Schematics or Circuit Diagrams that aid learning.

FreePCB is a free, open-source PCB editor, released under the GNU General Public License. It was designed to be easy to learn and easy to use, yet capable of professional-quality work.

FreePCB – PCB editor

Some of its features are:

  • 1 to 8 copper layers
  • Board size up to 60 inches by 60 inches
  • Uses English or metric units (i.e. mils or mm) for most functions.
  • Footprint libraries courtesy of Ivex Design International Inc.
  • Footprint Wizard and Footprint Editor for creating or modifying footprints
  • Imports and exports PADS-PCB netlists
  • Exports extended Gerber files (RS274X) and Excellon drill files

Example – Logic Analyzer: This is an open-source logic analyzer called MiniLA contributed by Bob Grieb of the User Forum. The image on right is the Logic Analyzer PCB.

FreePCB - PCB editor

Some Features:

  • Up to 32 channels
  • 128 Kb of memory for each channel
  • Sampling rate up to 100 MHz (timebase in 1-2-5 sequence)
  • Input levels compatible with 3.3V and 5V logic
  • Selectable pretrigger/posttrigger buffer size in 8K step

Amplify uV from Sensors to mV levels for A/D Converters, which in turn may drive a display or connect to a uC means MicroController.

I have my own human interface and memory limitation. I am like a 8086 based nobody’s computer in a Penta-Core 5 Ghz Fiber-Computing World, add a 5 Teral Byte HDD. I am Obsolete, i am Legacy.

Now getting back to Bizness, the inputs from the world we interact are analog, A uV level from a Strain Gauge to measure Weight/Pressure; mV from a K Type Temperature Sensor or mV from LVDT Displacement Transducer to Gauge measure linear displacement. All these Low voltage/current, AC/DC need some signal conditioning and special construction – FOR – Amplification, Attenuation, Noise/Pickup Immunity/Rejection, Linearizion, Isolation and Transmission (long wire/wireless).

Thermocouple Amplifier Standard

This means take a small signal sample in the best possible way. The Sensor/Transducer shape and sensing/converting element/technology is chosen/developed. This low mV/uV is then Amplified/Cleaned and Transmitted.Some steps like Linearization can be done by software not all steps. Now we have a nice 0-10 V or 4-20 mA Signal which any A/D with process enthusiastically. The Digital signal will be eagerly processed by a uC with firmware, without batting a eyelid or like the kids say “look no hands” (then its plaster of paris for a few weeks).

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%,

This indicates like LM3914 in dot-mode. It is a drawing i made made to troubleshoot a gadget, around two decades ago. Strangely it had a echo of a design i had made into a 7107 dpm years before that. Now i am scanning all my drawing and notes, useful or not. Clean or with errors. Many Errors = 1 Blunder. Some projects i made have been expensive Blunders. So see them with a skeptic eye, fix them, try them. Thats all for now.

See the Circuit Full Size – Microohm Meter with LED Analog Bar

Microohm Meter with LED Analog Bar

This has a 9V battery power. The 555 spins and a negative voltage for Opamp is created. This is a Low Offset amp of OP37 of Precision Monolithics, Inc PMI an early innovator. This diff-amp amplifies the uV of a 4 wire resistance measurement.

Now the current pump is the 2N2222 you see above the OP37. The FET and 555 do synchronous rectification. The LM324 is the Indicator and Analog to LED Dot-Bar Converter. The probes are Gold Plated, or use solid gold pins if you have them in plenty.

The only way to improve the reception of FM-signals or particularly of stereo FM-signals under disadvantageous receiving conditions is to amplify the antenna signal. This should be made directly at the antenna, since the loss is increased meter by meter of any cable. In most cases higher line attenuations can be expected than usually calculated. Even receivers with an additional noise figure of zero do not show any improvements of the signal-to-noise ratio becomes too low because of a long transmission line. Therefore it is practically useless to require extremely low noise figures only for the receivers.

To avoid interferences of signals received from stations of other bands it is propitious to amplify the FM-band only. The band amplifier shown in Fig. 1.3 is connected directly to the 60 ohm output of the FM-antenna, i. e. it is placed at the top of the antenna pole. The matching is achieved by the input band-pass connected to the base of transistor BFT12, being a typically linear silicon transistor for broadband amplifiers. The output filter matched accordingly to a 60 ohm coaxial line is connected to the collector. The operating voltage of 15 V can be supplied by the coaxial line.

Fig. 1.3

Antenna-amplifier with BFT 12 for FM-range

Technical data:

  • Power gain Gp = 22 db
  • Noise figure F = 3.5-4.0 db or 2.2-2.5 KT0
  • Input and output reflexion coefficient |r1| and |r0| <= 0.3
  • dim(60db) at Vout = 680 mV
  • dim(50db) at Vout = 1000 mV

Optimum operating point of minimum intermodulation

Ic =~ 80 mA Vce =~ 7-7.5 V
Supply voltage 15 V

Coil data:

Vogt coil former, ordering code: Sp 3.5/16.6-2048C
Core: U17

  • L1 : 5 turns Cu 0.6 mm \o
  • L2 : 3 turns Cu 0.6 mm \o
  • L3 : 3+2 turns Cu 0.6 mm \o

Choke Ch1 = Ch2: 20 turns Cu L 0.3 mm \o, cross section of winding = 4 mm

Credits –

Antenna-amplifier with BFT 12 for FM-range
from Design Examples of Semiconductor Devices – Siemens

This is one IC that is like a E-LEGO, this along with Op-Amps and other components can make many interesting projects. Probably the very first Datasheet and Application Note of 555 t he e-lego.

Signetics made the 555,  On some pins like Control Voltage it responds to analog signals and on Reset and Output the signals are Digital like. The 7555 a CMOS version consumes lower power and oscillates at higher frequencies.

NE555 Applications and Specifications

555 trigger voltage cartoon

This evergreen or perennial chip is the favorite among students and hobbyists who want to learn electronics. Here is an original datasheet from Signetics i found online, it has very nice illustrations which will act as an appetizer for learning this science.

I want students to look into these specs pages as it will make your study more invigorating

555 Timer based Circuits – delabs

Signetics made the 555, This is one IC that is like a E-LEGO, this along with Op-Amps and other components can make…

555 The most Incredible Chip

Create an innovative 555 design today, the 555 should be the heart of the circuit. Here are some pages having 555…

I  was enlightened about this Battery Less wonder. This is a boon for rural areas and an emergency tool which depend only on your will and your tendons. I found this bright flash of information when i was looking for supercap vendors.

Learn about Supercaps, dynamo and White LED

Richard J. Nelson on the LED Forever Flashlight. – The future of low power lighting is in the use of the Light Emitting Diode, LED. Sooner or later you will buy one or more LED lights or lamps. The two primary advantages of an LED light source is it’s efficient light generation (exceeding that of fluorescent lamps) and long life, typically 100,000 hours. That is 50 to 100 times more life than most of the bulbs in your house.

Learn about the Eternal Torchlight

This is a Linear Dynamo LED Torch which uses a SuperCapacitor to store the energy. Easy to repair and maintain if necessary.

It uses no batteries and requires only the single LED included. You can even leave the flashlight unused in your car’s glove box for years and you’ll always get that all-important light when you need it most. Forever Flashlight lll pays for itself quickly by saving you the cost of batteries and bulbs.

Bill Bowden’s Circuits is one of the oldest Web Reference, it was hosted by CompuServe homepages and later moved to his own domain website.

A small collection of electronic circuits for the hobbyist or student. Site includes over 100 circuit diagrams, links to related sites, commercial kits and projects, newsgroups and educational areas.

Hobby Circuits - Bill Bowden

Most of the circuits can be built with common components available from Radio Shack or salvaged from scrap electronic equipment…….

Hobby Circuits – Bill Bowden

Some of the Highlights in this website

  • 32.768 KHz Oscillator Using A Common Watch Crystal
  • 40 LED Bicycle Light (555 Timer – 6 volt)
  • Descrete LED fading circuit using 5 transistors
  • Mechanical Wall Clock Quartz Synchronizer
  • Neodymium Magnet Single Pole Motor
  • Variable Voltage and Current Power Supply
  • Micro Power AM Broadcast Transmitter