SMC ELECTRONICS

Circuits


Our Newest Section. Many more circuits will be added soon. - Enjoy!


Notes: All Circuit files are in PDF format and require Adobe® Acrobat Reader.
Each Circuit file is contained on one "landscape" page and
should be printed-out for ease of use and best clarity.

On this page are some Circuit Schematics which might be
useful to the beginning Electronic Hobbyist or Student.
Most are pretty simple, requiring a few inexpensive parts.
A few of the parts might be a little difficult to obtain new,
but are common enough to be in many hobbyist "junk boxes".
Some of the parts used in some circuits aren't that critical,
meaning that substitutions might be able to be used.

Some of the parts used in these circuits we do indeed have in stock,
however, the circuits are provided as a courtesy to you and not just
as an excuse for us to "drum-up" more business.

All circuits should operate correctly and as intended, however,
please be aware that we cannot guarantee anything. We also
cannot answer any questions or give support to any of these circuits.

A note to Schools and anyone else interested:
Feel free to place these files onto your website if you wish, however,
PLEASE DO NOT DIRECTLY HOTLINK TO ANY OF THESE FILES.
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The following disclaimer must be included to keep the lawyers happy.

Disclaimer: All the circuits here are presented AS-IS.
Surplus Material Components / SMC Electronics assumes no responsibility
to the accuracy, performance, or safety of any circuit.

These circuits and schematics are provided as a courtesy to our
customers and guests. Having good engineering practices and
electronic construction skills are the responsibility of anyone
attempting to build or operate any of these circuits.

Some circuits require the connection of Household (120 VAC) current.
This voltage level can cause serious harm or death if improperly used.
Such circuits should not be constructed or operated by anyone not familar
with safety practices regarding high voltages.

Children should always be supervised by an adult who has a sufficient
understanding of safety practices.

Finally: If you have trouble figuring out how to operate a light switch
or a doorknob, maybe you should take up gardening as a hobby instead.



1 KHz TONE GENERATOR
Only 9 parts are needed to build this handy tone generator.
Useful as a microphone tester or just to make some noise.
Uses the classic (and cheap) 555 timer IC.

(PDF File size: 229K)



2-WAY LED FLASHER
Simple circuit alternately flashes two LEDs.
Would make a fine "Crossing Light" for a model railroad.

(PDF File size: 213K)





2.5 VDC REFERENCE
With just a few parts, this Voltage Reference is perfect for Voltmeter
and Oscilloscope Calibration or for any use that requires a stable,
precision Voltage Reference. Operates on a 9 Volt battery.

(PDF File size: 208K)



5 VOLT REGULATED POWER SUPPLY
Only 8 parts are needed to build this versatile power supply.
Uses the classic (and cheap) 3-pin 7805 IC regulator.

(PDF File size: 328K)



7-SEGMENT LED DISPLAY COUNTER
Two common ICs and seven resistors are all that is needed for
this circuit. Circuit causes LED display to indicate from 0 to 9.
For use with 7-segment common-anode LED displays.

(PDF File size: 229K)



12V LATCHING RELAY CIRCUIT
Any standard DPDT relay can be converted to a
SPDT Latching Relay. No real parts are needed
except for maybe a pushbutton switch. This circuit
would make a good addition to any alarm circuit.

(PDF File size: 215K)



12 VOLT REGULATED POWER SUPPLY
Only 8 parts are needed to build this versatile power supply.
Uses the classic (and cheap) 3-pin 7812 IC regulator.

(PDF File size: 313K)



100 KHz FREQUENCY STANDARD
Small crystal-controlled circuit useful as a frequency standard
or for use as a marker generator when used with an older
analog-tuned shortwave or HAM radio receiver.

(PDF File size: 246K)



AUTOMOTIVE FUSE TESTER
Two LEDs and one resistor are all that is needed
to test any fuse "in-circuit".

(PDF File size: 215K)



AUTOMOTIVE LED FLASHER
Two transistor circuit blinks a red LED once per second.
Perfect for use as a "Fake Alarm-On" indicator.

(PDF File size: 218K)



COMPOSITE VIDEO DETECTION CIRCUIT
This circuit can detect standard composite video from a VCR,
Video Camera, or other similar device. When video is detected,
circuit will close a relay.

(PDF File size: 240K)



CONTINUITY TESTER
The most basic (and important) first piece of test equipment
that a beginner should learn how to use. A Continuity Tester
determines whether two points are electrically connected.

Use to test wires, fuses, switches, lamps, relays, connectors,
almost any electrical item.

(PDF File size: 180K)

A complete wired version of this circuit is available here:



ELECTRET CONDENSER MICROPHONE DRIVER
Simple Electret Condenser Microphone Driver/Preamplifier.
Circuit allows the use of Electret Condenser Microphone
elements with tape recorders and other audio equipment.
Only 7 parts are needed.

(PDF File size: 210K)



IR LED ILLUMINATOR
Simple infrared illumination circuit allows most black and white
CCD/CMOS security cameras and many digital cameras to
"see in the dark". Also perfect with use with IR nightscopes.

(PDF File size: 173K)



LM3909 LED FLASHER
Only 3 parts and a battery are needed to build this handy little LED blinker.
Uses the somewhat hard-to-find LM3909 IC.

(PDF File size: 152K)



MORSE CODE PRACTICE OSCILLATOR
A handful of inexpensive parts are all that is needed to build this
Morse Code Practice Oscillator. Learning and using Morse Code,
especially if you are a Ham Radio operator, might come in handy
someday. In times of an emergency, it might be the only form of
communications that can get through. Again, this circuit uses the
classic (and cheap) 555 timer IC.

(PDF File size: 221K)



OCTOPUS OSCILLOSCOPE COMPONENT TESTER
This poor man's curve tracer circuit has been around for about 80 years.
(Yes, your grandfather or great grandfather might have actually known
more than you about electronics.) The Octopus Circuit basically uses
just a transformer and three resistors, along with just about any oscilloscope.
The circuit will produce a "signature" waveform on the oscilloscope to aid
in the testing and analysis of shorts, opens, and leakage in just about any
electronic component including resistors, capacitors, inductors, diodes,
and transistors.

(PDF File size: 290K)



SEQUENTIAL LED FLASHER
Simple circuit sequentially flashes ten LEDs in a row.
Perect for making a moving "Marquee Sign".

(PDF File size: 156K)





TELEPHONE LINE TESTER
Simple circuit will test whether a telephone line is
"live" or not and with correct wiring polarity.

(PDF File size: 125K)

A complete wired version of this circuit is available here:



TTL CLOCK CRYSTAL OSCILLATOR FREQUENCY STANDARD
The poor-Man's Precision Frequency Standard.
Use almost any TTL Clock Crystal Oscillator
and two capacitors. Output of circuit is great
for quickly testing the readings of Frequency
Counters or the displays of Oscilloscopes.

(PDF File size: 203K)



TTL LOGIC PROBE
Four common parts are all that is needed for constructing
this simple, inexpensive TTL Logic Probe.

(PDF File size: 358K)



TTL SWITCH DEBOUNCER
A few parts are all that is needed for constructing this circuit.
Circuit produces one "clean" TTL compatible pulse with
each depressing of a pushbutton switch.

(PDF File size: 272K)



VARIABLE REGULATED POWER SUPPLY
Only a few parts are needed to build this quality variable power supply.
Power supply outputs 1.2 - 30VDC at 1.5A.
Uses the classic (and cheap) 3-pin LM317 IC regulator.

(PDF File size: 158K)




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