Archive for the ‘Electronics Projects’ Category
FM Transmitter
Saturday, February 17th, 2007Here is the schematic, PC board pattern, and parts placement for a low powered FM transmitter. The range of the transmitter when running at 9V is about 300 feet. Running it from 12V increases the range to about 400 feet. This transmitter should not be used as a room or telephone bug.
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Schematic
PC board layout and parts placement
Parts:
Part Total Qty. Description Substitutions
C1 1 0.001uf Disc CapacitorÂ
C2 1 5.6pf Disc CapacitorÂ
C3,C4 2 10uf Electrolytic CapacitorÂ
C5 1 3-18pf Adjustable CapÂ
R1 1 270 Ohm 1/8W Resistor 270 Ohm 1/4W Resistor
R2,R5,R6 3 4.7k 1/8W Resistor 4.7K 1/4W Resistor
R3 1 10k 1/8W Resistor 10K 1/4W Resistor
R4 1 100k 1/8W Resistor 100K 1/4W Resistor
Q1, Q2 2 2N2222A NPN Transistor 2N3904, NTE123A
L1, L2 2 5 Turn Air Core CoilÂ
MIC 1 Electret MicrophoneÂ
MISC 1 9V Battery Snap, PC Board, Wire For Antenna
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 Notes:1. L1 and L2 are 5 turns of 28 AWG enamel coated magnet wire wound with a inside diameter of about 4mm. The inside of a ballpoint pen works well (the plastic tube that holds the ink). Remove the form after winding then install the coil on the circuit board, being careful not to bend it. 2. C5 is used for tuning. This transmitter operates on the normal broadcast frequencies (88-108MHz). 3. Q1 and Q2 can also be 2N3904 or something similar. 4. You can use 1/4 W resistors mounted vertically instead of 1/8 W resistors. 5. You may want to bypass the battery with a .01uf capacitor. 6. An antenna may not be required for operation. |
TWO TONE TRAIN HORN.
Monday, October 30th, 2006BEST CIRCUITS OF THE WEEK
Monday, October 30th, 2006Â 
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