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Old 9th November 2013, 08:01 AM   #11
Mooly is offline Mooly  United Kingdom
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The best guide I have seen for using LTspice is Bob Cordells book "Designing Audio Power Amplifiers". I hadn't a clue how to get started until I read this.

As you have the program installed here is a simple PSU (a voltage doubler) that will get you a started on running and probing circuits. Just unzip the file and put it in docs and either click the file (if a MAC will allow) or open Spice and click file and "open" and browse for it. Click the running man at the top to run it and use the cursor to probe the circuit.

Not sure how it works on a MAC, but if its like Windows then by default the files are stored in amongst the program files. I would advise you to save any simulation files you create in a normal folder like docs etc.

Also, click the "hammer" symbol on the top line and set the following options to automatically delete files (.raw and other files) everytime you close the program.

If you have run a simulation already then search your PC for .raw files and delete them. They can grow to be huge.
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Old 10th November 2013, 08:16 PM   #12
SGK is offline SGK
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Thanks a lot. The Mac version doesn't have any of the toolbars that appear in the Windows version (unless I have done something wrong). This is all you get:

Click the image to open in full size.

I also am a bit daunted by the need to profile every component I add. For example, I can add a capacitor and fill in its capacitance but I have no idea about its series inductance etc. So it's going to be a slow learning curve. Learning how to probe LTSPICE while learning what probing is, how to do it and what to look for is a steep curve.

Thanks for the reference to the book. I read a couple of reviews and the Amazon description. It seems rather daunting for a complete newbie to electronics! I feel like I am having to explore the deep end rather than hopping in at the shallow end and wading deeper.

Can I ask a couple of super basic questions in order to try to get things into a better perspective? When one mentions transformer ringing is this a topic (somewhat) separate from a discussion of filtering AC noise from a DC voltage or is this much the same thing? Is a snubber on the transformer secondary and a CLC filter intended to tackle the same issue? In a basic single voltage power supply such as the challenge I have set myself, is it typical or good to see a CLC filter or would one deal with any transformer ringing at the secondary and then simply run a cap/reg/cap setup such as the one I already have?

I built the "dim bulb tester" this afternoon. I followed the direction given here. At the moment I have a 100W bulb fitted. Thanks again for the safety advice.
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Old 11th November 2013, 07:07 AM   #13
Mooly is offline Mooly  United Kingdom
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I've never even had my mits on a MAC so honestly haven't a clue where you go from here.

For me, Bobs book was a revelation in getting started with simulation because it detailed literally every click needed. No prior knowledge was assumed. When I ordered the book I hoped there wouldn't be to much on simulation... when I started reading it I wished there was more.

Generally we don't add extra info to the standard components such self inductance etc A snubber across the secondary supresses noise and ringing, ringing that can be caused by the diodes in the bridge dropping out of conduction each half cycle.

I think the first step has to be to see if you can get all the LTspice options showing on a MAC.
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Old 12th November 2013, 10:43 AM   #14
SGK is offline SGK
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I bought the book. Even the introductory stuff is way above my knowledge level but I will wade my way through as much as I can! It is interesting to learn.

I have some "best practice" and safety questions regarding installing this transformer. As I am in the UK I need to wire the primaries in series, using the blue and brown and jumpering grey to violet.

When I purchased the transformer I had thought that 2 secondaries of 15V meant that I could use one and tuck the other away for later use. I now see from footnote 1 on the datasheet that this is not the case. In any event, I only need 1 x 12V output for now. So I need to wire the secondaries in parallel - use black and yellow, and jumper black to orange and red to yellow.

For each of the primary (blue and brown) and secondary (black and yellow), which one should be connected to Live and which to Neutral?

What's good practice for the dealing with the wires that need to be jumpered? I presume one cuts them short, solders them and insulates with heatshrink sleeving but want to check. Lastly, if the long primary leads aren't quite long enough to reach the IEC inlet, again, what's best practice? I assume it is best to run a length of good quality, shielded power cable through the enclosure and again cut the existing primary leads short, solder and shield with heatshrink?

Sorry for the basic questions but given this is the first time I am doing this and AC is involved I want to make sure I am doing everything safely.
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Old 12th November 2013, 03:52 PM   #15
SGK is offline SGK
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An obvious typo above: "1 x 15V" not "1 x 12V"
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Old 12th November 2013, 06:03 PM   #16
Mooly is offline Mooly  United Kingdom
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The book will be a great help and Bob has all the examples mentioned in the simulation section on his site ready to download and run in LTspsice.

With the transformer I would still recommend using the bulb tester initially while determining and connecting the windings. The data sheet looks 100% correct but you never know. If you got the phase of a winding wrong the current draw would be immense and the bulb saves all that.

As you have typed... connecting secondaries to L or N NO. The secondary's must NEVER contact the primary.

It looks like you need to connect black to orange and red to yellow to place one winding in parallel with the other.
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Old 12th November 2013, 06:26 PM   #17
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Hi - not what I meant.

I meant for the in-series primary there will be blue and brown to connect to the incoming AC. One of these needs to be connected to the Live of the IEC inlet and one to Neutral on the IEC inlet. Does it matter which way around?

For the parallel-wired secondary (black and orange paired and red and yellow paired) one of these needs to be connected to the diodes at point L on my hand-drawn diagram me (A on the schematic I drew of the full-wave bridge rectifier) and the other at point N. Again, does it matter which one goes to to each?

The descriptions here don't say which way around these 2 pairs are connected.

I will absolutely be using the bulb tester. Don't worry. I'm very glad to have that thing to hopefully reduce risks here!

On the book, yes, I have now skipped to the section on simulation. :-)
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Old 12th November 2013, 06:52 PM   #18
Mooly is offline Mooly  United Kingdom
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Ah.. OK

I would stick to convention and wire brown to live and blue to neutral simply to keep to standard colour schemes but it doesn't matter operationally for a transformer. The same applies to the correctly paralleled secondary. You can wire it either way round to the bridge. There is no difference.
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Old 12th November 2013, 07:12 PM   #19
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Another vote here for LTSpice. I've just scaped the surface for PSU and (tube)amp simulations, but it has already proven itself as a very powerfull tool indeed. The Mac version I'm running (win version wrapped in Wineskin) works exactly the same as in Windows.
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Old 12th November 2013, 09:19 PM   #20
SGK is offline SGK
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Thanks Mooly

Funk1980, have you tried using the Mac version that was released in August?

I'm making some progress with LTSPICE for Mac but it is a little like poking around in the dark - both because of my limited knowledge of electronics and limited knowledge of SPICE. The Mac version doesn't have the toolbars but it seems to all be there. It seems that the equivalent of "Edit Simulation Command" in Windows is just a text editor requiring one to know how the commands/fields end up in the text string.

I've linked to the (very basic) asc file I have so far. I can't figure out a few things, namely:

- the circuit presumably needs some sort of load or Vout representation after C3 (EDIT: I think I have fixed this?)
- I just picked a generic Schottky diode for the bridge diodes. I can't see how to refine this for the Cree diodes I have.
- same thing for the regulator. I don't have the information to model the Fidelity Audio SPower HC regulator (+12V, circa 5V drop)
- I'm not getting the AC voltage I was expecting to measure (15V) nor the level of DC after rectification (I was expecting circa 15 x 1.4 - 2 = 19V)

etc etc

Until I get these basics right it's hard to move forward. I will keep at it.

Last edited by SGK; 12th November 2013 at 09:40 PM.
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