Various diagram: activated

Showing posts with label activated. Show all posts

Saturday, October 4, 2014

IC 555 based on water Activated Alarm

This water activated alarm circuit uses a NE555 timer wired as an astable oscillator and powered by the emitter current of transistor BC109C. In dry conditions, the transistor having no bias current and be completely off. As the probe gets wet, a small current flowing between the base and the emitter and the transistor turns on. A higher current flow in the collector circuit allows the IC NE555 osillator sound.

Probe / contacts may use a nonreactive metal. Contacts gold plated or silver age relay can be used, however, a cheaper alternative is the thread of alternate strips of copper a piece of veroboard. These will eventually oxidize over but as very little current flowing in the base circuit, the higher the impedance caused by oxidation is not important. No base resistor is necessary as the transistor is in emitter follower, current limit is the impedance at the emitter (the oscillator circuit)

Thursday, October 2, 2014

Simple IC 555 Touch Activated Switch Circuit

An LED with a suitable series resistance may be included in the circuit and placed in the centre of the touch plate to indicate when the relay is activated. In cases of severe stray pick-up, the unit should be enclosed in a metal casing that should be grounded.
In the circuit, some special precautions have been taken to avoid interference pick-up, to which TTL ICs are especially prone.
To minimise stray pick-up, the interconnections should be as short as possible.
Capacitor C2 is rather large compared to the conventional value (0.0lp.F) used in this position. This modification has proved quite effective.
The power supply shown provides an appropriate DC voltage to drive a conventional relay.
The value of Rl is best chosen by trail and error, and is a compromise between sensitivity and immunity from stray pick-up, Its value lies in the range l.8M to IOM. Rl may be excluded altogether.
If the unitis situated away from the touch sensor, a shielded wire should be used for the connection.
Tl acts as an inverter and converts a rising edge into a falling edge. Transistor T2 is used to provide sufficient drive capability to drive the relay. The external load is connected across the g relay contacts.
An additional decoupling capacitor ((0.0lp.F) may be added as close as possible to the supply terminals of IC 7493. The prototype was constructed on a conventional bread- board.
The circuit basically comprises a touch activated mono- stable vibrator using an NE555 IC, which activates the ITL s 7493 IC used as a bistable. , .
Another modification is the addition of Cl-Rl parallel combination.
The monostable is touch activated and it provides the triggering input to the bistable. However, the bistable triggers only on the falling edge of the monostable output pulse.
This causes a time delay before the load is actually activated. To avoid this, Tl is introduced.

Wednesday, September 24, 2014

Voice Activated Home Automation

Voice recognition is no longer in infancy, especially since Siri just launched on the new iPhone 4S (although similar technology is available on Android too. This project shows you how to use it to automate your home without spending big bucks.

The core of this project is a VRBot speech recognition module. Next, the project creator used some low-cost wireless light switches (you could also use relays). The VRBot speech recognition module recognizes 32 custom voice commands. Once a command is recognized, a wireless switch is activated via a radio receiver. The setup is simple after you spend some time understanding the wireless communication protocol between the different modules. See the project blog to engineer the whole thing yourself.