First of all, I have not designed the circuit neither I asked questions about this proven-to-work-really-well circuit. This is only the 3rd time that I use KiCad’s simulation tool, and I am asking if I am doing something wrong in the simulation tool because I suspect so. This is where this topic is about.
I do will answer some questions.
They are intended for extra heat dissipation. Switching may happen via a decoder device which switches the load with a transistor or a manually operated physical switch.
Some of the loads (point motors) have limit switches. They disconnect the driving coil physcially. But not all of them.
If you don’t have a limit switch and you hold down the button too long and you supply with 18V. There can be power dissipation of roughly 0.65W in those resistors. I tend to use 1206 SMD resistors, so I put 4 in parallel. This costs next to nothing and it does not hurt.
That’s pretty simple, but lacking, because your circuit does not limit the pulse time to the points.
It is not lacking because the capacitor will start charging again as soon as you let go of of the switch.
The original design used THT resistor. The transistor is also rated to 4A. Whether this is actually needed I cannot yet tell, that is where is simulation is for.
Current in D1 perhaps?
For now yes. In the future I want to add more measure points ofcourse. But I do want to know the charge current flowing through D1
What that means? Specially ‘without affecting the PSU’.
CDU does 2 things.
It prevents voltage dips on the power output lines during switching actions. In the old days when you would set a switch, you would see your lighting dim. At this time we still used old transformers. CDU solves this issue.
CDU can supply like 7A or more. While it only draws a small current of around 0.5A or less from the PSU. If I would switch one of those coil drive abomination which consume 7A (these exist), my 1A meanwell PSU will go into short circuit mode or so. With the CDU in between my 1A PSU can supply a 7A point motor just fine.
I am guessing he intended to build something like:
I assume you want to build a constant current source,
I am sorry but your assumptions and guesses don’t come close.
Back to the topic.
In the simulation I am looking at the pink dotted line I(V1) I am seeing a negative current of a few mA in the very beginning and than the current seems to be 0 mA. This cannot be correct. The voltage line does look real to me.
So what do I have to do in the simulation schematic in order to measure the current flowing through D1.
I’ll go try out some things. See if it is any other plot in the right side menu. I see references to D1.
And I go examine the post of @BlackCoffee
Kind regards
Bas