EngineeringSlash- The electronic projects,electronic project,electronic schematic,electronic design » Simple circuits http://www.engineeringslash.com Engineering blog- electronic circuits , electronic projects,electronic schematic,electronic design,simple circuit and hobby circuits Tue, 09 Feb 2010 05:03:16 +0000 http://wordpress.org/?v=2.9.2 en hourly 1 1.5 Volt Tracking Transmitter http://www.engineeringslash.com/simple-circuits/1-5-volt-tracking-transmitter.html?nucrss=1 http://www.engineeringslash.com/simple-circuits/1-5-volt-tracking-transmitter.html#comments Sat, 23 Jan 2010 10:55:31 +0000 admin http://www.engineeringslash.com/?p=177

1.5 Volt Tracking Transmitter circuit

The current draw for this tracker is 3.7mA, so the 1.5V button cell will last awhile. What the heck am I suppose to hear you ask? When your circuit is working you should see the LED flash quite fast. Take your FM radio and search for the low-beat ‘humbe-humbe-humbe-etc’ equal to the flash of the LED (probably around the 100Mhz). Found it? If that position is interferering with a radio station you can fine-tune it with the variable capacitor. If you like to have the tracker around the 88Mhz you can do that by spreading the windings from the home-made coil just a bit (1/2 a millimeter or so). Anyways, play with it and learn. It is a nice project. The 12-inch antenna can be anything, it is not really that critical. I used a piece of 22 gauge flexible wire. I haven’t checked the range but will do that shortly.

* For stability, use a NPO types for C2 & C4.

* Resistance tolerance for R1 should be 1 or 2%.

* Frequency range is the usual 87-109Mhz on the FM dial.

* The coil is made from 22 ga ‘hookup’ wire, like the solid Bell phone wire. Leave the insulation on.

* The LED is the ‘High Brightness’ type for maximum illumination.

source electro-tech-online .com

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Presenting 3 FM transmitter circuits .

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]]> http://www.engineeringslash.com/simple-circuits/3-fm-transmitter-circuits.html/feed 0 Lie detector circuit http://www.engineeringslash.com/simple-circuits/lie-detector-circuit.html?nucrss=1 http://www.engineeringslash.com/simple-circuits/lie-detector-circuit.html#comments Sat, 23 Jan 2010 10:46:06 +0000 admin http://www.engineeringslash.com/?p=165

lie detector

Here’s a simple lie detector that can be built in a few minutes, but can be incredibly useful when you want to know if someone is really telling you the truth. It is not as sophisticated as the ones the professionals use, but it works. It works by measuring skin resistance, which goes down when you lie.

Here are the details of the specific parts you will need

Part Total Qty. Description Substitutions

R1 1 33K 1/4W Resistor
R2 1 5K Pot
R3 1 1.5K 1/4W Resistor
C1 1 1uF 16V Electrolytic Capacitor
Q1 1 2N3565 NPN Transistor
M1 1 0-1 mA Analog Meter
MISC 1 Case, Wire, Electrodes (See Nots)

Notes
1. The electrodes can be alligator clips (although they can be painful), electrode pads (like the type they use in the hospital), or just wires and tape.

2. To use the circuit, attach the electrodes to the back of the subjects hand, about 1 inch apart. Then, adjust the meter for a reading of 0. Ask the questions. You know the subject is lying when the meter changes.

http://www.aaroncake.net/circuits/lie.htm


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