Counters in multisim

[CdnMade]

I am attempting a project in Multisim.

Here are the details: i want to use a 555 timer, 3 74ls76 chips, 6 volt power supply, 7 segment display, and any nessary resistors, capcitors, nand gates. If nessary a wave generator can be used in place of the 555 timer.

This device must be able to count to 5 a total of 3 times. after the third 5 count the timer must stop and the 7 segment display must display a 3.

I have most of this done but am having a problem with 2 things. the first being that when i finaly get it to stop after the third 5. it displays a 1. Then if i make it so after it stops it displays a 3 the first run of the counter starts at 3. after 16 hours of work on this i am going crazy. I can email my MS file to anyone who wants to attempt to figure this out.

P.S i could not get the 555 timer to work and had to use a wave generator. not sure if its me or multisim.

 

[CdnMade]

ok after 20 hours i got it. ONLY one problem. when i restart my counter after the entire cycle. the counter starts at 3 for the first round then starts at 1 for the other 2. this only happens if i compleat the last step and make the 7 seg display a 3 at the end

 

[pebe]

Do you reset the counter when you restart?

 

[CdnMade]

i that is what i don't know how to do

 

[pebe]

You mentioned your counter was not starting at zero, which prompted my reply - I assumed you were using a decade or binary counter.

But when I look at your first posting I see you mention 74LS76. It was not readily apparent to me (because I only use 4000 series CMOS) that the chip is a J K flip flop.

I would normally reset a counter at switch-on by having a 1nf cap between the reset pin and Vdd, and a 10K resistor from reset to Vss. That assumes reset is taken high to reset. On switch-on, the reset would be at Vdd because the cap is discharged, so resetting the count. The cap would then charge through the resistor taking reset low and the chip would count normally.

Without knowing your circuit, though, I cannot see how you are using 74SL76 to count so don't know how to apply it in your case. More info would be useful.

 

[CdnMade]

if you email me cdnmade@hotmail.com i will return email you with the multisim file to look at if you don't have multisim then maybe i can save it in word or somthing for you.


i am lost and fustrated

 

[IRstuff]

7476 FF's should have both set and reset inputs. In your sim, you can create a reset condition that simply drives all your FF reset inputs and the releases them so that your counter starts counting.

TTFN

 

[CdnMade]

thankyou to those that helped. the counter is working great now.