Forum - EasyEDA - An Easier Electronic Circuit Design Experience

Latest Topics Latest Replies EasyEDA Std EasyEDA Pro JLCPCB LCSC OSHWLAB General Discuss

Schematic PCB Simulation Skill Extension Feature Requests Bug Reports

Waveform not displayed after transient simulation

1201 3

Eusebius 8 years ago

Hi, this is a SPICE newbie question. I used a non-inverter amplifier circuit (with LM741) to play with SPICE simulation in EasyEDA: https://easyeda.com/editor#id=7mIC8NHBT When I launch a transient sim (be it with a 1V DC input or with a sine), I'm quite happy with the initial conditions shown in the results (at least regarding the nodes I have named myself), I'm reasonably happy with the 1012 data rows it claims, but I'm a bit frustrated by the absence of a waveform. What have I done wrong this time? My simulation results (1V DC input): Circuit: untitled Reducing trtol to 1 for xspice 'A' devices Doing analysis at TEMP = 27.000000 and TNOM = 27.000000 Initial Transient Solution -------------------------- Node Voltage ---- ------- xu2.11 14.9602 xu2.12 14.9601 xu2.6 -0.000858624 xu2.7 11.7991 vs 9.99926 xu2.53 12.4 xu2.54 -12.4 xu2.90 11.9991 xu2.91 25 xu2.92 -25 -vee -15 vcc 15 xu2.99 0 xu2.10 0.402537 v- 0.99989 xu2.13 0.416472 v+ 0.99996 xu2.14 0.416497 xu2.9 0 xu2.8 11.7991 e 1 h.xu2.hlim#branch -2.39982e-11 v.xu2.vlim#branch 0.0119991 v1#branch -8.02178e-08 v3#branch -0.00166656 v4#branch -0.0016667 v.xu2.vln#branch -3.69999e-11 v.xu2.vlp#branch -1.30017e-11 v.xu2.ve#branch 2.24001e-11 v.xu2.vc#branch 2.40154e-12 v.xu2.vb#branch -8.58624e-09 a$poly$e.xu2.egnd#branch_1_0 -0.0119991 No. of Data Rows : 1008 ngspice-26 done Thanks in advance.

Comments

andyfierman 8 years ago

Hi Eusebius, The problem net is the `v+` net with the `V+` probe you have placed on it. Nothing wrong with what you've done. It would appear that it does not like having a netname with a `+` in it *that is then the target of a probe statement* (check out the **Super Menu > Miscellaneous > Netlist for Document > spice** or **Download netlist** from the **Simulation Results** wndow to see this). ngspice is happy if you delete the volprobe so it's not the netname itself. The problem arises when you put the volprobe named `v+` ( or `v+` as spice is case insensitive) on the net. The causes ngspice to insert a `probe` statement for the voltage on the `v+` net. Like this: `probe V(v+)` I suspect the problem is that ngspice is then (erroneously) expecting to see something after the `+` character so it does not generate any probe data. There is clearly a problem in ngspice because it then does not throw an error or even a warning to say it can't show you a vector of results for `v+` (unlike the case for probing ground that I described in your earlier post). I think this is a bug in ngspice. Or perhaps just a quirk of the syntax of ngspice. ngspice is free and open source software but is nothing to do with EasyEDA. I will submit a bug report to them and hopefully it will get fixed quite quickly. It may take longer to ripple through to EasyEDA. * In the meanwhile the fix is simple! Don't use `+` or `-` characters in netnames. (BTW: you cannot use space characters either.) If you replace `V+` with `Vp` in the netname and the volprobe, ngspice is happy again. Also: for the same reason it is safest to rename `-VEE` simply to `VEE`. In fact `VEE` is negative by definition so the `-` character prefix is unneccessary and in fact confusing. Similarly for `VSS` in CMOS and other MOSFET circuits and chip. * Note: ngspice also sometime gets itself in a tizz when a `-` character is place in front of voltage or current in a probe or a other expression. In the unlikely (at your stage of spice useage) event that you encounter a need to negate a voltage or current, it is usually possible to avoid this problem by replacing an implcit negation by a `-` prefix with an explcit negation by `-1*`.

Eusebius 8 years ago

Thanks again for your swift reply and all the useful info. I knew about space characters, but I'll be more careful with other non-alphabetic characters now...

andyfierman 8 years ago

The ngspice manual itself is less than clear about the issue of naming conventions: http://ngspice.sourceforge.net/docs/ngspice-manual.pdf#subsection.2.1.3 :)

你现在访问的是EasyEDA海外版，建议访问速度更快的国内版 https://lceda.cn(需要重新注册)
如果需要转移工程请在个人中心 - 工程 - 工程高级设置 - 下载工程，下载后在https://lceda.cn/editor 打开保存即可。
有问题联系QQ 3001956291 不再提醒

Cookie Notice

Our website uses essential cookies to help us ensure that it is working as expected, and uses optional analytics cookies to offer you a better browsing experience. To find out more, read our Cookie Notice

Unleash creativity, start design now.

Cookie Notice