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24 Jul 2014

photo

Clap switch/Sound-activated switch designed around op-amp, flip-flop and popular 555 IC. Switch avoids false triggering by using 2-clap sound. Clapping sound is received by a microphone, the microphone changes the sound wave to electrical wave which is further amplified by op-amp.

555 timer IC acts as mono-stable multi-vibrator then flip-flop changes the state of output relay on every two-clap sound. This can be used to turn ON/OFF lights and fans. Circuit activates upon two-clap sound and stays activated until another sound triggers the circuit.

Sound Activated Switch - [Link]

18 Jun 2014

This Photodiode based Alarm can be used to give a warning alarm when someone passes through a protected area. The circuit is kept standby through a laser beam or IR beam focused on to the Photodiode. When the beam path breaks, alarm will be triggered. The circuit uses a PN Photodiode in the reverse bias mode to detect light intensity. In the presence of Laser / IR rays, the Photodiode conducts and provides base bias to T1.

The NPN transistor T1 conducts and takes the reset pin 4 of IC1 to ground potential. IC1 is wired as an Astable oscillator using the components R3, VR1 and C3. The Astable operates only when its reset pin becomes high. When the Laser / IR beam breaks, current through the Photodiode ceases and T1 turns off. The collector voltage of T1 then goes high and enables IC1. The output pulses from IC1 drives the speaker and alarm tone will be generated.

A simple IR transmitter circuit is given which uses Continuous IR rays. The transmitter can emit IR rays up to 5 meters if the IR LEDs are enclosed in black tubes.

555 Photodiode alarm - [Link]

31 May 2014

This Photodiode based Alarm can be used to give a warning alarm when someone passes through a protected area. The circuit is kept standby through a laser beam or IR beam focused on to the Photodiode. When the beam path breaks, alarm will be triggered. The circuit uses a PN Photodiode in the reverse bias mode to detect light intensity. In the presence of Laser / IR rays, the Photodiode conducts and provides base bias to T1.

The NPN transistor T1 conducts and takes the reset pin 4 of IC1 to ground potential. IC1 is wired as an Astable oscillator using the components R3, VR1 and C3. The Astable operates only when its reset pin becomes high. When the Laser / IR beam breaks, current through the Photodiode ceases and T1 turns off. The collector voltage of T1 then goes high and enables IC1. The output pulses from IC1 drives the speaker and alarm tone will be generated.

A simple IR transmitter circuit is given which uses Continuous IR rays. The transmitter can emit IR rays up to 5 meters if the IR LEDs are enclosed in black tubes.

555 Photodiode alarm - [Link]

12 May 2014

Photoswitch_Teardown_7809-500x375

Alan Parekh @ hackedgadgets.com bought a photo-switch on ebay and takes a look inside.  He writes:

I spotted this photoswitch on eBay and had to take a look at the guts (search photoswitch if the link doesn’t work since eBay links go stale after a short time). I now see that the same unit is sold in multiple variations which are 24V and 220V. Not sure I would feel safe with 220 on this thing though. I am curious if the 10 ohm resistor is the only difference between the versions. If someone has one of the other versions leave a comment to let us know what the difference is. These are selling for $3.39 which included free shipping from China to Canada! Hard to believe how tilted the scales are here, I wouldn’t be able to ship this within my city for $3.39. The unit is powered from 12 volts AC or DC, it also switches the same power to the third output wire when activated. The circuit is using a 555 for operation. When the photocell goes from light to complete darkness the relay activates in 3 or 4 seconds. You can view full resolution images here.

eBay Photoswitch Teardown - [Link]


8 Apr 2014

Build this homemade “one-size-fits-most” speed controller for use with your hobby projects. It’s small, it’s flexible, and it’s built with off-the-shelf components around the venerable 555 timer IC.

Dial-a-Speed Motor Controller - [Link]

28 Jan 2014

valentine_front

This is a heart-shaped LED chaser would be a nice gift for Valentine’s Day. Circuit is very simple and uses the 555 timer IC (configured as astable multivibrator) and CD4017B decade counter.

The object of your desire will not be able to resist a heart-shaped LED chaser, lovingly hand-crafted on perfboard with a CD4017B decade counter and 555 astable. But you probably can’t go wrong with flowers and chocolates as well. Just to be on the safe side.

[via]

Heart-shaped LED chaser for Valentine’s Day - [Link]

 

17 Jan 2014

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Nick Leijenhorst build a 555 PWM circuit to dim his room LED lighting. He writes:

I wanted to dim my room LED lighting with a potentiometer, and decided on creating a solution from scratch to make it more fun and educative. I decided to go with the fairly well-known 555 PWM circuit. To decrease size and for learning purposes I decided on using surface-mount components for the first time. The reason I wanted to make this 555 PWM circuit is actually just to see if I could solder SMD components on home-etched PCB’s, and to see how hard it actually is.

[via]

Surface-mount 555 PWM circuit - [Link]

14 Dec 2013

Dave celebrates the classic 555 timer IC by building the Evil Mad Scientist “three fives” discrete timer kit. Some scope measurements and an explanation of the internal 555 timer circuitry follow.

EEVblog #555 – 555 Timer Kit - [Link]

15 Jun 2013

vfdfilamentdriver-600x450

Kerry Wong documented his VFD filament driver built:

I recently salvaged a vacuum fluorescent display (VFD) from a piece of old test gear. The VFD is a 13 digit 7-segment multiplexed display and I thought it would look great in a custom digital clock or something similar. While it has the model number FUTABA 13-MT-54NA, I could not find any information on the internet specifically for this model. Of course, before I could put this vacuum fluorescent display to use in my final project, I needed to first build a driver circuit to drive this display.

[via]

VFD filament driver using 555 - [Link]

4 Jun 2013

555-timer-triggers-phase-control-circuit-figure-1

JN Lygouras, University of Thrace writes:

The control circuit in Figure 1a allows you to manually adjust the power delivered to a load. By changing the setting of potentiometer R3, you change the phase angle at which the thyristor (Q3) fires (Figure 1b), thereby altering the load current’s duty cycle. The adjustment range is about 0 to 180°. Q3’s off time is linear with R3, but of course the resulting load power is not linear with R3.

555 timer triggers phase-control circuit - [Link]



 
 
 

 

 

 

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