Testing a Triac

Testing a Triac

These two testing procedures are for use with a digital multimeter in the Ohm's test-range. Testing procedure was actually designed for testing inside micro-waves (magnetrons), but should be no difference in any other circuit. Test in- or out circuit.

A Triac is an electronic switch or relay. Triacs come in many shapes, sizes, and colors. Check the standard terminal designations in the picture below which shows most of the types of triacs that are commonly used in microwave ovens, along with their standard terminal designations.

Located either externally or fixed within an appliance or equipment, the triac operates when it receives an electronics "gate" signal from the control circuitry. It then switches to its closed or "on" state, thus providing for example, a voltage path to the primary winding of the H.V. transformer in a microwave oven and so activating the cooking controls. Or used in a laboratory water-bath which needs to be kept on a specific temperature. The probe-sensor, which is immersed in the water, keeps track of the temperature and sends a gate signal to the triac to either switch on the heating or cooling elements. Most of these probe sensors only contain one or more diodes of the general 1N4148 or 1N914 types.

more info

source : http://www.sentex.ca/~mec1995/gadgets/triactst.htm

TRIAC Light Controller

TRIAC Light Controller

Description
This project is intended for controlling mains powered disco lighting, although there are many other possible uses for controlling almost any mains appliance. It will control five seperate channels at up to 3 Amp per channel. This could be increased by designing another PCB with wider tracks than the PCB included with this design. I could have used relays to control my lights, but triacs seemed like a more sensible solution as they react quicker and are totally silent as they contain no mechanical parts. The low voltage control side and the mains side are totally isolated, as opto-couplers are used to fire the triacs. I have not included any schematics as this project is very simple, expecially due to the fact I have included a PCB.

more info 

LM4844 datasheet

Stereo 1.2W Audio Sub-System with 3D Enhancement
LM4844 datasheet
Description


The LM4844 is an integrated audio sub-system designed for stereo cell phone applications. Operating on a 3.3V supply, it combines a stereo speaker amplifier delivering 495mW per channel into an 8Ω load and a stereo OCL headphone amplifier delivering 33mW per channel into a 32Ω load.

It integrates the audio amplifiers, volume control, mixer, power management control, and National 3D enhancement all into a single package. In addition, the LM4844 routes and mixes the stereo and mono inputs into 10 distinct output modes. The LM4844 is controlled through an I 2C compatible interface.

Boomer audio power amplifiers are designed specifically to provide high quality output power with a minimal amount of external components.

The LM4844 is available in a very small 2.5mm x 2.9mm 30-bump micro SMD (TL) package.


Features


• Stereo speaker amplifier
• Stereo OCL headphone amplifier
• Independent Left, Right, and Mono volume controls
• National 3D enhancement
• I 2C compatible interface
• Ultra low shutdown current
• Click and Pop Suppression circuit
• 10 distinct output modes

Applications


• Cell Phones
• PDAs
• Portable Gaming Devices
• Internet Appliances
• Portable DVD, CD, AAC, and MP3 Players

download LM4844 datasheet

LM4755 datasheet

Description

The LM4755 is a stereo audio amplifier capable of delivering 11W per channel of continuous average output power to a 4Ω load or 7W per channel into 8Ω using a single 24V supply at 10% THD+N. The internal mute circuit and pre-set gain resistors provide for a very economical design solution.

Output power specifications at both 20V and 24V supplies and low external component count offer high value to consumer electronic manufacturers for stereo TV and compact stereo applications. The LM4755 is specifically designed for single supply operation.
 
Features


• Drives 4Ω and 8Ω loads
• Integrated mute function
• Internal Gain Resistors
• Minimal external components needed
• Single supply operation
• Internal current limiting and thermal protection
• Compact 9-lead TO-220 package
• Wide supply range 9V - 40V
 
 
Key Specification


• Output power at 10% THD with 1kHz into 4Ω at VCC = 24V:  11W (typ)

• Output power at 10% THD with 1kHz into 8Ω at VCC = 24V:  7W (typ)

• Closed loop gain: 34dB (typ)

• PO at 10% THD+N @ 1kHz into 4Ω single-ended TO-263 package at VCC=12V: 2.5W (typ)

• PO at 10% THD+N @ 1kHz into 8Ω bridged TO-263 package at VCC=12V: 5W (typ)
 
Applications


• Stereos TVs
• Compact stereos
• Mini component stereos
download lm4755 datasheet

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3V Sweeping Siren Alarm

A while back I was challenged by a visitor to the website. He needed a very loud sweeping siren type audio sound generator powered by 3v. He tried some of the commercial sirens but they were not very loud when powered by 3v. He also said that those devices demanded much higher current than he wanted to use. I gave this problem some thought and came up with a design below.
The circuit uses a LTC1799 precision frequency generator from Linear Technology. A 74HC14 hex Schmitt trigger from Texas Instruments is also used to perform several other functions. One section is wired as a simple 7Hz square wave oscillator. The triangle waveform across that capacitor generates the low frequency sweeping signal for the siren. Two resistors bias the LTC1799 for a center frequency of about 2KHz. A flyback DC to DC converter circuit, produces a 40v peak signal, which is turned on and off according to the output of the LTC1799.
The output is connected to a quality piezoelectric beeper, which has a resonant frequency of about 2.5KHz. The result is a siren which is quite loud but draws only 40ma from a 3v supply. A piezoelectric device from Kobitone, part number 254-PB515-ROX, (Mouser part number 245-PB516) shown above works well. If you want something much smaller, although not quite as loud, try the Murata PKM17EPP-2002-BO shown above (Digikey part number 490-4688).

Click on Schematic below to view PDF version of this Circuit

                                                                       3v-SweepingSiren