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Simple 555 Timer Simulation Issue

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irondeau 7 years ago

I am getting this issue when trying to run this simulation with the NE555P Timer. Circuit: gooduntitled Doing analysis at TEMP = 27.000000 and TNOM = 27.000000 Warning: singular matrix: check nodes r2_2 and r2_2 Note: Starting dynamic gmin stepping Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Warning: singular matrix: check nodes r2_2 and r2_2 Warning: Dynamic gmin stepping failed Note: Starting source stepping Warning: singular matrix: check nodes r2_2 and r2_2 Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful gmin step Note: One successful source step Warning: singular matrix: check nodes r2_2 and r2_2 Warning: singular matrix: check nodes r2_2 and r2_2 Warning: source stepping failed Transient solution failed - Last Node Voltages ------------------ Node Last Voltage Previous Iter ---- ------------ ------------- c2_2 0 0 r2_2 0 0 vcc 0 0 u1_5 0 0 doAnalyses: iteration limit reached tran simulation(s) aborted Error(parse.c--checkvalid): vprobe1: no such vector. ngspice-26 done This is my project: https://easyeda.com/editor#id=9f042bf1ab974c1ca5afcf386a1b2515 I'm not sure what needs to be done to fix this issue. Please respond soon. (Keep your answers simple please because I'm new to this.)

Comments

irondeau 7 years ago

I am also using this project as a reference for what I am trying to accomplish... https://i0.wp.com/www.circuitbasics.com/wp-content/uploads/2014/12/555-timer-astable-mode-circuit1.jpg

andyfierman 7 years ago

Hi Irondeau, Welcome to EasyEDA. Please use the 555_BJT_EE model found in **More Libraries...** under **System Components > Spice Components**. Please also search this forum for **555_BJT_EE** for more information about simulating circuits using a 555 timer.

andyfierman 7 years ago

Your circuit will not work because it has no power supply. * Please read and play with the examples in the EasyEDA Simulation eBook at: https://docs.google.com/document/u/1/d/1OWZVVFRAe_2NW3WratpkA_SGuHa5AcRow5ZRfvcoVTU/pub In particular: https://docs.google.com/document/u/1/d/1OWZVVFRAe_2NW3WratpkA_SGuHa5AcRow5ZRfvcoVTU/pub#h.1t3h5sf https://docs.google.com/document/u/1/d/1OWZVVFRAe_2NW3WratpkA_SGuHa5AcRow5ZRfvcoVTU/pub#h.46r0co2 :)

irondeau 7 years ago

Thanks so much for your help. I didn't realize that the VCC and GND were just flags and didn't actually supply any power. However, I've come up against another wall. I'm getting the same error that is found in this thread, which I see you also were a part of. :) https://easyeda.com/forum/topic/Convergence_and_No_Such_Vector_Errors_Simulating_Basic_Astable_555-LUSsqoljv If i am reading this correctly, it has to do with the fact that the 555 timer doesn't begin oscillating because it maintains a constant value of *whatever* at the time that the document is compiled. Am I correct in saying this? I don't quite understand what exactly I am supposed to do to get a pulse that starts the oscillation, but all I really want to know is if my circuit will do what I want if I get it printed out like this (once I design the PCB). I have some capacitors, LEDs, some resistors, and a 555 timer at my house. Could you just look it over for me and check that I have it right? Thanks again for all of the help you have already been!

andyfierman 7 years ago

`I don't quite understand what exactly I am supposed to do to get a pulse that starts the oscillation...` Configuring Voltage and Current Sources https://docs.google.com/document/u/1/d/1OWZVVFRAe_2NW3WratpkA_SGuHa5AcRow5ZRfvcoVTU/pub#h.2p2csry For info: these sources are in SHIFT+F > System Components > Spice SImulation > Spice Sources but you have already placed one for V1. To set up a PULSE Source, just click on V1 then select `PULSE` and set up the relevant parameters. To start up a supply rail in fact all you need to do is to set up: `PULSE(0V 9V)` This will produce a step at T=0 of from 0V to 9V with whatever the spice default risetime is. That's all you need. You can double click on the parameter text for V1 in the schematic and type the above expression straight in if you like. Then run the sim and look around it to see what's happening. You'll have to replace LED1 with one of: Dledy, Dleyg, Dledo or Dledr. These are very basic models for the low forward drop (roughly 2V) low power yellow, green, orange and red LEDs. I haven't built models for high forward drop blue, red, green and white LEDs yet. `Could you just look it over for me and check that I have it right?` You need to makwe sure that the PCB footprints that you assign to the schematic are suitable for the parts you already have. Don't forget that V1 is a simulation-only part: it will not be part of the PCB (unless you assign it a battery holder footprint) so just use a simple 2 pin header and then don't fit it so you can wire the battery holder wires straight to the holes in the PCB. See: https://easyeda.com/forum/topic/The_best_way_to_design_a_PCB_in_EasyEDA-ThR3pwqIC https://easyeda.com/forum/topic/How_to_assign_or_change_the_PCB_footprint_assigned_to_a_schematic_symbol-1SoiAuM4Y https://easyeda.com/forum/topic/Net_naming_conventions-uOHBvN5nh https://easyeda.com/forum/topic/Essential_checks_before_placing_a_PCB_order-UuohztL3l :)

andyfierman 7 years ago

Something else that you must include is at least 10uF directly across supply and ground of the 555 timer. You MUST decouple VCC pin of the 555 timers. If you use bipolar 555 type timers they have a huge shoot-through current spike (around 100mA for about 100ns) that can cause anything else on the supply rail to reset and pick up noise from the spikes. See https://www.youtube.com/watch?v=VfCu-siq0-Y for more. See manufacturers datasheet and apps notes for recommended decoupling: http://www.ti.com/lit/ds/symlink/lm555.pdf. This is less of an issue for CMOS 555 timer variants but is still important as general practice. See also: https://www.youtube.com/watch?v=VfCu-siq0-Y&authuser=1 If you were to model the supply source impedance and edit the 555_BJT_EE model to a local copy then you'll see that the effects of the 'supply shoot-through' current of the bipolar 555 but for the sake of convergence I have disabled it in the default model as it can lead to some very confusing convergence problems... just like the real device in fact!

tryagain10 7 years ago

I'm new to EasyEDA and just trying to get started. I have a dual 555 circuit working on the bench and thought I would practice in EasyEDA and simulate the circuit. Captured the circuit but could not get it to work. Went back to basics and captured a simple 555 bi-stable, but still it would not oscillate. After doing some research, I came across this posting and swapped out the 555 as suggested above - still no oscillation. I've tried to make my bi-stable public to share with you guys, but can't even get that working. I'm using v4.1.3. Can someone help to share and then help with the spice model please?

tryagain10 7 years ago

Just found how to make public. https://easyeda.com/editor#id=f36b31658a344f1fa8f85be0962bf1c7

andyfierman 7 years ago

Hi Tryagain10, Welcome to EasyEDA. 2 small mistakes: 1) You have set R5 1e-2 Ohms. In spice M = m = 1e-3 milli. Meg = Mega = 1e6 https://docs.google.com/document/u/1/d/1OWZVVFRAe_2NW3WratpkA_SGuHa5AcRow5ZRfvcoVTU/pub#h.3dy6vkm 2) As described above, you need to start up the supply or the voltage on C2 from zero: https://docs.google.com/document/u/1/d/1OWZVVFRAe_2NW3WratpkA_SGuHa5AcRow5ZRfvcoVTU/pub#h.46r0co2 * Note that with V1 as an ideal voltage source, C1 has no effect in the simulation. As stated above: * Please read and play with the examples in the EasyEDA Simulation eBook at: https://docs.google.com/document/u/1/d/1OWZVVFRAe_2NW3WratpkA_SGuHa5AcRow5ZRfvcoVTU/pub

andyfierman 7 years ago

You may also want to reduce the simulation times to: Max time step = 100n Stop time = 100u And note that the rise time of the envelope and falling frequency of the sawtooth on volProbe2 is due to the rising voltage across C3.

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