Computer Controlled Frequency Counter/Logic Probe

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Author	Views	Views Today	Rank	Comments
Richard van Wyk	162,082	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

Parts

Part	Total Qty.	Description	Substitutions
R1,R2,R3,R4	4	100K 1/4W Resistor
R5	1	10M 1/4W Resistor
R6, R7	2	3.3K 1/4W Resistor
R8	1	390 Ohm 1/4W Resistor
R9	1	1M 1/4W Resistor
C1, C4	2	0.1uF Ceramic Disc Capacitor
C2, C3	2	100uF 16V Electrolytic Capacitor
D1	1	1N4148 Signal Diode	Any 200mA silicon signal diode
D2, D3	2	3.3V Zener Diode
D4	1	6.2V Zener Diode
U1	1	74HC00 Quad Highspeed NAND Gate
U2, U3, U4	3	4021 8 Stage Shift Register
U5	1	74HC393 Dual Highspeed 4 Bit Counter
U6	1	4040 12 Stage Binary Counter
MISC	1	PC Board, Wire, Suitable Probe, DB9/DB25 Connector

Notes

Email Richard van Wyk with questions, comments, etc.

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

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.

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:

TRIG: Starts each scan (left-right of screen) on a negative going edge of logic signal.
KEY TRIG: Waits for a key to be pressed before beginning each scan.
FREE RUNNING: Not triggered.

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

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.

Serial port pinouts are as follows.

Line	9 Pin	25 Pin
TD	3	2
RTS	7	4
DTR	4	20
DSR	6	6
CTS	8	5
SG	5	7

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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.

MABILA SAKHI Computer Controlled Frequency Counter/Logic Probe Saturday, September 15, 2007 5:27:17 AM

hi. i want to know about the working process of it's circuit. i want to know more about your project. from where should i get info. Theres any possibilities to make this schematic to be small.

prabhat Computer Controlled Frequency Counter/Logic Probe Monday, September 10, 2007 10:18:16 PM

could u plz send me all the details of this project as i am interested in making this project in my final year?

mostafa said Computer Controlled Frequency Counter/Logic Probe Friday, September 07, 2007 7:10:21 PM

sir i want to know the theory,circuit diagram, working and full detail about this..plz...send to me all details

deepti Computer Controlled Frequency Counter/Logic Probe Thursday, September 06, 2007 12:57:22 PM

sir i want to know the theory,circuit diagram, working and full detail about this.

rupesh Computer Controlled Frequency Counter/Logic Probe Friday, August 31, 2007 2:58:31 PM

sir i want know about its complete theory,working and display at output.and ckt diagram

vishal how can i display frequency, counted by microcontroller on my computer??? Friday, July 27, 2007 2:48:51 AM

or if it is possible then plz send me some idia about the software that will be useful to me to dusplay data on screen of my computer......

javed Computer Controlled Frequency Counter/Logic Probe Thursday, July 19, 2007 4:07:14 AM

dear sir i want to know about computer controlled frequency counter/logic probe with complete theory and where i can collect all the material so kindly inform me i am student of electronics engg so i want to make a project so kindly help me

COLLINS Computer Controlled Frequency Counter/Logic Probe Monday, July 16, 2007 8:02:51 AM

Pls can you give me a simpler circuit diagram, i want to construct it.

nobin Computer Controlled Frequency Counter/Logic Probe Wednesday, July 11, 2007 1:48:07 AM

hi i want to know working principle of this circuit

amol Computer Controlled Frequency Counter/Logic Probe Friday, July 06, 2007 11:31:46 AM

i want to know more about your project. from where should i get info

hiren information Monday, June 25, 2007 2:27:15 AM

hi. i want to know about the working process of it's circuit.

anonymous Computer Controlled Frequency Counter/Logic Probe Friday, June 01, 2007 8:46:35 AM

"Editor's notes: Probably a mistake on my part then" - are you going to de-do the schematic then?
(Editor's notes: It's just an error in the parts list. Ignore it.)

anonymous Computer Controlled Frequency Counter/Logic Probe Tuesday, May 01, 2007 2:14:11 AM

This is very good programe.I need circuit diagram of MICROPROCESSOR 8085

Do Not Interessa Computer Controlled Frequency Counter/Logic Probe Friday, April 13, 2007 8:19:59 AM

Where can I find this ready circuit?

Wilderlust! Computer Controlled Frequency Counter/Logic Probe Monday, April 09, 2007 8:56:15 PM

Hmm... i wonder how winscope and other pc test software overcome the problem with XP! Perhaps a different approach? Pity... I would have liked to have this tool.

dammy ehinmore Computer Controlled Frequency Counter/Logic Probe Saturday, March 31, 2007 10:45:40 AM

hi i just want to no about the computer thank u

slicker Computer Controlled Frequency Counter/Logic Probe Wednesday, March 21, 2007 6:31:00 AM

perfect circuit.......... i've tried it.

kathiresan Computer Controlled Frequency Counter/Logic Probe Saturday, March 17, 2007 8:05:46 AM

fine. but its little complex because you didnt use ic

pctek Computer Controlled Frequency Counter/Logic Probe Saturday, March 10, 2007 12:14:18 PM

I can't seem to find R9 or C3 on the schematic, the parts list shows C3 & R9.
(Editor's notes: Probably a mistake on my part then.)

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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.
MABILA SAKHI	Computer Controlled Frequency Counter/Logic Probe	Saturday, September 15, 2007 5:27:17 AM
hi. i want to know about the working process of it's circuit. i want to know more about your project. from where should i get info. Theres any possibilities to make this schematic to be small.
prabhat	Computer Controlled Frequency Counter/Logic Probe	Monday, September 10, 2007 10:18:16 PM
could u plz send me all the details of this project as i am interested in making this project in my final year?
mostafa said	Computer Controlled Frequency Counter/Logic Probe	Friday, September 07, 2007 7:10:21 PM
sir i want to know the theory,circuit diagram, working and full detail about this..plz...send to me all details
deepti	Computer Controlled Frequency Counter/Logic Probe	Thursday, September 06, 2007 12:57:22 PM
sir i want to know the theory,circuit diagram, working and full detail about this.
rupesh	Computer Controlled Frequency Counter/Logic Probe	Friday, August 31, 2007 2:58:31 PM
sir i want know about its complete theory,working and display at output.and ckt diagram
vishal	how can i display frequency, counted by microcontroller on my computer???	Friday, July 27, 2007 2:48:51 AM
or if it is possible then plz send me some idia about the software that will be useful to me to dusplay data on screen of my computer......
javed	Computer Controlled Frequency Counter/Logic Probe	Thursday, July 19, 2007 4:07:14 AM
dear sir i want to know about computer controlled frequency counter/logic probe with complete theory and where i can collect all the material so kindly inform me i am student of electronics engg so i want to make a project so kindly help me
COLLINS	Computer Controlled Frequency Counter/Logic Probe	Monday, July 16, 2007 8:02:51 AM
Pls can you give me a simpler circuit diagram, i want to construct it.
nobin	Computer Controlled Frequency Counter/Logic Probe	Wednesday, July 11, 2007 1:48:07 AM
hi i want to know working principle of this circuit
amol	Computer Controlled Frequency Counter/Logic Probe	Friday, July 06, 2007 11:31:46 AM
i want to know more about your project. from where should i get info
hiren	information	Monday, June 25, 2007 2:27:15 AM
hi. i want to know about the working process of it's circuit.
anonymous	Computer Controlled Frequency Counter/Logic Probe	Friday, June 01, 2007 8:46:35 AM
"Editor's notes: Probably a mistake on my part then" - are you going to de-do the schematic then? (Editor's notes: It's just an error in the parts list. Ignore it.)
anonymous	Computer Controlled Frequency Counter/Logic Probe	Tuesday, May 01, 2007 2:14:11 AM
This is very good programe.I need circuit diagram of MICROPROCESSOR 8085
Do Not Interessa	Computer Controlled Frequency Counter/Logic Probe	Friday, April 13, 2007 8:19:59 AM
Where can I find this ready circuit?
Wilderlust!	Computer Controlled Frequency Counter/Logic Probe	Monday, April 09, 2007 8:56:15 PM
Hmm... i wonder how winscope and other pc test software overcome the problem with XP! Perhaps a different approach? Pity... I would have liked to have this tool.
dammy ehinmore	Computer Controlled Frequency Counter/Logic Probe	Saturday, March 31, 2007 10:45:40 AM
hi i just want to no about the computer thank u
slicker	Computer Controlled Frequency Counter/Logic Probe	Wednesday, March 21, 2007 6:31:00 AM
perfect circuit.......... i've tried it.
kathiresan	Computer Controlled Frequency Counter/Logic Probe	Saturday, March 17, 2007 8:05:46 AM
fine. but its little complex because you didnt use ic
pctek	Computer Controlled Frequency Counter/Logic Probe	Saturday, March 10, 2007 12:14:18 PM
I can't seem to find R9 or C3 on the schematic, the parts list shows C3 & R9. (Editor's notes: Probably a mistake on my part then.)