Simple 10KHz time base

[Boncuk]

Hi to all,

I was asked by a student to help him with a class project which is measuring the speed of a moving object using two light barriers. The measuring distance is just one meter and therefor requires accurate timing.

I am also afraid they don't possess a frequency counter at school to adjust a timer circuit which will deliver precisely 10KHz. I looked up ceramic resonators, but the lowest frequency to obtain is 400KHz which would result in several divider ICs.

Does anybody know of a circuit meeting above requirements? Stable and accurate fixed frequency without much additional circuitry?

Thanks

Boncuk

 

[Brevor]

I think your idea of using a 400 Khz resonator is a good one.
It could be done with just 2 low cost IC's.
You could first divide by 10 with a 4017 to get 40 Khz, then follow that with any binary counter such as 4024,4520 or several others to divide by 4 to obtain 10 Khz.

 

[Leftyretro]

A lot of the newer and not expensive digital multimeters have a frequency counter mode using the AC volts input fuction. A DMM would be a good classroom addition and would let you adjust simple timer circuits.

Lefty

 

[Boncuk]

Thanks to both of you,

I guess I will use the 400KHz resonator. A frequency counter does not quite meet the requirement which is time measurement, and I don't know about the arithmetic abilities of the students of that school to convert frequency to time.

Secondly I don't know the budget of the school either. :confused Since it is a class project I suppose that all the measuring devices have to be built by students.

Kind regards

Bosco

 

[Super_voip]

If there's no frequency counter why not use a 20KHz crystal, they do exist, I have one. A simple divide by two gets 10KHz. An alternative might be to use a RC circuit and a digital votmeter, try to scale the R & C so you stay in the roughly linear section of the curve

 

[Nigel Goodwin]

A frequency counter does not quite meet the requirement which is time measurement

Actually, most frequency counters also do time measurement!.

 

[Leftyretro]

Thanks to both of you,

I guess I will use the 400KHz resonator. A frequency counter does not quite meet the requirement which is time measurement, and I don't know about the arithmetic abilities of the students of that school to convert frequency to time.

Secondly I don't know the budget of the school either. :confused Since it is a class project I suppose that all the measuring devices have to be built by students.

Kind regards

Bosco

Time (period) = 1/Freq, simple long division

Lefty

 

[Boncuk]

Hi Lefty,

I know it. Do the kids know it too?

Boncuk

 

[on1aag]

Accurate 10 kHz timebase.

Hi Boncuk,

Check this out:

https://www.electro-tech-online.com/custompdfs/2007/11/jupiter-gps-board.pdf

The module costs about € 30 and an additional € 10 for the antenna.
You gonna have to build the computer interface yourself but that's no
big deal, everything you need to know can be downloaded from that site.

on1aag.

 

[jpanhalt]

Hi to all,

I was asked by a student to help him with a class project which is measuring the speed of a moving object using two light barriers. The measuring distance is just one meter and therefor requires accurate timing.

As an alternative to the approaches already mentioned, when I was faced with a similar problem for my son's pinewood derby, I simply hacked the start-stop switch of a WalMart $8 stopwatch (0.01 second precision) and used off-the-shelf IR emitter/detector units for the light beam from radio Shack. John

 

[Boncuk]

Hi, to on1aag,

are you sure a GPS-module is the right equipment to measure the speed of toy car? May be you got confused and wanted to post that answer for another thread.

to jpanhalt,

the idea is good and simple. However I cannot simulate parts which are not available in Thailand.

This is my final descision: I'll make a timer circuit using an NE555. It will be adjustable within a small range to compensate for tolerances of Rs and Cs.

Regards

Boncuk

 

[Nigel Goodwin]

This is my final descision: I'll make a timer circuit using an NE555. It will be adjustable within a small range to compensate for tolerances of Rs and Cs.

So accuracy and repeatability aren't concerns?.

 

[Boncuk]

10KHz time base

Hello Nigel,

of course accuracy and repeatability are of concern. However I don't want to pass a circuit to anyone which I did not test before. Testing a circuit with a ceramic resonator is impossible here in Thailand for two simple reasons. First, nobody knows what is a resonator and secondly there is none available.

Regards

Boncuk

 

[Nigel Goodwin]

of course accuracy and repeatability are of concern. However I don't want to pass a circuit to anyone which I did not test before. Testing a circuit with a ceramic resonator is impossible here in Thailand for two simple reasons. First, nobody knows what is a resonator and secondly there is none available.

There is certainly plenty of equipment manufactured in Thailand that uses ceramic resonators, it's just a cheap replacement for a crystal - not as good, but often good enough.

 

[Boncuk]

Hi Nigel,

there are certainly ceramic resonators used in Thailand, mostly for IR-remote controls which are operated at 455KHz. All the electronic parts being sold here are parts of overproduction or obsolete parts. You can find tons of PCB-connectors, but just the connectors, no wafers!

May be I could find a suitable resonator in Bangkok Chinatown - after a search of two or three days. There are about 5.000 shops in Chinatown and most of the offers is just junk.

Please forgive me, but Asia is not similar to Europe.

 

[Pommie]

Can you get hold of pic chips. Something like a 12F683 would be a very good single chip 10KHz source, assuming you could program it. A 16F627 could do the complete timing and display the result.

Mike.

 

[Boncuk]

Thanks a lot, but this is a school project.

Using an MCU they will end up using a crystal anyway, a PIC + programming hardware.

Boncuk

 

[Hero999]

I have some 10kHz oscillators I can send you if you're willing to pay shipping.

 

[Boncuk]

10KHz time base

Hi hero999,

of course I will pay for the shipment - and the parts too.
Provision: really accurate and adjustable to 0% tolerance, if possible CMOS-level.

Just give me details.

Regards

Hans


P.S. What is the difference between an english and a german hero? The english hero is alife while the german can only be a hero - dead.

 

[audioguru]

Hi Hans,
Are you Herman the German at Electronics-Lab???