How do you make a digital counter circuit which counts to 10 minutes?

[fahadnajed]

I need to make a digital counter circuit which it counts to 15 minutes for my big project in my campus . When the circuit counts to 10 minutes, it will rings a buzzer. Same when it continues to 15 minutes, it will ring a buzzer again. (the circuit is for public speaking, so the speaker knows that he or she already went speak for 10 minutes and 15 minutes). We weren't allowed to use an Arduino, Microcontroller, PLCs, IC NE555, and a 4000 series CMOS IC but we were allowed to use breadboard, flip flop, decoder and 7 segments display. I'm kinda stuck here and I'm thinking it's impossible to make such a thing. Do you have any idea guys?

 

[mfb]

You'll need some oscillator. You can build them with just a few transistors, resistors and capacitors. If you can get a 5 minute cycle then you just need to count to 2 and 3, or use a 10 minute cycle and count to 1 and 1.5.

 

[alan123hk]

We weren't allowed to use an Arduino, Microcontroller, PLCs, IC NE555, and a 4000 series CMOS IC but we were allowed to use breadboard, flip flop, decoder and 7 segments display. I'm kinda stuck here and I'm thinking it's impossible to make such a thing

Is it allowed to use other series of logic ICs, such as HC, LVC, etc., or is it only allowed to make the entire circuit consist of discrete transistors?

Some logic series have entered the market for many years, and the oldest logic series has entered the fifth decade. The 4000 series appeared decades ago, and today there are many other options.
http://www.ti.com/lit/sg/sdyu001ab/sdyu001ab.pdf
If you really need to use a lot of discrete transistors to complete the task, then I think this is indeed frightening and difficult.

 

[Baluncore]

Reset everything to start. The output will be a three bit shift register made of D flip-flops. Every 5 minutes it is shifted once. The buzzer sounds for 1 second when the second or third stage goes high. (That needs an XOR gate with a D-F/F clocked at 1Hz).

Start with a 32.768 kHz watch crystal, divide it by two, 15 times to get 1 second period. That is the input clock for the timing logic.

5 minutes is 300 seconds = 2×2 × 3 × 5×5. (or; 300 = 256 + 32 + 8 + 4 ).
Use D-F/Fs to build ÷2, ÷3 and ÷5 arrangements of F/F.

The F/F count will be … 15 for prescaler, 10 for three hundred seconds, 3 for the output shift reg, 1 for the buzzer. Total = 29, which will come in 15 dual F/F chips + a few gates.

There are also simple digital solutions that are built from analogue step integrators and comparators. Take a look at sections 7.5 to 7.8 of the NSD application note 72, specific to the LM3900 quad current input amplifier.
http://www.ti.com/lit/an/snoa653/snoa653.pdf

 

[alan123hk]

If your main purpose is not to practice electronic circuit design, there may be other simple ways to achieve the goal, namely when the circuit counts up to 10 minutes, it will sound a buzzer... when it lasts for 15 minutes, it will sound Buzzer again.

You may edit and create an audio file to play a short melody when the time reaches 10 minutes and another short melody when the time reaches 15 minutes by a smart phone.
You may also simply record a short sound file using the microphone on your smart phone, and all you have to do is just generate the sounds at the specified times for the record.
However, the disadvantage of using only audio files is that no screen displays the remaining time.

There may be another more simple solution, just try to download a free Multiple Timer apps to your smartphone /tablet computer.

Of course you can add an external amplifier to produce the desired loudness of the sound

 

[tech99]

I need to make a digital counter circuit which it counts to 15 minutes for my big project in my campus . When the circuit counts to 10 minutes, it will rings a buzzer. Same when it continues to 15 minutes, it will ring a buzzer again. (the circuit is for public speaking, so the speaker knows that he or she already went speak for 10 minutes and 15 minutes). We weren't allowed to use an Arduino, Microcontroller, PLCs, IC NE555, and a 4000 series CMOS IC but we were allowed to use breadboard, flip flop, decoder and 7 segments display. I'm kinda stuck here and I'm thinking it's impossible to make such a thing. Do you have any idea guys?

Can you use two flip-flops with a time period of five minutes each? Than another to make the buzz.

 

[Baluncore]

Do you need to display the time or only make the sound at 10 and 15 minutes?

 

[fahadnajed]

Is it allowed to use other series of logic ICs, such as HC, LVC, etc., or is it only allowed to make the entire circuit consist of discrete transistors?

Some logic series have entered the market for many years, and the oldest logic series has entered the fifth decade. The 4000 series appeared decades ago, and today there are many other options.
http://www.ti.com/lit/sg/sdyu001ab/sdyu001ab.pdf
If you really need to use a lot of discrete transistors to complete the task, then I think this is indeed frightening and difficult.

Yeah sure, it's allowed to use logic gates and use discrete transistors. Well actually I was told to use any type of flip-flop, a counter and a decoder which is not built-in IC (it's seperate, each counter and each decoder). I told you, I don't have any point to make this, but I'm pretty sure I'm going to get ideas

 

[fahadnajed]

Reset everything to start. The output will be a three bit shift register made of D flip-flops. Every 5 minutes it is shifted once. The buzzer sounds for 1 second when the second or third stage goes high. (That needs an XOR gate with a D-F/F clocked at 1Hz).

Start with a 32.768 kHz watch crystal, divide it by two, 15 times to get 1 second period. That is the input clock for the timing logic.

5 minutes is 300 seconds = 2×2 × 3 × 5×5. (or; 300 = 256 + 32 + 8 + 4 ).
Use D-F/Fs to build ÷2, ÷3 and ÷5 arrangements of F/F.

The F/F count will be … 15 for prescaler, 10 for three hundred seconds, 3 for the output shift reg, 1 for the buzzer. Total = 29, which will come in 15 dual F/F chips + a few gates.

There are also simple digital solutions that are built from analogue step integrators and comparators. Take a look at sections 7.5 to 7.8 of the NSD application note 72, specific to the LM3900 quad current input amplifier.
http://www.ti.com/lit/an/snoa653/snoa653.pdf

I think I'm getting into this. You mean divide the 32.768 kHz by two which means change it into 1 Hz right? so it will produce a real time? Isn't? Why the 5 minutes instead 10 minutes and 15 minutes? Or is it the difference between them?

 

[fahadnajed]

If your main purpose is not to practice electronic circuit design, there may be other simple ways to achieve the goal, namely when the circuit counts up to 10 minutes, it will sound a buzzer... when it lasts for 15 minutes, it will sound Buzzer again.

You may edit and create an audio file to play a short melody when the time reaches 10 minutes and another short melody when the time reaches 15 minutes by a smart phone.
You may also simply record a short sound file using the microphone on your smart phone, and all you have to do is just generate the sounds at the specified times for the record.
However, the disadvantage of using only audio files is that no screen displays the remaining time.

There may be another more simple solution, just try to download a free Multiple Timer apps to your smartphone /tablet computer.

Of course you can add an external amplifier to produce the desired loudness of the sound

Thanks man, but my purpose here is to understand flip-flop and logic gates (which they are on my courses). I started practicing since last year which is my second year of college

 

[fahadnajed]

Can you use two flip-flops with a time period of five minutes each? Than another to make the buzz.

You mean by using two flip-flops with a time period of five minutes each will produce a buzzer? Heum.. I see that is no problem at all, but what I'm trying to do here is how to use a flip-flop, each counter and each decoder, to produce a buzzer at 10 minutes and 15 minutes

 

[fahadnajed]

Do you need to display the time or only make the sound at 10 and 15 minutes?

Well, I also need to display it by using 7 segments. Well, if I can make the sound at 10 minutes and 15 minutes, that would be great, but if I can make it just by a sign (maybe LED which acts as a sign), that will do the job

 

[rbelli1]

We weren't allowed to use an Arduino, Microcontroller, PLCs, IC NE555, and a 4000 series CMOS IC

Yeah sure, it's allowed to use logic gates

So you're allowed to use any series of logic gates but the 4000 series? Is there a specific reasoning for this?

BoB

 

[fahadnajed]

So you're allowed to use any series of logic gates but the 4000 series? Is there a specific reasoning for this?

BoB

Yes. Because my lecturer needs the students to understand the basic logic gates. In order to understand, we need to separate each counter and each decoder

 

[rbelli1]

Most or all of the 4000 series digital logic is available in the other series.

BoB

 

[Svein]

For that kind of accuracy - just filter the mains frequency (to remove noise), convert it to digital form and count down from that.

 

[alan123hk]

It seems that you mainly need the following components to make the apparatus.

1. Clock source (crystal oscillator / ceramic / RC resonator)
2. Several BCD counters
3. Several BCD to seven-segment decoders
4. Seven-segment display
5. Some flip flops
6. some logic gates and transistors
7. Active / passive buzzer

If the clock accuracy is not important, you may use RC resonator as clock source, in addition, you may only need two BCD counters/decoders if minute counting interval is also acceptable.

 

[sophiecentaur]

For that kind of accuracy - just filter the mains frequency (to remove noise), convert it to digital form and count down from that.

It would probably be best not be using a mains supply; batteries would do the job well enough and the device could be used anywhere. Making the clock oscillator would be a useful but easy task. I have had bad experiences with mains based clocks because they can be vulnerable to mains voltage spikes and other RFI.