SPICE, Simulation Program with Integrated-Circuit Emphasis, has been around for 30+ years and is still an industry standard for modeling circuits to see how they'll behave. It can do transient analysis, steady-state, AC small signal analysis, DC transfer function analysis. You can model numerous devices and print and plot the results of the simulation. The tool remains text based, but with some menu wrappers for a few functions. Revisiting Pokey's Fan Motor Circuit: You may recall the crappy, last minute, motor driver circuit I threw together for Pokey, my firefighting robot. I want to use modeling to analyze the existing circuit and to help me come up with a better design.īut first, let's talk about SPICE. I found the following websites helpful, too: The MacSpice website has good documentation: Then I have to convert that into a SPICE circuit description file.įirst I have to draw the old motor circuit. The description file lists each of the components, and what nodes the components are connected to. Let's start with a much simpler circuit we'll ditch both transistors and represent the motor as a simple resistor, tying it directly to 9V and GND. Here's the circuit with the nodes labeled to make it easier to enter into a SPICE file. I spent about 2 hours trying to find out that I simply needed to number the ground node zero!! Note that the GND node must ALWAYS be node 0 or you will get errors like "Warning: singular matrix", "Warning: source stepping failed", "Warning: gmin stepping failed", "No convergence in DC analysis", and "failed to converge". A simple DC supply is described by Vname n+ n- value where n+ is the positive node, n- the negative node and value is the DC volts value. Next, there's the "motor" resistor described by Rname n+ n- value where value is the resistance, let's say 1Ω. (It has another option, the initial voltage, but we'll ignore that for now) The capacitor is described by Cname n+ n- value as you might expect. Note that SPICE can represent kilo, mega, milli, nano, pico, micro, etc. With a code (K, Meg, M, N, P, U, etc., respectively) so our 100♟ cap value is represented by 100U. * Capacitor in parallel on nodes 1 and 0, 100uF * Resistor in parallel on nodes 1 and 0, 1 ohm #Macspice oyunu code# Don't forget that or the component you put on the first line will be missing when SPICE analyzes the circuit! The first line of a SPICE file is always the title. So, create the file, example1.cir, and put the above text in it. You can load it into MacSpice (or whatever SPICE program you use) and analyze it. You may wonder what the op, and print statements do. The op command tells SPICE to analyze the operating point (steady state). The first print statement above displays the voltage at node 1, v(1), which is 9V as we would expect. In the next article I'll add more complexity to the model more complicated and do more with the analysis of the circuit.Key Features to come during Early Access: The second displays the current supplied by the v1 supply, i(v1).
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