Frequency Counter

[inferno]

ei! help me with circuit.. i want to change the semiconductors...will you please suggest a substitute for this.. tnx!!


Resistors (all 1/4W 5% carbon film)

R1,R9      1k (brown, black, red, gold)
R2,R10,R11   470R (yellow, purple, brown, gold)
R3,R13      10k (brown, black, orange, gold)
R4      1M (brown, black, green, gold)
R5      2k2 (red, red, red, gold)
R6,R8,R15   220R (red, red, brown, gold)
R7      10R (brown, black, black, gold)
R12      560R (green, blue, brown, gold)
R14      100R (brown, black, brown, gold)
R16-R23      330R (orange, orange, brown, gold)

Capacitors (electrolytics 2.5mm spacing, others 5mm)

C1,C4,C6   100u electrolytic 16V
C2,C5,C7   220u electrolytic 16V
C3      100n miniature polyester
C8,C11      100n ceramic
C9,C10      22p ceramic

Semiconductors

TR1,TR3,TR4   BC549B npn transistor (or BC547B, 48C etc.)
TR2      BF244A or B N-channel JFET
TR5      ZTX313 npn switching transistor
D1-D3      1N4148 silicon diode
D4      BAT42 Schottky diode
REG1      LP2950 5V regulator
IC1      18-pin DIL socket + PIC16C54 HS/P microcontroller
DISPLAY1,2   0.56" dual 7-segment LED display, common cathode

Miscellaneous

X1      20MHz crystal, HC-49/U case
S1      miniature pcb vertical slide switch, SPDT
INPUT      BCN pcb socket
BATTERY      PP3 battery snap

4 x rubber feet


...... below is the schematic.....

frequency_counter.pdf

 

[audioguru2]

Hi Inferno,
Why do you want to change the semiconductors?
It looks like a very nice project that is designed to use those ones.

If you can't get the parts, or don't want to program its microcontroller, then just buy the kit.

I'll bet that it eats batteries because of its LED display.
At first I thought that its voltage regulator will also eat batteries, because it is still powered even though the rest of the project is turned off. But then I realised that it is a special low-power regulator, and that the microcontroller needs a very quick power-up to properly reset.

 

[absolution]

2n3904s are nice but somewhat expensive compared to various others. just get datasheets most of the replacements you can find at your local radioshack.