Tagged Questions

A device or circuit that generates an AC signal at a certain frequency.

2k views

Why does a faster clock require more power?

If you overclock a microcontroller, it gets hot. If you overclock a microcontroller, it needs more voltage. In some abstract way it makes sense: it is doing more computation, so it needs more energy ...
3k views

Crystals, Oscillators, and Resonators. What the difference?

I am trying to figure out the difference between crystals, oscillators, and resonators. I'm starting to grasp it but I still have some questions. From my understanding, an oscillator is built from a ...
544 views

Low power, low voltage, slow (0.1Hz) oscillator?

I had the opportunity to analyze a very interesting circuit today using a programmable unijunction transistor as a timer. The power supply varies, and the circuit must operate on under 10uA of ...
4k views

What's the easiest/cheapest variable-frequency sine wave oscillator?

A Google search will give you a few billion ideas. Which is the simplest/easiest/cheapest that you know of? Generating a square wave and then filtering out the harmonics isn't a good solution unless ...
178 views

Can vibrations of quite an appreciable amplitude affect the clock signal of a crystal oscillator?

I'm very curious to know as I was told that these crystals are electro-mechanical transducers. So theoretically any excess mechanical vibration should result in an error, right?
191 views

Ring oscillator not oscillating

Inspired by this blog post, I decided to put together a simple ring oscillator that transitions through 3 different LEDs. My schematic is almost identical the one in the blog post except that I used ...
5k views

How to design the capacitors used with Crystal Oscillators?

I have seen circuits involving crystal oscillators connecting two capacitors between each of the crystal legs and ground. I would like to know how to design the value of these capacitors for different ...
186 views

Why does this circuit oscillate?

The circuit below is an oscillator. When I simulate it with ltspice, it does indeed generate a waveform (although it doesn't seem to be a very pure sine wave). What I fail to understand is why it ...
888 views

My 12 MHz crystal does not oscillate

I am having trouble with a board I have had fabricated. The processor is an NXP LPC1788 Cortex-M3. I am using a 12 MHz external crystal to clock the processor as recommended in the datasheet. ...
2k views

How do I use a quartz crystal in an oscillator?

How can I get a quartz crystal to make square waves at 4.096MHz? So far I have the 4.096MHz quartz crystal and this schematic I saw: Where can you find an amplifier with a single input and what ...
360 views

Oscillator Driven LED - Not Oscillating

I have an IR LED which is switched at a rate of 32.768kHz from an oscillator circuit (relevant portion shown below). I have 10 prototype PCBs. 30% of them work while the others don't. The problem is ...
933 views

Sharing an oscillator between two ICs

I have a microcontroller and an FPGA on the same board. If they're both going to run at the same clock speed, can I just use one oscillator to clock them both? There seems like there is something I ...
2k views

PIC keeps resetting: Am I seeing side-effects from breadboard use?

I'm using PIC18F4680 and am having problems running it form a 40 MHz external clock source or 10 MHz crystal in HSPLL mode. Using 10 MHz crystal in HS mode seems to be fine and 5 MHz crystal in HSPLL ...
239 views

Grokking oscillators

Can someone explain to me / point me to a good explanation of the theory behind an electronic oscillator? The Wikipedia entry explains what, but not how, which is what I need to know. TIA.
546 views

Can a Hartley Oscillator be built using Fixed Inductors?

I've been playing around with fundamental circuits (no professional EE background), and became interested in oscillators. I have been trying to build the Hartley oscillator as described here. The ...
1k views

Push Pull Oscillator

Does anyone know how to build a push/pull oscillator or a similar square wave oscillator?
502 views

Stability (phase margin) analysis in real feedback circuits

So I had a bright idea of using negative feedback to control offset current in my data acquisition circuit. Sure, you could do this in software, but removing the offset at the input stage would ...
433 views

Role of capacitor in this circuit

I have troubles understanding the role of C1 capacitor in the oscillating circuit from the schematic below: My question is: what is the role of C1 in this circuit? Is it to ensure that the circuit ...
301 views

Vacuum tube LED flasher

I am wondering if I can make a vacuum tube oscillator for a LED flasher. The problem is I only have 4 vacuum tubes: 14GT8, 12AU6 and 2 12BA6 tubes. I have a 12 volt DC power supply, 10 volt AC, 20 ...
149 views

Does a clock oscillator require a load?

I want to use this clock oscillator http://www.ecsxtal.com/store/pdf/ecs-2100x.pdf It does not require loading capacitance. However, it says "3.3V operation (optional)", yet on the same page it ...
387 views

How good is my xtal design on my pcb?

I'm designing a board for a school project using eagle. I thought I could get away with using the onboard clock of the PIC18 since it's not doing a whole lot (mostly just LEDs), but one of its tasks ...
194 views

LR oscillators (no capacitor)

How could a frequency be generated using one inductor and no capacitors? The waveform is unimportant. The active component could be transistors, logic gates (including schmitt triggers), or if ...
4k views

Internal or external oscillator

I always use the internal oscillator that pics have as I have never found the need to run anything at higher frequency than 8 MHz (which is the fastest the pics I use tend to be able to go). Are there ...
515 views

Op amp analysis question

I was handed the following circuit in order to determine what it does and what is its operating conditions. The circuit was reverse engineered from an old equipment. I have simulated with NI ...
2k views

High-stability oscillators (non-crystal)

Are there any high-stability oscilators, which are not crystal based, given that temperature is stable down to 0.01 C and voltage down to 0.001V? Will LC-based oscillator be able to show performance ...
404 views

What causes oscillators to sync up with each other?

Messing around with simple Theremin circuits, the variable oscillator would get "stuck" in sync with the reference oscillator, and not move until disturbed significantly (like "snap to grid" in a ...
138 views

Can you identify this crystal oscillator?

I've always used the internal oscillator in my AVR microcontroller projects, but have discovered that I need to use an external oscillator to increase the clock frequency. I have some of these 20MHz ...
230 views

Why use capacitors with crystals?

Whenever I come across crystals used in any of MCU or Processor, whether it be 32.768 kHz responsible for Real Time Clock or 25 MHz crystal required for clocking different interfaces connected with ...
563 views

PIC24 Internal Oscillator and Instruction cycles

I have some relative experience on AVR but just minimum with PICs. In order to start a project I've just wanted to verify that I was able to get the internal oscillator working at the right ...
165 views

Understanding and Changing Transistor Oscillator Circuit

I am using a EAST EFM-290ED Buzzer Alarm. It needs to be oscillated to work. I found a simple one transistor setup that makes it work, but I am not sure if it is working well for this buzzer. ...
323 views

How can I invert a solar-powered oscillator's frequency?

I have a hobby project that's been on the backburner for about 3 years now. It's very simple - just a solar-powered oscillator hooked up to a speaker, that changes frequency in response to the level ...
2k views

Is this a suitable sine wave osc? how would I control the frequency?

Overview- I'm making a bank of analog sine wave oscillators and I'm interested in keeping the design compact. I've started by making a Wien Bridge oscillator. As I'm working from a single power ...
1k views

What is the simplest way to make an oscillating signal?

Imagine you have a black box with 5VDC and ground inputs and you have to create one output that is an oscillating signal. What is the simplest circuit that can do so? Can you create a tank circuit ...
361 views

3 phase computer chip

I have just had a conversation with a friend who studied quantum computing. Sadly I have forgotten most of the conversation as it was far beyond my knowledge threshold. Essentially he was saying was ...
516 views

How to connect 4MHZ crystal oscillator to get 16MHZ

I've 10 4 MHZ crystal oscillators. I need a 16MHZ clock signal. Can I connect multiple 4MHZ oscillators somehow (serial, parallel) to get 16MHZ?
578 views

Why aren't 1Hz crystals used to measure seconds?

According to Wikipedia: Many clocks use a 32.768KHz crystal. Is this because the crystal is smaller than a 1Hz crystal? If 1.0 Hz == 1.0 second. Then, why the need for the division?
542 views

Design for an analogue oscillator that doesn't drift in frequency?

VCOs (Voltage Controlled Oscillators) in analogue music synthesizers are notorious for drifting with temperature. What design solutions are there for an analogue audio VCO that keeps close (as in ...
367 views

Clock Shape Changes with Two O-Scope Probes

I have a Max V CPLD development board which has a 10MHz oscillator onboard. I hooked up CH2 probe to the output pin and then wrote a small VHDL program that output the clock to an external pin. I ...
3k views

Using the ATMega328 with the internal oscillator?

I have a project that I think would be best suited for an ATMega328P. However, in every simple project I've seen, people always hook up a 16MHz external oscillator. From what I can see, it should have ...
139 views

What is the function of the bulb in a Wien bridge oscillator?

In this answer it is said that the bulb in a Wien bridge oscillator is for temperature compensation. Is that true? (I thought it is a kind of AGC to stabilize the output level.)
226 views

What's wrong with this Phase Shift Oscillator?

I am trying to design a phase shift oscillator, using a CE Amplifier. I have a Vc of approximately 6V, gain of approximately 40(>29, as required). I aim for an oscillation frequency of 1.5 kHz. But ...
542 views

Does Fosc refer to the crystal frequency before or after PLL is applied for PIC18 microcontrollers?

If I have a PIC18 microcontroller with an 8MHz crystal and 4xPLL, is Fosc 8MHz or 32MHz?
340 views

Building an oscillator out of discrete gates

I want to buid an ocsillator out of discrete XOR gates, I want to acheive 80MHz. I've tried building one from SN74LVC2G86, but rise/fall times I get is about 25ns. Datasheet does not specify the ...
333 views

Setting the internal oscillator speed on PIC12F1822

I'm trying to get a PIC12F1822 to run at 32 MHz. Here are the relevant bits of code: ...
2k views

Problem with a Relaxation Oscillator (using Op Amp)

I'm studying a relaxation oscillator. This wikipedia circuit shows exactly my circuit with the only difference that I'm using different values for each resistor. I called resistor R the one ...
150 views

Homebrewed phototransistors - unijunction versions

Back in the days, when phototransistors were hard to get (especially in some parts of the world like the communist eastern block), one could brew their own by just filing/sawing off the top of a TO 18 ...
307 views

Synchronise crystal oscillator with external short burst

I am trying to generate a stable 4.43361875 MHz clock (i.e. PAL colourburst) synchronised to the colourburst of a PAL video signal. In a PAL signal the colourburst is provided for only about 8-10 ...
3k views

How to configure the internal oscillator in a PIC16F616?

I want to use the internal oscillator in PIC16F616 in 8 MHz configuration and have the I/O function on RA4 and RA5. I've read ...