helpless gal needs help with her circuit

[Fushigi]

Hi, My teacher has given me a project and using a 555 timer, and BCD counters 7490. My project criteria is :

1) make the timer a monostable of 1 minute.
2) make the counters into two divide - by 10 counters.

i have done all these and now she wants me to connect the timer to the counter to show a count of 100 within one minute. and at the end of it, an led must light up.

steps are:-
1) press trigger button to 555, timer on for 1 min. Counter starts to count. When count reaches 100, LED lights up.Counter stops counting.
2)To start new count, press trigger button again.

Can anybody help me on how the connection or do you have a simple circuit design that i can have cause i really dun know much about these and the worse part is i have to present it this friday... I know some gates must be used, like AND and OR.


hope to hear from helpers soon....
thanks

 

[GraveYard_Killer]

i saw an electronic counter last week. but i forgot the site. all i remember is that it uses a 74LS90 decade/binary counter connected to a 7 segment display, the site said that it could be put into series up to how many digits u want. maybe you could take a look for that IC as a temporary solution. then just play with transistor switchings if it hits 100.

 

[Optikon]

Hi, My teacher has given me a project and using a 555 timer, and BCD counters 7490. My project criteria is :

1) make the timer a monostable of 1 minute.
2) make the counters into two divide - by 10 counters.

i have done all these and now she wants me to connect the timer to the counter to show a count of 100 within one minute. and at the end of it, an led must light up.

steps are:-
1) press trigger button to 555, timer on for 1 min. Counter starts to count. When count reaches 100, LED lights up.Counter stops counting.
2)To start new count, press trigger button again.

Can anybody help me on how the connection or do you have a simple circuit design that i can have cause i really dun know much about these and the worse part is i have to present it this friday... I know some gates must be used, like AND and OR.


hope to hear from helpers soon....
thanks

You have a monostable which when pressed, gives you a timer = 1 minute. You say the counter has to count during this interval. So you will need another clock source to do the counting on your BCD's. When counter reaches 100, LEd lights up and counter stops. But what about if your 1 minute timer expires before counter reaches 100?

1 minute timer and counting to 100 circuits are easily done independently. You are not really clear as to how they relate to one another. Are you only allowed to count during the 1 minute interval? Or, are you counting 1 minute intervals 100 times?

If all you have to do is count to 100 within one minute, you do not need to have a one minute timer. Simply make your 100 counter go sufficiently fast! Incrementing your count every 600 milliseconds will count to 100 in 60 seconds. To do this in less than 60 seconds, just increment every 500 milliseconds for example.

I think your project wants you to combine the two circuits but you have not described the requirements correctly, Or I am missing something obvious.

 

[Fushigi]

more detailed requirements

My project is actually or will eventually be used to attach to a bio amplifier.This bio-amplifier calculates the heart rate.As a normal human heart rates can beat up to a 100beats per minute. thus, my teacher wants me to create a timer of 1 minute and two counters that count up to a 100. and by combining these two circuit. When a signal/pulse goes in,the timer will start timing and at the same time counters will start counting.So if the counters exceed 100 within a minute, the LED will light up.

by the way thanks for the tips.... :roll:

 

[Nigel Goodwin]

Re: more detailed requirements

My project is actually or will eventually be used to attach to a bio amplifier.This bio-amplifier calculates the heart rate.As a normal human heart rates can beat up to a 100beats per minute.

A human heart can beat considerably more than that, 100 isn't working hard at all.

From what I can remember from the gym, you maximum heart rate should be 220 minus your age. You should aim to train with your heart rate about 75% of that.

 

[Optikon]

Re: more detailed requirements

My project is actually or will eventually be used to attach to a bio amplifier.This bio-amplifier calculates the heart rate.As a normal human heart rates can beat up to a 100beats per minute. thus, my teacher wants me to create a timer of 1 minute and two counters that count up to a 100. and by combining these two circuit. When a signal/pulse goes in,the timer will start timing and at the same time counters will start counting.So if the counters exceed 100 within a minute, the LED will light up.

by the way thanks for the tips.... :roll:

Oh ok... see a little bit more info goes a long way...

ok two circuits... Make one of them the 1 minute monostable (you have this already?)

make the other one the count-to-100 circuit. This uses the BCD counters / decoders and display if you want. The input stimulus to make this circuit count will be the heartbeat or just a logic pulse for simulation purposes.

Then a little logic to tie it together. If the monostable output is true (meaning it is still timing < minute) AND the count >= 100 then light LED.
A couple of gates.

Use a few flip flops also.. use one of them that triggers the counter circuit based off of the timer-start signal (which may be some combination of start button and heartbeat pulse or whatever you want..)

Use another flop to latch the LED on so that if you counter design rolls over back to zero after so many counts past 100, you can keep th eindicator light on showing that 100 was exceeded in less than a minute..

These small details of operation are usually not thought about until the end.. so make it work nice by using some flip flops to latch signals...
If you really want a clean design, synchronize the whole thing with flip flops and provide and independent clock.. but I think this might be overkill for your project demonstration...

 

[Fushigi]

My teacher's Diagram for me

Well, my teacher said this would work but still after patching up everything, the led starts blinking and after 1 minute, just stays lighted up. is there anyway where i can improve on this circuit in the most simplest way?

really million of thanks to you experts out there, or i would be in a lost.

 

[Optikon]

Re: My teacher's Diagram for me

Well, my teacher said this would work but still after patching up everything, the led starts blinking and after 1 minute, just stays lighted up. is there anyway where i can improve on this circuit in the most simplest way?

really million of thanks to you experts out there, or i would be in a lost.

but what about the counting to 100? Your previous circuit doesnt do that. And the way the flip flops are connected is not recommended.