Problems with Simulating a Timer Circuit

[DavidFFA]

Hello, I'm very new to Multisim, a week old. I'm trying to recreate this timer circuit shown but it is not giving the expected results, nor is it simulating well. I'm sure this is littered with newbie errors, (my engineering is out of practice as well).

Attached is a picture of what the circuit supposed to be, and what I did with it in Multisim. Any help is greatly appreciated.

The ideal operation is supposed to be that the 4060 is supposed to create the timing pulses for the 4017, which would be counting down. The four way switch would allow to pick a timer setting of 30 seconds, 1min, 2min and 3min. The LED's would light up in sequence as the time ran closer to finishing its count. Upon finishing, the buzzer would ring and the final LED would light up.

[SimpleEric]

Hello. The 4060 does not work properly. See http://forums.ni.com/ni/board/message?board.id=370&message.id=203&query.id=22480#M203

W.k.r.

[NatashaB]

The issue with the 4060* model in the attached link was fixed for V10.1.  It seems that you have the updated model though, so I don't think that's the issue...

Message Edited by NatashaB on 01-13-2010 04:18 PM

[SimpleEric]

Hello NatashaB. I haven't got 10.1, only 10.0.1. Does that mean that we are using different models when viewing (simulating) the design - or is the new 4060 model included in the design from DavidFFA?

w.k.r.

[NatashaB]

Eric,

The model would be saved at the circuit level, so you should be seeing the updated model even though you are opening it in 10.0.1.

[Tien_P]

Hi David,

I made some changes to your circuit wiring and it appears to be working now.  

1.  I connected a 680 ohm resistor to each of the LEDs

2.  I rewired the power and ground using a DC source and analog ground for the main circuit and I used VDD and VSS for the digital ICs.  Have a look at this KB for more to see how to wire digital ICs. 

Message Edited by Tien P on 01-14-2010 09:59 AM

[SimpleEric]

Hello. The major parts of the circuit now works, but there are some minor flaws in the design that can bee seen in the simulation. Some of the flaws

will probably not be seen in a real-world circuit:

See the file gamertimer_b. Note that I have added the clock voltage V3 to speed things up. This is only for testing.

1) LED10 never lights up because it only reaches 9.48 mA. Changing R16 to a lower value (560 Ohm) will fix this, but I chose to change the LED

on-current to 9 mA instead of 10, because the LED will work in a real circuit without changing R16.

2) A pull-down resistor (33 kOhm to GND, R3) is needed after the switch J2 to prevent the MR signal from floating when J2 is open. Can be a problem

in the real circuit.

3) The RC net around U1A creates a delay after LED10 has been activated - and starts the buzzer after a couple of seconds (that is what I think the

designer intended). Problem: C4 is charging even if LED10 is inactive (see the voltage measurement probe). This means that the buzzer sometimes

will start immediately when LED10 is activated. Some kind of circuit that prevents C4 from charging is needed.

4) Putting a resistor at every LED works as a way to fix the simulation, but one common resistor for all LEDs will work in a real circuit (because only

one LED is active at a any time). Since there is a problem with the LED models, I used a LED bar that works better (see LED11).

5) If J2 is open when the simulation starts, 4017 often displays a random code at the outputs. Close J2 to reset the 4017. A start-up reset would be

nice.

See the file gamertimer_c2. Most of the problems have been fixed with the new design. Toggle switch J1 to select the actual clocking or the fast

test-clocking. In the original design the buzzer will toggle on/off, in this design it will stay on until J2 is grounded. Increase R18 for a longer buzzer

delay. Set the LED11 to 9 mA.

W.k.r.

[SimpleEric]

Hello again. Ignore point number 3. It is not seconds, made an error in calculating the time constant. It now looks like it just makes the buzzer sound differently. The other points are still valid.

W.k.r.

[stryzbiak]

I put a simple 555 timer in Multisim and it does not seem to flash the lights properly. I built the circuit and it flashes like it should, about 1flash per second. The simulator shows it flashing at about ine flash every 4 seconds.  What do you think?

I can't see where I can post without just replying to someone else.

Thanks,

Sid