Wiring Schematic Diagram

1.5V Battery operated FM Transmitter

This accomplishing is acclimatized to rebroadcast the achievement of a CD player, television receiver, or radio receiver. I use it so that I can move about the abode and accept to my admired programs after advancing others. Within and the house, I acquisition that I can get 10 to 20 meters abroad from the transmitter with the baby abridged FM receiver I backpack in my shirt pocket. Your breadth may vary.

The transmitter as congenital and pictured beneath (the transmitter is in the balloon of hot cook cement on the end of the array holder) does not accept an on-off switch. I put a 1.5 AA corpuscle that was run bottomward too far to run my CD amateur in this transmitter and it ran for over a ages afore I replaced it. The one in the transmitter at this moment has been active it continuously for over three months. Current draw is alone about a milliamp with a new array (assuming you don't accept a super-high beta transistor in which case the abstract absolute is about 2.5 ma). An on-off swich is not necessary, admitting it may amuse an affecting need.

Tips to get it working: Wind the braid on a 4 or 5 mm bore Philips brand screwdriver or agnate anatomy again blooper it off. I acclimated some vinyl cloistral #24 amalgamation wire as able-bodied as #30 enameled wire. In both cases, I played with the breadth of the braid to tune the transmitter to a asleep atom on the FM band. The braid is captivated in abode with hot cook glue. If you don't accept a spectrum analyzer or abundance meter, use a good-quality FM receiver to accomplish abiding its acquainted area you anticipate it is. While adjusting the coil, accumulate in apperception that all superheterodyne receivers accept images. If you acquisition that two or added adjustments accomplish the transmitter appearance up on the aforementioned atom on the receiver, it ability be all-important to booty a abbreviate airing and acquisition out which acclimation drops out aboriginal -this would be the image, because the receiver's advanced end (if it has a acquainted advanced end) will abate its acuteness to the image.

Many kinds of transistors will assignment accomplished in this application. After all, its alone an oscillator (frequency accentuation is acquired my modulating the base-collector voltage, thereby modulating the abyss of the burning band of the reverse-biased base-collector junction, which after-effects in a change in capacitance at the collector, which after-effects in a change the beating abundance of the beneficiary circuit.). I acclimated an 2N4401 because I accept a lot of them. I like 2N3904 and MPSH34 for this too.

R1= 1Kohms    D1 = 1N4001                 T1 = 15V/5A Transformer
R2= 1.2Kohms  D2 = 6.8V 0.5W zener        LD1= Green LED
R3= 470 ohms  TR1= 4.7Kohms trimmer       LD2= Red LED
R4= 470 ohms  Q1 = BTY79/similar 6A SCR   M1 = 5A DC Ampere meter
R5= 10K ohms  Q2 = C106D SCR              S1 = On-Off Switch
C1= 10uF/25V  GR1= 6A Bridge Rectifier    F  = 5A Fuse 

Car Battery Voltage Indicator Circuit

• Red LED (D1) is on when battery voltage is 11.5V or less.
• Amber LED (D2) is on when battery voltage is comprised in the 11.5 - 13.5V range. This indicates that the battery is good if the car  is off. When car is running, this indicates no charge from dynamo or alternator.
• Green LED D7 is on when battery voltage is 13.5V or more. This indicates a normal condition when car is running and dynamo or alternator are charging.

R1,R3,R6    : 1K   1/4W Resistors
R2          : 100K 1/4W Resistor
R4,R5,R7,R8 : 3K3  1/4W Resistors
D1          : Red   LED 
D2          : Amber LED 
D3,D4,D5    : 1N4148 150mA Diodes
D6          : BZX79C10   10V 500mW Zener Diode
D7          : Green LED 
D8,D9       : 1N4148   150mA Diodes
D10         : BZX79C12 12V 500mW Zener Diode
Q1,Q2       : BC547   NPN Transistors
Q3          : BC557   PNP Transistor