# Building a frequency meter, Any advice?

Discussion in 'Homework Help' started by RTC, Feb 9, 2015.

1. ### RTC Thread Starter New Member

Feb 9, 2015
3
0
Hi

Currently at university at the moment in first year and been told as a project I must design a and build a frequency meter.

"you are required to design and build a circuit to display the frequency of a TTL compatible square wave wave. Frequency meters consist of a counter, a display and a gate that is opened and closed under the control of an accurate oscoscillator, plus some control. Your circuit should consist of three seven segment displays and indicate frequency in the range of 0-999hz. Your circuit should freeze the display when the gate closes so that it can be read, and reset it to zero before the gate opens again. It will therefore be necessary to design some gate and reset control circuitry, and possibly latch"

Above is the exact brief given.

I'm unsure where to start at the moment my lecturer has only taught us about gates so far.

So any help being that of youtube videos or websites to read to help me understand to design and build this would be great.

Many thanks
Rhys

2. ### Alec_t AAC Fanatic!

Sep 17, 2013
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Welcome to AAC!
Then your next step is to google for tutorials on counters and displays.

3. ### RTC Thread Starter New Member

Feb 9, 2015
3
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Cheers

Started doing that, but at the moment I'm struggling to understand how they all work togethe, to make a frequency meter.

Will that all become clear once I know enough about them?

4. ### IcedFruits Member

Jan 15, 2014
84
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try to understand something like a zero crossing detector ?

5. ### #12 Expert

Nov 30, 2010
16,665
7,310
TTL doesn't cross zero. You're going to be using digital chips to count highs and lows.

Start with a "block diagram". This is the input, it must have at least this much impedance and that much speed. This is the gate. It must open and close...how fast and how accurate? etc.

6. ### GopherT AAC Fanatic!

Nov 23, 2012
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4,019
You will need some time control system to open and close the gate (e.g. Exactly one second).

Here is the concept. The real work come in the 3-digit display! Not done here!

Jan 15, 2015
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Gopher laid out a good start. Just begin by looking at the blocks and what the building blocks each do. That drawing is a good illustration, really good.

Ron

8. ### RTC Thread Starter New Member

Feb 9, 2015
3
0
Cheers for all your help so far,

Looks like I have a lot of theory to learn first before I can start trying to tackle designing this.

9. ### Dodgydave AAC Fanatic!

Jun 22, 2012
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RTC likes this.
10. ### ScottWang Moderator

Aug 23, 2012
4,925
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You have to find the theory of frequency meter and how many functions it needed, and then solve them one by one, and put them together, the last is to test the function and debug.

11. ### GopherT AAC Fanatic!

Nov 23, 2012
6,303
4,019
Not so much. Look at the list of chip available in the 7400 series and then look into what they do. The datasheets are widely available and straightforward to read. If not, make another post on this thread.

http://en.wikipedia.org/wiki/List_of_7400_series_integrated_circuits

12. ### k7elp60 Senior Member

Nov 4, 2008
478
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I also think the block diagram is great.

13. ### wmodavis Well-Known Member

Oct 23, 2010
737
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I say gophers are much smarter than groundhogs. The GHs can't even predict the weather yet this gopher can simplify a frequency counter right down to the simple basics.

14. ### IcedFruits Member

Jan 15, 2014
84
2
thanks, missed the ttl part.