# 555n and 7490 problems

#### sokmo86

Joined Apr 13, 2009
10
need help here. this is for my project.

how to display 10, 30, and 50 using 555 timer and 7490 binary/decade counter??

my task is to design a shooting target system. currently i have already display 10, 30, and 50 by using 7447 ic. but the problem is now, how am i going to calculate the summation of all attempts. what i mean is i.e. 1st attempt, hit 10. the score will then display 10 n summation will also display 10. 2nd attempt, hit 50. the score will display 50 and summation will display 60 (10+50). 3rd attempt, hit 30. the score shows 30 and summation display is now 90 (10+50+30). how am i gonna display the sum??

i appreciate any suggestion or idea.

#### beenthere

Joined Apr 20, 2004
15,808
That is much too much to expect from just those components. A bitty microcontroller would be the most efficient way to do it. You could also assemble enough logic IC's for the functions, but it would be more expensive and much bigger.

As far as the display goes, you will need one 7 segment display per digit - so if your top score can be 150, that will be 3 displays.

How were you planning on detecting the hits on the target?

#### sokmo86

Joined Apr 13, 2009
10
currently, i'm using a limit switch for the detector.

so, how am i gonna sum all the scores? the project needs me to only use 7400 series ic's to design these shooting target. i already display 10, 30 and 50. if u have any idea, please assists me. tq. i'm planning to use 3 displays for the summation.

#### beenthere

Joined Apr 20, 2004
15,808
You could use the 555 as a clock, with a couple of BCD counter IC's receiving the count. External logic would monitor the pulses and stop the process at 10, 30, 50. If those counts accumulate on three counters in series, the process is just like adding.

#### SgtWookie

Joined Jul 17, 2007
22,201
Is this a homework assignment? It certainly sounds like one.

#### sokmo86

Joined Apr 13, 2009
10
You could use the 555 as a clock, with a couple of BCD counter IC's receiving the count. External logic would monitor the pulses and stop the process at 10, 30, 50. If those counts accumulate on three counters in series, the process is just like adding.
i dont quite understand what u explained. can u provide rough schematic diagram? or explain those above again. sorry. how to make the pulses stop at 10, 30 n 50.

@sgtwookie: sort of. but it's more to simple project. hope u can help too.

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#### sokmo86

Joined Apr 13, 2009
10
anybody, how to make a series connection for the 7490?? i want to connect 2 pcs 7490 in series. please help me.

#### Wendy

Joined Mar 24, 2008
21,840
A 555 monostable controlling a 555 oscillator could do the controlled pulse count. Figure a monostable to let a specific number of pulses go through.

An analog solution to a digital problem.

#### sokmo86

Joined Apr 13, 2009
10
A 555 monostable controlling a 555 oscillator could do the controlled pulse count. Figure a monostable to let a specific number of pulses go through.
i dont quite understand what do u mean. can u provide a simple example?? i've figured out how to connect two 7490 in series, but the problem now is, how to make it stop at 10, 30 and 50. hehe.

#### Wendy

Joined Mar 24, 2008
21,840
Pin 4 on a 555 is a enable/disable pin. If a monostable were feeding pin 4 then the oscillator will only be on when the monostable is high (timing). A specific duration of monostable will allow only so many pulses, and it should be repeatable.

Use the monostable on top and the oscillator on bottom.

#### beenthere

Joined Apr 20, 2004
15,808
Look at the outputs of your counters at any of those counts. Think of some external logic, like a NAND gate that might change state and stop the counting at any preset count.

Another way to do this is to use the target sensor (have you thought of that yet?) to do a parallel load onto a up/down counter like a 74160. Then you clock the count in the '160 into the totalizing counter.

There are several ways to do this, but you will need more logic to accomplish the project. Have you more resource than just the 7490's and the 555?

#### sokmo86

Joined Apr 13, 2009
10
below are the schematic of the counter i've constructed. 1st picture is the counter10, counter30 and counter50 in one picture. 2nd is the counter10, 3rd picture is the counter30 and the last one is counter50.

how i want to add the counter10, counter30 and counter50 together?? it should counting up. for example, 10+30=40 and so on.

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#### SgtWookie

Joined Jul 17, 2007
22,201
Look at a 74x83 or 74x283. They are 4-bit binary adders; they're the same except they have different pin layouts.

#### sokmo86

Joined Apr 13, 2009
10
the counter (10, 30, 50) is not 4-bit, can it works??

#### beenthere

Joined Apr 20, 2004
15,808
You are not really getting to a working circuit - there is no means of triggering the 555, and so on.

Are you limited to 7490 counters? Life would be much easier using an IC with a parallel load function.

#### sokmo86

Joined Apr 13, 2009
10
i can use any other ic but dont have any idea what ic should be used. if u can give me any idea, that would be good. thanx

#### sokmo86

Joined Apr 13, 2009
10
how if i want to stop 555 timer after certain time??

@beenthere: what are some example of IC with a parallel load function??

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#### beenthere

Joined Apr 20, 2004
15,808
Look up a 74160 for a counter with parallel load function.

Have you made a determination about how that limit switch is going to function? You will need a chain of logic to perform all the functions. In fact, this would be a good time to explicitly describe every thing that is going to happen (and how) when a score is made.