Computer Controlled Frequency Counter/Logic Probe


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Richard van Wyk 128,130 4 29
This circuit is a stable frequency counter accurate to 5 significant digits. The range is 0 - 30MHz with an input sensitivity of greater then 100mV. The probe connects to the PC serial port. So by using the crystal oscillator already present on your PC serial card and software calibration, the Probes' external circuitry is kept to a minimum. Probe 9 can also be used as a logic probe/analyzer using included software (LPROBE92.EXE).

Schematic

Schematic of the Computer Controlled Fequency Counter/Logic Probe

Parts

Part
Total Qty.
Description
Substitutions
R1,R2,R3,R44100K 1/4W Resistor
R5110M 1/4W Resistor
R6, R723.3K 1/4W Resistor
R81390 Ohm 1/4W Resistor
R911M 1/4W Resistor
C1, C420.1uF Ceramic Disc Capacitor
C2, C32100uF 16V Electrolytic Capacitor
D111N4148 Signal DiodeAny 200mA silicon signal diode
D2, D323.3V Zener Diode
D416.2V Zener Diode
U1174HC00 Quad Highspeed NAND Gate
U2, U3, U434021 8 Stage Shift Register
U5174HC393 Dual Highspeed 4 Bit Counter
U614040 12 Stage Binary Counter
MISC1PC Board, Wire, Suitable Probe, DB9/DB25 Connector

Notes

  1. Email Richard van Wyk with questions, comments, etc.

  2. The software to use this probe can be downloaded using the following link. Note that this software is compiled for Intel x86 platforms and runs under DOS, Win95, Win98 and WinMe. It does not run under any Windows version based on NT including Windows NT 3.51, WinNT4, Win2K, Win2K3, WinXP and Windows Vista. This is because NT based operating systems do not allow direct hardware access.

    Download Probe Software, Zipped, 19K

  3. SETPROBE.EXE is the frequency counter calibration program. To give accurate readings the Probe must be calibrated to your PC. SETPROBE.EXE calculates the constant error correction factor for the particular PC serial card the probe is to be used on. The frequency counter corrects for this slight constant error in crystal frequency by using the correction factor contained in PROBE.DAT. To calculate this correction factor, a reliable oscillator of known frequency (eg 2MHz Crystal Oscillator) is required. When CALIBRAT.EXE is run, the Probe will sample the frequency and then ask for the true frequency value in HZ. The frequency entered must be to 1 Hz accuracy (no decimal points) or an error will occur (for example "200123" not "200123.34" or "2003.421 kHz"). The program then calculates constant error correction factor and stores it to PROBE.DAT. Calibration is only necessary once.

  4. LPROBE92.EXE is the logic analysis program . Logic states are displayed in real time. This program runs best under DOS (not a DOS window). The sampling speed is adjusted by using the left and right arrow keys.

    The three triggering modes are:

    To Toggle between these use the UP / DOWN arrow keys. To quit from LPROBE press escape.

  5. FPROBE92.EXE is the frequency counter program. The measured frequency is displayed in Hz with commas indicating KHz and MHz. To quit from FPROBE press any key.

  6. Serial port pinouts are as follows.

    Line
    9 Pin
    25 Pin
    TD32
    RTS74
    DTR420
    DSR66
    CTS85
    SG57

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Comments

Add A Comment

anonymous
Computer Controlled Frequency Counter/Logic Probe
Wednesday, March 11, 2009 6:21:42 AM
this is almost unusable above 1-2 MHZ unless built VERY ADEQUATELY! used IC's will not click in a stable matter and the results will heavily depend on the shape of the signal. and shield heavily the box. COMMENT: tell me about this software & why it is not working in window XP (Editor's notes: NT based OSs don't allow direct hardware access.) there is a small program, that releases the port control, Direct IO if i am remembering right!
anonymous
Computer Controlled Frequency Counter/Logic Probe
Thursday, January 22, 2009 4:38:22 PM
I THINK is very useful, and I hope in the next mounth to make one. I will you send my opinnion. Thank you very much.
zeyad
Computer Controlled Frequency Counter/Logic Probe
Tuesday, January 13, 2009 4:16:20 AM
thanks a lot good topic
anonymous
Computer Controlled Frequency Counter/Logic Probe
Wednesday, August 27, 2008 11:54:02 PM
tell me about this software & why it is not working in window XP

(Editor's notes: NT based OSs don't allow direct hardware access.)

BaCaRdi
People don't you see
Thursday, February 21, 2008 11:00:29 PM
Thank you very much, I will definitely make this, I will however re-write the computer code so we can use the NT based platforms.
amar kudesia
Computer Controlled Frequency Counter/Logic Probe
Wednesday, January 09, 2008 5:39:08 AM
sir i want to know the whole theory & description of this project. Also i want the circuit diagram, its input & output connections for this project.
gregor
Computer Controlled Frequency Counter/Logic Probe
Tuesday, December 18, 2007 12:06:08 PM
have anyone a schematic or simple circuit diagram? or maybe you know internet shortcut about it?

(Editor's notes: Scroll up 6 inches.)

Giedrius
Computer Controlled Frequency Counter/Logic Probe
Sunday, December 16, 2007 10:34:07 AM
where i can get a circuit diagram of it;s. Does it work? R9 and C3 is missing... I want to construckt it
vivek
Computer Controlled Frequency Counter/Logic Probe
Friday, October 19, 2007 10:47:14 AM
this is good cicuit but tell something about softwere regarding this project.
anonymous
Computer Controlled Frequency Counter/Logic Probe
Friday, September 28, 2007 3:04:39 AM
This circuit is working please tell me how to bild this one can i use this circuit for mothr board repairing.
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