To begin with, I must say this is kind of a "homework" but I tried to do it on my own and I haven't succeed maybe someone can help me out with this matter. We're learning about digital systems, circuits and so on. Therefore, our next laboratoy is going to be about Monostable and Astable circuits (Using the timer 555). Being proactive I decided to have a look to the topic before having the class so I would understand better, the video showed the following circuit (which is a Monostable):


It was made in the software Circuit Wizard and I understood what are their differences and how those circuit work. However, when I tried to do it by myself I couldn't. The only little difference is that I used Circuit Maker and the elements seem to be different from the others used in the video. Here's what I got:

enter image description here

I hope you can see the unseen to make it work. I keep getting a message which says "the selected elements may not work in this simulation mode", is there a special "simulation mode" for this circuit? Thanks in advance.

  • \$\begingroup\$ As an aside, you usually don't want that top wire to appear broken like that when running it across the page. \$\endgroup\$ Sep 27, 2014 at 4:07
  • \$\begingroup\$ Got it, sir. I will take your feedback about the wires into account, thanks. \$\endgroup\$ Sep 27, 2014 at 16:19

1 Answer 1


1) Your LED current limiting resistors should be 300 ohms instead of 330k ohms.

2) DIS should be connected to THR, not to TRG.

3) VS1 should be a voltmeter, not a voltage source.

4) The connection to the junction of R4 and C1 should be made at the dot.

5) There needs to be 0.1µF between U1 pins 1 and 8. (Real World)

6) Why is the battery a MOSFET?

  • \$\begingroup\$ I did so. I followed your feedback from number 1 to 6 but I'm dealing with number 6. The battery appears to be different in this software, don't know if this is just me, but when I click on "search element" I'm able to find the battery. However this has the shape of a MOSFET, could this be replaced by a voltage source instead? Thanks a lot by the way you've been so kind for answering. \$\endgroup\$ Sep 27, 2014 at 5:10
  • 1
    \$\begingroup\$ Yes, definitely replace it with a voltage source. BTW, If you're going to be doing simulations, check out LTspice. Free, no nonsense, tutorials everywhere and pretty easy to learn, it's at: linear.com/designtools/software \$\endgroup\$
    – EM Fields
    Sep 27, 2014 at 5:37
  • \$\begingroup\$ I already did my "real-world" circuit replacing the battery with a voltage source without any success. I got a bad grade, but I'm keen on learning how this really works. I appreciate your suggestions, that software appears to be a good one. \$\endgroup\$ Sep 27, 2014 at 16:25
  • \$\begingroup\$ About the only thing I can think of that might still be giving you a problem is if S1 is being held made for longer than the 555's timeout time, which is about 1.1 R4 C1, or about 3.6 seconds. If that's the case, then the 555's output will just follow S1, with the output going high when S1 is pressed and low when S1 is released. What voltage is your voltage source outputting, BTW? \$\endgroup\$
    – EM Fields
    Sep 27, 2014 at 18:53

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