Touch Sensor Switch Circuit with 555 timer -  This is a very simple touch sensor switch that is build with the 555 timer IC. You just need to touch the metal plate and the relay gets energised and is kept in this state for about 100 seconds, then is released. This kind of sensor switch is suitable for making touch operated bells, buzzers of small toys which operate for a. . .  [Circuit posted by Popescu Marian]

Touch Switch -  The Touch Switch circuit will detect stray voltages produced by mains voltages and electrostatic build-up in a room. In the first circuit, pin 2 must see a LOW for the circuit to activate. If sufficient static voltage is detected by the plate, the chip will change state. If not, you will need to touch the plate and the 0v rail. . .  [designer's name not found on the website]

Touch-Free Timer Switch -  The simple circuit presented here can be operated by moving your hand in front of it. This is achieved by detecting the infrared light reflected by your hand onto a receiver device. . . .  [© EFY Enterprises Pvt. Ltd. All rights reserved.]

Toy Organ -  This circuit produces a tone according to the button being pressed. Only 1 button can be pressed at a time, that's why it is called a monophonic organ. You can change the 1k resistors to produce a more-accurate scale. . . .  [designer's name not found on the website]

Traffic Light -  This project operates red, amber and green LEDs in the correct sequence for a single UK traffic light. The time taken for the complete red, red & amber, green, amber sequence can be varied from about 7s to about 2½ minutes. A 4017 counter is used to produce the traffic light sequence and this project could be adapted. . .  [John Hewes]

Traffic Lights -  Here's a clever circuit using two 555's to produce a set of traffic lights for a model layout. The animation shows the lighting sequence and this follows the Australian-standard. The red LED has an equal on-off period and when it is off, the first 555 delivers power to the second 555. . .  [No designer name given]

Traffic Lights-4 Way -  This circuit produces traffic lights for a "4-way" intersection. The seemingly complex  wiring to illuminate the lights is shown to be very simple, in this diagram. . . .  [No designer name given]

Transcendent Frequency Counter -  This is a top quality project designed to obtain maximum performance. The hardware and software has been pushed to reach the frontier of technology. The transcendent is not only a frequency counter, it is a corner stone in your successfully constructions. . . .  [can't find owner's name on website]

Transistor Tester -  The 555 operates at 2Hz. Output pin 3 drives the circuit with a positive then zero voltage. The other end of the circuit is connected to a voltage divider with the mid-point at approx 4. 5v. . . .  [No designer name given]

Transition Counter Gauges Thermal Stability -  01/04/96 EDN Design Idea   The transition counter of Figure 1 is an easy way to determine if the temperature in a heater is stable. The stable state maximizes the transitions. This circuit works like a digital filter with controlled frequencies and is sim. . .  [by Jose Luis Arce, Tecnosuma Havana, Cuba]

Triggering and Timing Helpers for Monostable Timers -  Uses the LM555 timer or its cousins with other letter prefixes. There can be minor differences between 555 timer IC's from different manufacturers but they all should be useable for any circuit. Designed for Model Trains. . . .  [from Rob Paisley's Model Train web site]

Trimming the Internal Clock on a KX8 Microcontroller -  Example algorithms for manually or automatically tuning the oscillator on the internal clock generator of the popular MC68HC908KX8 microcontroller. Also includes batch test results and a video. . . .  [Robot Room website]

TV Remote Control Jammer -  This circuit confuses the infra-red receiver in a TV. It produces a constant signal that interferes with the signal from a remote control and prevents the TV detecting a channel-change or any other command. This allows you to watch your own program without anyone changing the channel. . .  [No designer name given]

Two CMOS Based 24-Hour Timers -  A pair of multi-range timers offering periods of up to 24 hours and beyond. Both are essentially the same. The main difference is, that when the time runs out, Version 1 energizes the relay and Version 2 de-energizes it. The first uses less power while the timer is running; and the second uses less power after the timer stops. Pick the one that best suits your application. . . .  [Circuit design by Ron J.]

Two nixie display clock -  My clock building habit is apparently as bad as ever. This time, it was inspired by a stash of Burroughs B5092s, so I needed to vertically align it. Also, since I wanted to make it as small as possible, I wanted to keep nearly everything surface mount, so I abandoned the idea of using 74141s in favor of standard BCD to decimal converters plus some external drive transistors. No need to multiplex since I'm only using two tubes, so this design is actually pretty straightforward. . . .  [© 2007 by Riad S. Wah[by]

Two Tone Generator -  This two-tone generator includes 3 ICs NE555 Astable Multivibrators. You can vary the duration of each tone by changing the 10k resistor or 100MF capacitor at IC1 or changing resistors and capacitors at IC1/2 for higher or lower tone. . . .  [Designed by Andrew R. Morris]

Two Tone Generator -  This two-tone generator includes 3 ICs NE555 Astable Multivibrators. You can vary the duration of each tone by changing the 10k resistor or 100MF capacitor at IC1 or changing resistors and capacitors at IC1/2 for higher or lower tone. . . .  [Circuit Designed by Andrew R. Morris]

Two Transistor Atomic Frequency Standard -  Pretty ambitious title, wouldn't you say? Well, follow the reasoning: If you lower the voltage on the two-transistor flasher to 1. 5 volts, the loop gain drops too low for sustained flashing. (See the circuit below. ) But, the circuit is highly regenerative and only needs a very tiny push to get it going. By adding a short wire, only a few inches, to the PNP base, the circuit will be triggered into oscillation by the AC electric field from the electrical power (50 or 60 Hz in most places) . . .  [Charles Wenzel, designer]

Two-tone doorbell using 555 timer -  No circuit description, schematic only. . .  [CdS Electronic's website]

Two-Transistor Low Power Oscillators -  This page has two unusual two-transistor oscillators. I set the component values for a low frequency application. Both circuits draw only about 1 micro amp of current . . . [Hobby Circuit designed by Dave Johnson P.E.,  12/14/02]

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