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Challenges using LTspice


david_mackay00

 

I have a fairly simple circuit in DS PCB (resistors, capacitors, transistors, a NE555, relays, and some 74-series logic) both as a schematic and routed on a PCB. All standard stuff.

I’m trying to use LTspice for the first time, through the DSP PCB Output menu. I’d naively assumed that DS PCB would export something that LTspice would understand. But I’m getting lots of errors. Just a few examples below.

Error on line 11 : u3 n0096 n0097 unconnected1 555

       Unable to find definition of model "555"

 

Error on line 21 : d1 n0184 n0186 diode

       Unable to find definition of model "diode"

 

Error on line 33 : mq4 n0557 n0516 n0278 2n7000

       Unable to find definition of model ""

Error on line 55 : led7 n0547 0v led 5mm red

       Unknown parameter "led"

 

I’m a little confused. The diodes are 1N4148. The transistors are 2N7000s. The NE555 is one of the most common ICs around. DS knows these components, why can’t it create an export that contains this info? I know I can add “SpiceDevice” values to components and had to do this for all the NMOS transistors with "SpiceDevice=M" - but why doesn’t DS take care of this?

 

Then I’ve got “Fatal Error: URC instance U5: Length must be positive definite”. I think this refers to a delay line stage formed from a resistor and capacitor. DS knows the values of these components – what additional info is LTspice asking for?

 

 

Is this what you would normally expect to see using LTspice? If so, it’s probably not for me. Is there a better alternative simulator to use that DS can correctly export to that doesn't need me to tell it what all the components are? I understand for exotic components I might need to add meta-data, but not for standard components. Or am I missing something obvious?

 

 

 

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