G-switch timer – Vern Knowles

The timer is built using four small inexpensive CMOS integrated circuits. This allows it to run on just 3V from two small AAA batteries. U1 is a 74HC688 8-bit equality comparator. It compares the switch settings to the counter output and will set pin U1-19 low when they match. The actual counter is U2. It is a 74HC4060 14-stage binary ripple counter with built-in oscillator.

The G-switch itself uses a cantilevered metal bar that pivots down as the rocket accelerates upward. The metal bar actuates a small micro-switch that triggers a digital counter to begin the timing sequence. The timer is designed so that it will not start unless the micro-switch has been activated for a duration of at least 0.5 seconds.

G-switch timer - Vern Knowles

G-switch timer – Vern Knowles – The timer was built using a small prototyping circuit board and point-to-point wiring.

U3 is a 74HC74 D-type flip-flop that is used as part of the triggering logic. U3-12 will be low when the counter matches the switch settings. Consequently, on the next oscillator clock edge from U2-9 the flip-flop output at U3-9 will go low. This is the event that activates the 2N4403 transistor that fires the flash bulb.

Flashing Mains Neon Lamp

Here is a Neon Flasher circuit (untested) for a user request at Circuits FAQ. This can be built into a switchboard or a gadget for indicating Live Power.

D1-C1 form a simple half-wave rectifier, The Cap charges to peak voltage and can store charge for a long time if there is no bleeder. So while building it take extra care. This forms a DC supply across C1. C1 is a Plastic High-voltage cap, IN4007 has a 1KV rating, so it is ok for 230V rectifier.

R1 Charges C2 and when C2 reaches 60-80V depending on Neon, the neon breaksdown. C2 Discharges, Neon Recovers, The C2 starts charging again and so on and on. It Oscillates, probably in a Ramp Waveform. But do not use your Scope on this, you will regret it a lot. This is a live circuit and needs a special probe.

“Oh, i will put the probe it in 10M mode” will not do. The ground clip of the probe goes to Electrical Earth which is ‘connected’ to Neutral in the mains wiring. So you put the earth crocodile clip on the live point. There will be flashes and fireworks. So you need to isolate both terminals of scope. Please use your costly equipment with great care.

For the 1 Meg use two 470K in Series for 230V AC, that is safer. The circuit is live, so take precautions. The 0.47 Micro Farad can be increased if you want a slow flash. If the Mains 50/60 Hz Flicker is too much, the 1 uF can be made 2 uF, or use 4 – 1N4007 as a bridge rectifier.

From Schematics of delabs

User Feedback –

R1 of 4.7M and C2 of 0.47uF Works well at 230V AC. Try your own Combination. Less than 1M may damage Neon.

VU Meter Circuits and Projects

Here is a collection of web pages of VU Meter projects that helps a newbie getting into the Electronics DIY Hobby Land.

VU Meter Circuits and Projects

A Hobby now in your School days or College can help you build a strong profession later. It is Edutainment that will make productive use of your spare time. Friends can do it as a group, during holidays. Parents should encourage healthy hobbies, as the children will grow in a positive and creative atmosphere.

Stereo led level meter – This is it. It’s a STEREO LED LEVEL METER. It’s the cheapest and best bar graph display available and best of all, it uses readily available components.

VU-meter by Archy – Then it hit me. A VU meter, big, beautiful, professional! From that moment started my thoughts flowing. Those VU-meter ICs that are sold in every electronics shop?

LM3914 dot-bar display driver – The LM3914 is a monolithic integrated circuit that senses analog voltage levels and drives 10 LEDs, providing a linear analog display.

Knight Rider Display Project – This project started out as a VU meter. I reused parts and pieces to improve the VU meter and give it additional functionality. It is amazing how much time it takes to create a small thing like this.

RASON Projects Page

Designing Bipolar Transistor Audio PreAmps, Designing JFET Transistor Audio PreAmps, Designing Op Amp IC Audio PreAmps, Switching Regulator Basics, Using Transistors As Switches.

RASON Projects Page – Amateur Radio

  • 10 Amp, 13.8 Volt Power Supply
  • 12 Volt Gel Cell Charger
  • Thermal Fan Controller
  • Transistor Audio Amplifiers
  • 12 Volt Gel Cell Charger
  • Switching Regulator Basics


A Potpourri of Audio Amplifiers  By N1HFX

“I intentionally avoided the use of IC amplifiers to provide a real learning experience for audio amplifier design. Although many IC amplifiers provide excellent performance at low cost, we need to learn the basics first. I will address IC audio amplifiers in a future article.”

The Radio Amateur Society of Norwich
P.O. Box 329 – Norwich, Connecticut 06360

Elliott Sound Products – The Audio Pages

There is a very wide range of power amplifiers, preamps, guitar/ bass amplifiers, studio equipment, effects, and other projects to build, including loudspeakers, subwoofers, and many others

Elliott Sound Products – The Audio Pages

Elliott Sound Products - The Audio Pages

  • Projects – Complete listing of ESP’s free project and design articles
  • Articles – Informative articles about audio, building projects, and electronics in general
  • Buy PCBs for ESP Projects – boards supplied have very comprehensive documentation.

ESP Resource of Rod Elliott –  The above pages has many useful ideas and practical tips – delabs

It is by Hobby and DIY – Do it Yourself, Education Starts even without books. Then you need to read to enhance your abilities to Design your own.

In order to compensate or enhance your education, you need to work at a small shop as an apprentice even as a student, not for the sake of project work alone. An Evening job at a factory or a home mini workshop-lab is very essential for obtaining the skills – Solderman 1702

Experiments with the LM2575

The standard buck regulator circuit delivers a +5V output. This is a rather straightforward circuit and will operate with a wide spread of component values. Optimal values should be selected however to get minimal ripple, minimal noise to the power source, maximum efficiency etc. Note that the quiesent current is about 10 to 14mA.

Experiments with the LM2575

Here is a nice way of using this regulator, this can be used for CMOS opamps as you have a -5V too. That means a portable instrument may find this design useful.

The TI Datasheet Layout Guidelines

LM2575 Switching Regulator
LM2575 – Step-Down Adjustable Voltage Switching Regulator with Output Enable

 The Spirit of Hacking and Fixing, Giving back Life to Old Instruments.

Fluke 8050A LCD display replaced with LED seven-segment

“Recently I was able to cheaply buy a second hand Fluke 8050A made in the early eighties. It is a nice 4.5 desktop digit meter, but a typical problem seems to be that the LCD wears out and goes black. Replacement LCD displays are hard to find, not cheap and probably lead to similar problems in due time.”

Low Cost AM FM Stereo Receiver

This was a National Semiconductor Application Note, now TI. – Low Cost IC Stereo Receiver.

AN-147 Low Cost IC Stereo Receiver

Some Highlights

The LM3089 FM IF System does all the major functions necessary for FM processing, including a three stage amplifier/limiter and balanced product detector, as well as an audio preamplifier.

FM stereo demodulation is accomplished by the use of the LM1800 phase locked loop, thereby eliminating the need for external coils.

The AM function of the receiver is done completely with the LM3820 AM radio system. While designed for 3 section tuned superheterodyne application.

The LM382 dual preamplifier was selected for its minimum parts count and low noise capability.

Panel meters are employed in the FM system for both signal strength and center tuning, allowing for easy and accurate tuning. A directly driven LED offers immediate indication of FM stereo reception.

Low Cost AM FM Stereo Receiver

A single transistor tone control circuit was designed as the optimum cost/performance trade-off. The transistor is configured in a shunt-shunt feedback design, allowing gain variations between input functions.

The stereo power section, consisting of the LM378 dual audio amplifier, delivers 3W/channel with total harmonic distortion (THD) less than 1% and 4W/channel with THD less than 10%,