555

Posted on Feb 5, 2014

I learned that you could do PWM with the 555 chip. So I tested this idea. I will not attempt to explain the workings of the 555 chip because I found the page by Tony van Roon to be an excellent introduction to the 555 chip. Tony`s page discusses a slightly different setup that what I tested. The key difference is an additional diode.

Click here to download the full size of the above Circuit.

I added this diode so that one resistor is dedicated to the charging the capacitor and the other resistor is dedicated to the discharge process. I added a potentiometer to vary the charging and discharging resistor. Here is my schematic: This circuit uses Pulse Width Modulation to change the LED from dim to bright as the potentiometer is turned. Here is a simulation that closely resembles my circuit. I modified the capacitor so the simulation would run slower. The graphs show the capacitor and the voltage following the LED. When the 555 chip sends a pulse to the transistor, the transistor will allow current to pass from the collector to the emitter. The LED will light and the voltage at the junction of the LED and transistor will drop. When no pulse is sent, the transistor prevents the flow of current through the LED. In this case, we will see a high voltage at the junction of the LED and transistor. In this photo, we see a few more pulses at the bottom. This indicates the transistor is allowing current to pass through the diode in longer durations. The diode appears a little brighter in this photo. In this case, the 555 chip is sending long pulses to the transistor. The transistor is allowing current to pass most of the time. Thus, the voltage at the junction of the transistor and LED is low (most of the time). This results in the near solid line.

Visit page

Leave Comment

characters left:

Related Circuits

Color sensor

Color sensor. Colour sensor is an interesting project for hobbyists. The cir- cuit can sense eight colours, i.e. blue, green and red (primary colours); magenta, yellow.

Dew sensor

Dew sensor. Dew (condensed moisture) ad- versely affects the normal per- formance of sensitive electronic devices. A low-cost circuit described here can be used to.

Audio Visual Ringer

Audio Visual Ringer. Many a times one needs an extra telephone ringer in an ad-joining room to know if there is an incoming call. For example, if the telephone is installed in.

Multipurpose Circuit for telephone

Multipurpose Circuit for telephone. This add-on device for telephones can be connected in parallel to the telephone instrument. The circuit provides audio-visual indication of on-hook,.

Off line Telephone tester

Off line Telephone tester. Here is a circuit of an off-line telephone tester which does not require any telephone line for testing a telephone instrument. The circuit is so simple that.

Telephone Headgear

Telephone Headgear. Acompact, inexpensive and low component count telecom head- set can be constructed using two readily available transistors and a few other electronic.

Telephone line based audio muting and light on circuit

Telephone line based audio muting and light on circuit. Very often when enjoying music or watching TV at high audio level, we may not be able to hear a telephone ring and thus miss an important...

Telephone Ringer using 556 dual timers

Telephone Ringer using 556 dual timers. Using modulated rectangular waves of different time periods, The circuit presented here produces ringing tones similar to those produced by a telephone. The.

New Circuits

Zero consumption Anti-theft High power Code Switch for E-Bike Batteries

This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
Ultrasonic distance finder circuit

The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Simple Metal detector circuit with CD4030

Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Fully automatic watering circuit for flower pots

Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
Simple deep searching metal detector circuit

The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
Sub-Harmonic Bass Converter for Electric Guitars

The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
Echo Depth Sounding Sonar for Boats

In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
100W HiFi Audio Amplifier Circuit

This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
Plant-Pot Water Level Indicator Circuit

A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....

Create NOW your QR MENU for your Restaurant / Hotel / Bar / Caffe,

Comprehensive ordering/paying features. fully personalized to suit your Business.

Update Anytime! Easy and Simple!

Popular Circuits

Metal detector with 4030 CMOS

This battery-powered metal detector uses four exclusive-OR gates contained in the 4030 CMOS...

Motorola SN54 Demultiplexer Logic Diagram and Datasheet

Motorola SN54/74LS138 known to be 1-of-8 decoder or demultiplexer which is designed for high...

how to build bicycle back safety light

This circuit has been designed to provide a clearly visible light, formed by 13 high efficiency...

battery monitor circuit

Here is a battery monitor circuit which can be used to monitor the voltage of 12V lead acid...

250mw 16 db vhf amplifier

This is an 250mW RF power amplifier project. This circuit is designed to amplify the output of...

Pulse Charger for reviving tired Lead Acid batteriess

Before you begin a project like this remember: mains voltage is dangerous so if you are not 100%...

Stepper Motor Controller

Stepper motors are useful for relatively low-speed, intermediate-torque drive and positioning...

Simple Easy Parametric and Graphic EQs Plus Peaks and Notches

Everyone is familiar with the sound of a wah pedal. This is a resonant peak in the signal that...

light gate with counter

The circuit described here counts the number of times that an infrared beam is interrupted. It...

The Audionics CC-2 Amplifier

Although the Audionics CC-2 is named after Cliff Moulton (Audionics` chief engineer) and Charles...