Talkback for article: 253, September2002

Frequency counter 1Hz-100Mhz with LCD display and RS232 interface

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From: Alain Gauthier [ date: 2002-09-05 ]
Very nice and interesting article, as usual. Thank you for your contribution to the linux community.
From: Stefan Hager <nanotec(at)> [ date: 2002-09-13 ]
AVR Sounds really interesting!
A Frequency Generator would also be nice for me.
I bougt a few AVR chips months ago, but did'nt found any time to use them.
What i'd like to do with them is to make a MIDI controller for my external synths. For example with knobs to control the volume for on instrument.
I built a very basic 16-step sequencer some time ago with an AT89C2051 but the Program was to big for more then one channel :(
(But this one channel just works fine)

CU Stefan
From: marcus [ date: 2002-10-18 ]
very nice design
From: Manish Joshi <mj10in(at)> [ date: 2002-11-12 ]

The Circuit is Good .

Is this circuit can be used for manufacturing of Professional Frequency Counter ?

What is the sensitivity of this Counter ?

From: Ira Rubinson <ira.rubinson(at)> [ date: 2002-11-23 ]
Do you know of a frequency counter IC?
I'm looking for something that will do the following:

1Khz = 100mV or binary 10
2Khz = 200mV or binary 20
3Khz = 300mV or binary 30

Thans -Ira
From: guido [ date: 2002-11-23 ]
Hello Ira,
why don't you use this circuit? If you count only in the oder
of a few KHz then you don't need a divider and the circuit
is basically just one chip: the microcontroller
You can change the software a bit and you get your binary "10", "20", ...
If you use the PWM technology as described in the power supply article then
you can have in addition you DC voltages.
From: Armin [ date: 2002-12-01 ]
cool project !

Is there an alternative to the MAX903 ? (may be with changing the layout)
The only distibutor i found (in germany) wants >$15 and does not have the max903 on stock (> 3 weeks)


From: guido [ date: 2002-12-03 ]
Hello Armin,
there are alternatives but none is as fast and good as the MAX903.
Most alternatives will require additional power supply besides the
You can search for high speed comparators e.g at
They have similar chips but maxim has definitly the best solution.
From: Armin [ date: 2002-12-07 ]

thanks for you reply, i will try a search at philips but i think you have already done it ;-)

I think it would be the best way to try to get the max903.

From: Mike Durller [ date: 2002-12-08 ]

I am very impressed with your column. The Ateml AVR series of microcontrollers are my favorite. Keep up the good work. I want to build your frequency counter -- Please consider this a complement!


Mike Durller USA
From: Jesse <jfrey(at)> [ date: 2002-12-22 ]
I am very interested in building this frequency counter but I can not find the parts to make it. If you could tell me where I can find the parts I will make one. If anyone can give me locations in Iowa or on the net it would be helpfull. If you know of any place or web adresses you can email me at .
Design looks very good and interesting.


From: guido [ date: 2002-12-23 ]
Hello Jesse,
you live in the US!! This is where this stuff is made! Ok, maybe not
in Iowa but you should be able to find it. All parts are absolute standard
and I can get them even here at the local hobby electronic shop.
In europe you can also order them online at any of the bigger
shops for electronic parts: (germany), (france).

The only prblematic chip is the MAX903 but you can order it directly from
maxim (US company).
From: nyoman sumana <nyomans(at)> [ date: 2002-12-26 ]
can you help me to get those all IC because in my country it's hard to find.. so can you help me , i believe it can run nicely

From: guido [ date: 2003-01-01 ]
Here is a online store for US and canada that has all the parts
except for the max903 which you can get from maxim:
From: Florian Giezendanner <> [ date: 2003-01-04 ]
You can get the max903 in europe at
(unfortunately only the smd version)


From: Meng xiang_wei <uptonmeng(at)> [ date: 2003-04-24 ]
I need the device ,can you sale it? I want to measure the electromotor rate on a model boat.
From: Natale [ date: 2003-06-30 ]
What's the input impedance on this freq?

Best regards,
From: andrew <magolean(at)> [ date: 2003-11-12 ]
i would like to build your counter,so where can i get this components in south africa.


From: Oliver Ebert <sunnyboy(at)> [ date: 2004-03-02 ]
Hi Guido,

I built your frequency counter and it works fine. Thank you
for sharing the program and circuit schematics. Keep up your
good work.


Oliver (Germany)
From: Mehrdad Shahsavari <Mehrdad_Shahsavari(at)> [ date: 2004-03-07 ]
Mr.Mehrdad Shahsavari
5th floor,IDRO building
Jaame jam St.,Valie asre
Tel:++98 21 23862219
Fax:++98 212044035

Dear Sir/Madam

Industrial Development and Renovation Organization(IDRO)of Iran as the most entrepreneurial organization in our country is planning to produce DC electromotor
for the affiliated car manufacturing companies.
At the moment we would like to know at which capacity of production the plant is feasible and how much the cost of production is.By the way which companies you suggest for royalty and technology acquisition.
We look forward to hearing from you soon.

Yours faithfully
Mehrdad Shahsavari
From: Marian.S <kendallmarian(at)> [ date: 2004-06-23 ]
Hi Guido,

I have build the Frequency Counter and it works very well very accurate .I have used Max903 smd from Farnell and no problem.

Thank you for sharing the program and circuit schematics. Keep up your
good work.

I am looking forward for more projects , you are the master.

Regards Marian(UK)
From: Yap <seiweng.yap(at)> [ date: 2006-10-05 ]
I was fascinated by your project. But will it be able to measure a signal from speeches and sound? I heard that sound signal is between 20Hz to 20kHz. But there might be alot of parameters to be considered of course.
From: Glenn <glenn.fetalvero(at)> [ date: 2006-10-24 ]
sir you said that "We can not use directly the 74HC390 as a 1/100 divider because it can handle max 25MHz." but when i saw the 74hc390 from philips i saw that the maximum input frequency is 66 MHz. did you use a different manufacturer? thank you very much :D

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