Mullard Norbit Simulation Circuit

[sashdo]

Firstly, what an excellent program that has been created, it is brilliant!

I have been using it to try and create a simulation of some circuits I work with that use old Mullard NorBit components for training others and showing how they function. Using information from the forums I have progressed well. I firstly created the numerous separate "Cards" then progressed to wire them up as a system. The cards work well individually but I struggled to create a reliable timer that emulates the Mullard unit and had an issue with oscillation on one card that I just overcame manually as the actual circuit used capacitors to create a delay in the signal level. My issue came as I wired them together as a system,
several areas reported "wire not connected" when I activated the circuit, when I move the components around though they confirm that the pins/wires are connected OK (One example is the LED's on the outputs from the system as some remain grey and the fault lies within the card that drives them); I tried to delete and rewire but nothing appeared to resolve the issue. Have I done something incorrect or am I just at the limit of complexity for the underlying simulation?

I have attached my circuit to allow others to point me in the error of my ways.

I would like to try and get over this issue before I finalise the complete system but what I attach is 95% complete with only some external inputs missing.

[admin]

Hello,
I hope you have read the help pages on the web site.
You have built pretty big circuit and it hard to find the problem. You should test each component individually. There multiple ways of making sure the component is working correctly. If there is no state in it (like flip-flops or memory) then you can use truth table and filter expression to make sure it is doing exactly what it supposed to do. If you have state, then you can build a test circuit where you can manipulate it manually or use Python script to test it. You can look at the samples to see the test circuits.
It is hard to help you without understanding what the purpose of each individual circuit.
You also tend to build relatively big circuits. Try to make your components smaller. Also try to use spitters to combine inputs and outputs to multibit busses where it's logically makes sense.

[sashdo]

Thanks for the reply. Yes it is a big circuit but each of the individual "cards" was built and tested individually as it's own circuit before I imported them. The only thing I did after importing them was to swap buttons for inputs. One easy problem to see is with Card20 on the top right. One of the LEDs is grey and when you open Card20 the wire between the input and the NOT gate says it is not connected, but if you move the input or the NOT gate it shows they are connected as the wire follows them. Any ideas why?

[admin]

Well looks like the LED in question is connected via the connection chain: NOT gate on R_DRV - U24 pin - L9 pin on card2 - U29 pin.
The last pin is not connected to anywhere, so the entire chain gets optimized away and hence never been evaluated. Try to connect it to constant at least.

[sashdo]

Thank you very much for your suggestion, I had become so fixated with looking inside the first card I had forgotten to look further back in the chain. looks like I need to finalise all inputs before testing any further as I had assumed (incorrectly) that an unconnected pin would be assigned a 0.

To explain the circuit, it is the main sequence control for a gas turbine. It interfaces with some analogue systems to control speed and temperature, which have inputs to some of the circuits. Other interfaces are the buttons for commands and an alarm display (rows of lamps with driver/latch circuits). The design comes from the late 70's/early 80's period and it operates on 24Vdc. The function of the switch filter cards (Card 7&8) is to convert 100Vdc field voltage to 24Vdc for use in the logic then each card in turn has a specific function within the whole sequence of starting, stopping and protecting the machine. Card 19&20 are relay drivers and the Not gates are actually amplifier circuits that have an inverting effect.

[admin]

Ah, cool. Just in case you did not notice - there as a sensor input element that can be handy to simulate your analog input.

[sashdo]

I finalised my circuit and thought I would post here for pure interest. I also put in the zip some pics of the real life system.

Again, great piece of software. I think my final creation ended up being impractical as you can't manipulate the inputs fast enough, however I really enjoyed building it and learned things along the way The circuits of the individual cards will definitely be useful in showing others how the cards function