Train Circuitry Horn circuit The Horn Section
I was about to use the 555 IC to redesign the horn section then it occurred to me that some digital ICs now available could possibly do the job just as well and may be better than the last design .
The Horn section as been designed with the least number and basic parts possible. A good simulation is obtained, naturally the larger the speaker used (up to a point) the better the sound.
Experiment
The values shown for the capacitors and resistors used sounded pretty good . Only three gates are used as I found that by adding additional sound circuits interfered . The design allows for using trimmers instead of fixed resistances as well as different capacitance values of your choice for diffrent horn sounds . Use only non polarized capacitors polyester types have better sound .
Horn samples
Horn # 1 C11= .15uF , R7 =47K ,C14 = .002uF
Horn # 2 C11= .33uF
Horn # 3 C11= .15uF , C13=.02uF
Horn # 4 C11= .1uF , C13 = .02uF
Horn # 5 C11= .15uF , C12 = 1.0uF ,C13 = .1uF , C14 = .001uF
Make sure to connect all unsused pins to ground as shown . Pin 14 of the 40106 IC is connected to a push button ( N/O ) Normally open type which is used to connect the pos. (+)12 volts bus to activate the horn IC ( 40106 )
Amplifier
A additional amplifier is used for the horn circuit and is included on the PCB .It is similar to the diesel circuit except for the gain which has been reduced by adding a 8.2K resistor in series with the 10uF between pin 8 and pin 1 . The amplifier LM 386 must be hard wired connected to the positive and negative bus as shown . The gain can be adjusted if desired by adding any resistance value up to 10K or omitted altogether for a total gain of 200.
PCB
The PCB is shown as one circuit but it can be easily divided in two for convenience of enclosure choice and application . Take note of the red trace which is a wire jumper that must installed before the555 IC socket is soldered in .
Notes
Feel free to experiment with both circuit , But before you do that make sure you install IC sockets . You can also solder pins from which you could temporarely connect different component value to experiment with different sounds .
The horn module can be programmed in its own console by bringing out wire leads to switches and potentiometers to obtain different horn sound for different engines. Before you turn on the power do yourself a favour and trouble shoot your supply lines to the ICs and always reduce the volume controls to minimum to the amplifiers .
Have fun and send me an e-mail .
Train Circuitry Horn circuit
