10 mA is needed for the load and the supply voltage is 12, the transistor current will be 24 mA for R3 plus 10 mA to the load = 34 mA total. Assuming a minimum transistor gain of 20, the collector current for Q2 and base current for Q3 will be 34/20 = 1.7 mA. If the switching levels are 1/3 and 2/3 of the supply (12 volts) then the high level emitter voltage for Q1 and Q2 will be about 7 volts, so the emitter resistor (R1) will be 7/0.0017 = 3.9K standard. A lower value (1 or 2K) would also work and provide a little more base drive to Q3 than needed. The remaining resistors R2, R4, R5 can be about 10 times the value of R1, or something around 39K.

The combination of the capacitor and the feedback resistor (Rf) determines the frequency. If the switching levels are 1/3 and 2/3 of the supply, the half cycle time interval will be about 0.693*Rf*C which is similar to the 555 timer formula. The unit I assembled uses a 56K and 0.1 uF cap for a positive time interval of about 3.5 mS. An additional 22K resistor and diode were used in parallel with the 56K to reduce the negative time interval to about 1 mS.

In the diagram, T1 represents the time at which the capacitor voltage has fallen to the lower trigger potential (4 volts at the base of Q2) and caused Q1 to switch off and Q2 and Q3 to switch on. T2 represents the next event when the capacitor voltage has risen to 8 volts causing Q2 an Q3 to turn off and Q1 to conduct. T3 represents the same condition as T1 where the cycle begins to repeat. Now, if you look close on a scope, you will notice the duty cycle is not exactly 50% This is due to the small base current of Q1 which is supplied by the capacitor. As the capacitor charges, the E/B of Q1 is reverse biased and the base does not draw any current from the capacitor so the charge time is slightly longer than the discharge. This problem can be compensated for with an additional diode and resistor as shown (R6) with the diode turned around the other way.

Source

Latest Alternate 555 Oscillator

This is a slightly simpler circuit than the one above. The circuit uses just one resistor and one capacitor with the 555 timer IC to create a stable and reliable oscillator with an output that it a true squarewave.
The formula for calculating the frequency is:

f=1/(1.4*R*C).

The values in the formula are expressed in ohms, farads, seconds and hertz. This formula is much simpler than that of the previous circuit. With the values shown on the circuit, the frequency is calculated as 1050Hz, but like the previous circuit, this arrangement can operate at frequencies up to around 500kHz.
…

Read More Source: http://www.geocities.com/electronics3456/555circuits.html
Thank you.

88-108 MHz Voltage Controlled Oscilator for PLL Controller This Circuit will explain the PLL unit and the VCO (Voltage Controlled Oscillator) which w

88-108 MHz Voltage Controlled Oscilator for PLL Controller

This Circuit will explain the PLL unit and the VCO (Voltage Controlled Oscillator) which will create the FM modulated RF signal up to 400mW. the schematic to follow my function description. The main oscillator is based around the transistor Q1. This oscillator is called Colpitts oscillator and it is voltage controlled to achieve FM frequency modulation) and PLL control.

Q1 should be a HF transistor to work well, but in this case I have used a cheap and common BC817 transistor which works great. The oscillator needs a LC tank to oscillate properly. In this case the LC tank consist of L1 with the varicap D1 and the two capacitor (C4, C5) at the base-emitter of the transistor. The value of C1 will set the VCO range.

The large value of C1 the wider will the VCO range be. Since the capacitance of the varicap (D1) is dependent of the voltage over it, the capacitance will change with changed voltage. When the voltage change, so will the oscillating frequency. In this way you achieve a VCO function. You can use many different varicap diod to get it working. In my case I use a varicap (SMV1251) which has a wide range 3-55pF to secure the VCO range (88 to 108MHz).

Inside the dashed blue box you will find the audio modulation unit. This unit also include a second varicap (D2). This varicap is biased with a DC voltage about 3-4 volt DC. This varcap is also included in the LC tank by a capacitor (C2) of 3.3pF. The input audio will passes the capacitor (C15) and be added to the DC voltage. Since the input audio voltage change in amplitude, the total voltage over the varicap (D2) will also change. As an effect of this the capacitance will change and so will the LC tank frequency.

You have a Frequency Modulation of the carrier signal. The modulation depth is set by the input amplitude. The signal should be around 1Vpp. Just connect the audio to negative side of C15. Now you wonder why I don't use the first varicap (D1) to modulate the signal? I could do that if the frequency would be fixed, but in this project the frequency range is 88 to 108MHz.

If you look at the varicap curve to the left of the schematic. You can easily see that the relative capacitance change more at lower voltage than it does at higher voltage. Imagine I use an audio signal with constant amplitude. If I would modulated the (D1) varicap with this amplitude the modulation depth would differ depending on the voltage over the varicap (D1). Remember that the voltage over varicap (D1) is about 0V at 88MHz and +5V at 108MHz. By use two varicap (D1) and (D2) I get the same modulation depth from 88 to 108MHz.

Now, look at the right of the LMX2322 circuit and you find the reference frequency oscillator VCTCXO. This oscillator is based on a very accurate VCTCXO (Voltage Controlled Temperature controlled Crystal Oscillator) at 16.8MHz. Pin 1 is the calibration input. The voltage here should be 2.5 Volt. The performance of the VCTCXO crystal in this construction is so good that you do not need to make any reference tuning.

A small portion of the VCO energy is feed back to the PLL circuit through resistor (R4) and (C16). The PLL will then use the VCO frequency to regulate the tuning voltage. At pin 5 of LMX2322 you will find a PLL filter to form the (Vtune) which is the regulating voltage of the VCO. The PLL try to regulate the (Vtune) so the VCO oscillator frequency is locked to desired frequency. You will also find the TP (test Point) here.

The last part we haven't discussed is the RF power amplifier (Q2). Some energy from the VCO is taped by (C6) to the base of the (Q2). Q2 should be a RF transistor to obtain best RF amplification. To use a BC817 here will work, but not good.

The emitter resistor (R12 and R16) set the current through this transistor and with R12, R16 = 100 ohm and +9V power supply you will easy have 150mW of output power into 50 ohm load. You can lower the resistors (R12, R16) to get high power, but please don't overload this poor transistor, it will be hot and burn up… Current consumption of VCO unit = 60 mA @ 9V.

Printed Circuit Board (PCB.pdf)
This is how the real board should look when you are going to solder the components.
It is a board made for surface mounted components, so the cuppar is on the top layer.

Parts List
100 = R7, R12, R16
330 = R4
1k = R1, R2, R3, R10
3.3k = R11
10k = R5, R6, R14, R17
20k = R13
43k = R9
100k = R8, R15
3.3pF = C2, C16
15pF = C4, C6
22pF = C5
1nF = C1, C3, C8, C17, C22, C23
100nF = C7, C9, C11, C12, C13, C14, C19, C20
2.2uF = C15, C18
220uF = C10, C21
L1 = 3 turns diam 6.5mm (Everything from 6 to 7 mm will work good!)
L2, L3, L4 = 10uH
D1, D2 = SMV1251
Q1 = BC817-25
Q2 = BFG193
X1 = 16.800 MHz VCTCXO Reference oscillator
V1 = 78L05
IC1 = LMX2322

Source