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Unable to solve convergence error

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I've reverse engineered a diode based thermostat which uses a 1N4148 as the temperature sensor.

 

I've entered the circuit into the schematic editor, but whatever I do it refuses to run the simulation!  I get an immediate "Timestep too small" simulation error, and the convergence assistance cannot solve it.

 

I'm don't *think* I've got any "stupids" that would cause the simulation to fail, but maybe I missed something obvious.

 

As a "Starter for 10 points" how can I get this simulation to run?

 

As a "Bonus question for 30 points" how can I change the temperature of the diode to (say) 150C while leaving the rest of the simulation at nominal temperature?

 

 

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I got rid of a singular matrix error by putting a DC power source and lamp on the relay output circuit, but it still fails to simulate.

 

I attach the updated model

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Solution
Accepted by topic author david_c_partridge

Hello,

 

Let's use a better SPICE model for the LM324N:

 

  • Double-click this component (U3A) to open its Properties.
  • Select the Value tab and click on the Replace button.
  • Make sure that the LM324N is selected in the Component Browser.
  • Go to the Model manuf./ID field and selec the model from National National Semiconductor (this is a 5 pin model, more precision).
  • Click OK, select section A.
  • Repeat this process for section B, C and D.

 

Run the simulation, this convergence error should dissapear. I've attached your circuit with this modification.

 

Hope this helps.
Fernando

Fernando D.
National Instruments

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Yes, definitely plenty of Brownie points for that  The circuit now works with some tweeks to the relay on current.

 

I''l open another thread on how to adjust the temperature of JUST the 1n4148 diode (to change VF)?

 

 

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Hi everyone,

 

I'm having the same convergence issues with a circuit I'm trying to simulate. Can somebody please run it and see if he/she can figure out what I was doing wrong.

 

I've attached the circuit. 

 

Please explain how you fixed it.

 

Thanks

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Wadel,

 

You have the power supply going to pin 8 (VCC) of the LM358 reversed.

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Thanks Tom.Smiley Very Happy

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I working with a solar inverter circuit. I keep getting the convergence error message. Any ideas on what might be wrong?

 

Schematic.PNG

 

 

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Your AC ground and DC ground are same. Avoid same ground for AC and DC

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