# Homework Help: Help on simulating a circuit - First attempt didn't work

1. Apr 19, 2014

### sampsoninc916

1. The problem statement, all variables and given/known data

The assignment for me is to simulate a circuit. I've already selected a project and I have already gathered parts thanks to my parents, but I need help on simulating the circuit. My first attempt did not go so well. The final steps of the project is to build the project on a breadboard, which I can do with my dad, and build it on a perf board, which I can do with my dad as well.

Here's the app I am using to simulate the circuit:

Here's the circuit I'm supposed to simulate:

The Circuit

2. Relevant equations

I just need to build the circuit, there really is no relevant equations as this is a project for assembling a circuit, not some help on homework or studying for a test.

3. The attempt at a solution

Here's my first attempt at doing the circuit:

http://l.bitcasa.com/C4FVbXxJ [Broken]

It did not work out so well because it did not become animated, like it was supposed to have simulated electricity flowing through it.

May you please help me on my second attempt to simulate the circuit. I believe the root of my problem is not understanding where what specific wires were supposed to go inside the IC1 555 Timer. I need to simulate the circuit by the end of this weekend.

Last edited by a moderator: May 6, 2017
2. Apr 19, 2014

### Staff: Mentor

Why did you re-draw the circuit in such a strange arrangement? In addition to being very hard to read, it looks like you have mis-connected several things, including the power supply connection for the IC.

I'd recommend that you draw the circuit in the simulation software exactly as it is shown in the example schematic.

Last edited by a moderator: May 6, 2017
3. Apr 19, 2014

### sampsoninc916

The simulation software only had an IC 555 timer that had 7 outputs, and they weren't even numbered, whereas the example schematic had 8 outputs and were numbers. Can you recommend me a circuit simulation software that can do just that? Why 7 and not 8? Why the strange th, tr, ctl, labels? Why couldn't they be numbered to make it easier for me?

4. Apr 19, 2014

### Staff: Mentor

You could try the free version of LTSPICE:

http://www.linear.com/designtools/software/?gclid=CK3A6-eS7b0CFUFrfgodrDcApg#LTspice

5. Apr 19, 2014

### sampsoninc916

6. Apr 19, 2014

### Staff: Mentor

Hmm, that's unfortunate. Try doing a Google search for NE555 spice model...

7. Apr 19, 2014

### sampsoninc916

8. Apr 19, 2014

### Staff: Mentor

Those two pinouts look the same to me. Check out the datasheet for the NE555, and it will probably show the circuit connections that you have in your example circuit.

9. Apr 19, 2014

### sampsoninc916

Where are the relays in LTSPICE? Here's what I currently have with building the circuit schematic:

http://l.bitcasa.com/s7LnX-v3 [Broken]

Last edited by a moderator: May 6, 2017
10. Apr 19, 2014

### mafagafo

There are many circuit simulators online. Falstad's seems too "experimental" to what you need.
LTSpice, as suggested should do just fine.
You could teach yourself a bit about it first. Check out some YouTube tutorials for it.
You may need to download some models to build what you want. LTSpice is not so fully-featured from start.

11. Apr 20, 2014

### sampsoninc916

I did the circuit in LTSPICE, but here's the schematic of my circuit, which the professor said looks good:

http://l.bitcasa.com/X-bpPMWt [Broken]

But here is the error dialog that pops up whenever I try to run the simulation:

Circuit: * C:\Users\user\Documents\waterlevelcontrollercircuit.asc

Error on line 4 : q4 n007 n021 n016 0 bc546
Unable to find definition of model "bc546"
Error on line 7 : q5 n017 n018 n019 0 pn2222
Unable to find definition of model "pn2222"
Error on line 8 : q6 n019 n022 n020 0 pn2222
Unable to find definition of model "pn2222"
Error on line 13 : d4 n020 n007 1n4007
Unable to find definition of model "1n4007"
Error on line 20 : d3 n005 n011 led
Unable to find definition of model "led"
Error on line 21 : q3 n011 n015 n007 0 bc546
Unable to find definition of model "bc546"
Error on line 24 : d2 n004 n006 led
Unable to find definition of model "led"
Error on line 25 : q2 n006 n012 n007 0 bc546
Unable to find definition of model "bc546"
Error on line 28 : d1 n003 n009 led
Unable to find definition of model "led"
Error on line 29 : q1 n009 n014 n007 0 bc546
Unable to find definition of model "bc546"
WARNING: Node U1:N003 is floating.
WARNING: Node NC_03 is floating.

WARNING: Less than two connections to node NC_01. This node is used by V1.
WARNING: Less than two connections to node NC_06. This node is used by R3.
WARNING: Less than two connections to node NC_07. This node is used by R2.
WARNING: Less than two connections to node NC_08. This node is used by R1.
Direct Newton iteration for .op point succeeded.
Singular matrix: Check node nc_02
Iteration No. 2
Fatal Error: Singular matrix: check node nc_02
Iteration No. 2

This circuit has floating nodes.