Looking for a free online circuit simulator

Discussion in 'Electronics Resources' started by Alexander Schubert, Jan 23, 2019.

  1. Alexander Schubert

    Thread Starter New Member

    Jan 23, 2019
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    Hi,

    I am new here so short introduction:
    German living in Latvia, studied engineering a long time ago, self employed (usually creating new domainsuffixes - such as ".berlin" - as in about to start a lightening device kickstarter project. Yeah; "Another damn LED light that nobody needs", you might think. Nope, it's not an APP-controlled device that outsmarts you by factor ten; it's a rather simple device that helps people with blue-light exposure problems (and yes: I am well aware that there are night-light blue-light-free products on the market).

    I won't be able to design the solution for my electronic device - but might be able to create a mock-up prototype myself. I have searched in the forum and in Google: but all online simulators that I found came up short regarding my specs.

    Here is what I need:
    Free (or low cost) online tool. Not a program, I want it ONLINE. "Free" not just in a sense of signup, but free = no or just very low cost (and the ability to save my creation). I do not need fancy "plotting" and what not. My product is essentially a simple light bulb of sorts and I need to simply test my circuit as if I have made a real one. I operate a switch and then want to see what happens (e.g. a delayed lightening up of the bulb). I do not need any "plotting". I need to see it working like a real life setup would work. And none of the existing solutions did that for me, or I am too stupid to figure our how it works, or they wanted a truckload of money. Some solutions seem to show the flow of the electrons - that made me very happy :D

    Think of a DC power source, a switch and a LED lamp: I want to operate the switch online, and see how the LED is lightening up (online). I need a SIMPLE tool. I stopped playing with electronic circuits at age 16 - my knowledge is somewhat diminished.

    Yes: I did search the forum. No: I obviously did not find a good solution here.

    Thanks a lot,

    Greetings from Riga, Latvia,

    Alexander
     
    Last edited by a moderator: Jan 23, 2019
  2. ericgibbs

    Moderator

    Jan 29, 2010
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    cmartinez and Alexander Schubert like this.
  3. Alexander Schubert

    Thread Starter New Member

    Jan 23, 2019
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  4. Alexander Schubert

    Thread Starter New Member

    Jan 23, 2019
    22
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    I tried it. I am not intelligent enough to operate it. I already failed just to add a DC power source - just couldn't find a way to do it. The tool is absolutely not intuitive or for beginners....
     
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Is this what you're looking for?
     
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  6. Alexander Schubert

    Thread Starter New Member

    Jan 23, 2019
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    Hi,

    YEAH! It's very intuitive, I can play around with the sliders, etc.

    Can store the result in Dropbox - so can use on different PCs.

    THANKS!
     
  7. wayneh

    Expert

    Sep 9, 2010
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    No one will argue with that! But it has advantages over the online simulators. You may want to keep it in the back of your mind if your needs change in the future. A big advantage is the simple fact that so many people use it. For instance if someone posts a model here I might take a look at it and try to answer the question. If I'm directed to some online simulator, I'll usually ignore the post.
     
  8. Alexander Schubert

    Thread Starter New Member

    Jan 23, 2019
    22
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    Thanks!
     
  9. ericgibbs

    Moderator

    Jan 29, 2010
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    hi Alex,
    If you post a diagram of your proposed design, we could quickly create a LTSpice 'asc' file, which you could run on your PC, assuming that you have LTS installed.?
    Doing it this way at least gets your project moving.
    E
     
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  10. Alexander Schubert

    Thread Starter New Member

    Jan 23, 2019
    22
    1
    Hi,

    the problem is that I need to play around to get a better understanding how transistors, thyristors and capacitors work together.

    The task is relatively simple:
    There is a 12 Volt DC power source. There are two DC electric loads (both 12V, about 7 watt each; e.g. DC motors). So we are talking about roughly 1 ampere. When I activate an old fashioned manual switch; this shall happen:

    DC load A is powered up.
    After 1 to 2 seconds (ideally variable) load B will be ADDITIONALLY powered up.
    End result: Both loads are powered up and shall STAY indefinitely powered up (up to several days).

    This seems trivial enough: In theory a capacitor, resistor and a thyristor (or transistor, I need to play around) should be able to handle that task I assume. I made such delay circuit at age 15 - that's almost 40 years ago. I forgot HOW I made it.

    However:
    If I switch ON the switch but then OFF within 1 second (before the 2nd load is fired up) and then ON again: Then the 2nd load should NOT be fired up; but load A should stay powered on. Obviously load A would fire up on "ON", then power off on OFF, then power on again on "ON": that's fine. I do not need continued powering up of load A during the brief 1 second long power off. However: I assume a big fat capacitor could do just that if need be (if we talk about just 7 watt load and less than a second time)? So: On/Off/On (executed within 1 second) leads to the 2nd load NOT being fired up. And STAY not being fired up: in extreme cases for hours/days.

    When switching the switch off (and it stays of more than about 2 or 3 seconds) the entire setup "resets": and is ready for the next session. So once we had the On/Off/On event and the 2nd load is cut off from power; to power the 2nd load on:
    the switch needs to be turned into OFF position, remain there a while (e.g. to have the trigger capacitor to empty itself through the high resistance resistor). That "resets" the configuration.

    Again: You guys probably roll on the floor and laugh and think: "I solved this at age 7 - what takes him so long"? I assume all that is needed is another capacitor that is flash loading once the switch is closed; then when to switch is opened it unloads VERY SLOW (parallel resistor of high resistance), so when the switch goes on again: THIS time we have a voltage from the capacitor and can use it as a "signal" - to permanently cut power to the 2nd load?

    It's probably too trivial for you guys here to even think about it. I might be able to create it - but I would need to play around....

    This all is just for a sub-solution of a prototype of my "invention" - the final product is a bit more complicated :D
     
    Last edited: Jan 24, 2019
  11. crutschow

    Expert

    Mar 14, 2008
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    That's not a trivial problem when you add in the momentary drop-out requirement.
    The easiest, and likely cheapest method (if you are worried about costs in production), would be to use a small microprocessor to perform this function.
    Are you up to learning some programming skills?
    Otherwise we can come up with a discrete circuit to do the job.
     
    Last edited: Jan 24, 2019
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  12. Alexander Schubert

    Thread Starter New Member

    Jan 23, 2019
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    Thanks for the offer!

    This is just for a MOCK UP PROTOTYPE. I can't start "learning programming" for something that simple.

    The first half (a simple 1 sec delay) seems solvable with just two resistors, a transistor and a capacity:

    https://homemade-circuits.com/wp-content/uploads/2012/05/simpledelaytimercircuit.png

    The second half should be similar - maybe involves a relais (or the electronic equivalent of one)?



    Again: Once I have an easy to understand and intuitive online circuit planner I simply play around and it should be not a real problem, right?

    But yes: The later "real solution" involves many more factors and I will need a design bureau creating a solution. Right now I need to have a simple "mock up solution". Without an 36 core cray computer working in the background :D

    Small Microprocessor: I assume the infamous "555"? At least that one seems to pop up every time one is googling "timer".....

    MOD: added the image.E

    AA1 24-Jan-19 17.34.gif
     
  13. ericgibbs

    Moderator

    Jan 29, 2010
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    hi,
    This is a LTS sim.
    E
     
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  14. crutschow

    Expert

    Mar 14, 2008
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    No, I was referring to small microcomputers, such as from PIC or the Arduino that can be programmed to do many different functions.
    A 555 is just a integrated circuit timer with no programmable functions.
     
    Last edited: Jan 24, 2019
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  15. Alexander Schubert

    Thread Starter New Member

    Jan 23, 2019
    22
    1
    Hi,

    thanks so much for investing efforts into helping me. Much appreciated. I think I understand the drawing. Thanks. Will try to play around with LTS simulation.

    Thanks from Riga
     
  16. ericgibbs

    Moderator

    Jan 29, 2010
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    hi,
    It would be wise to add a resistor in series with the switch.
    When you push the switch, the 1000uF will draw a high current thru the switch contacts while its charging up, say a 100R thru 1k.
    E
     
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  17. Alexander Schubert

    Thread Starter New Member

    Jan 23, 2019
    22
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    Hi,

    I see these tiny computers (or rather microcontroller if Arduino) since years. Seems the time has come ending hiding from them. First thing Sat morning will be marching into Riga's leading electronics store (yes, Riga has one) - and their website says they carry the Arduino. I buy a whole DIY Starter Kit and enlighten myself. Thanks for having converted me :D

    Greetings from Riga
     
  18. crutschow

    Expert

    Mar 14, 2008
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    Below is the LTspice simulation of a circuit using two CD4093 quad IC chips, a diode, and some resistors and capacitors that should do what you want.
    As you can see, B_On (green trace) doesn't come on for the first sequence of the SWitch signal (blue trace) since SW goes on/off/on.
    B_On does go on for the second sequence (starting at 6s) after a little over a second delay, when the SW stays on.

    The B delay can be made adjustable by using a 500kΩ pot for R1.

    upload_2019-1-25_11-40-16.png
     
    Last edited: Jan 25, 2019
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  19. Alexander Schubert

    Thread Starter New Member

    Jan 23, 2019
    22
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    WOW! Looks so cool. Thanks soo much for taking the time to having created that! Will try to wrap my mind around it!

    Thanks you!
     
  20. crutschow

    Expert

    Mar 14, 2008
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    Edit: I was able to simplify the circuit to use only one CD4093 quad NAND-gate chip. :cool:

    After S1 turns on, R6-D1-C4 provide about a 200ms delay before Reset goes high and the Latch becomes active, to provide S1 debounce protection.
    After S1 goes off, R5-C4 provide about a 2.5s delay before the circuit becomes active for the next activation.

    You would probably have to go with a microprocessor to get the circuit any simpler (eliminating most of the resistors, capacitors and diode).

    upload_2019-1-27_11-48-59.png
     
    Last edited: Jan 27, 2019
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