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Installing and using LTspice IV (now including LTXVII). From beginner to advanced.
Installing and using LTspice IV (now including LTXVII). From beginner to advanced.
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Old 24th August 2018, 02:03 PM   #1451
padamiecki is offline padamiecki  Poland
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Quote:
Originally Posted by padamiecki View Post
I cannot check the current placing the cursor over the resistor after the sim, it appears big palm instead of dcm
I do not know how but reading the current placing the cursor over the part works now, sorry for inconvinience
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regards, Pawel
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Old 22nd September 2018, 02:31 PM   #1452
Mooly is offline Mooly  United Kingdom
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Installing and using LTspice IV (now including LTXVII). From beginner to advanced.
I've been having a bit of a tussle with LT in the past week or two in getting a simple 'relay' based circuit to operate correctly.

This all started as an attempt to come up with a simple circuit to make the popular ACA over in the Pass Labs forum silent at power on and power off. I've tried solid state relays and latterly the voltage controlled switch included in LT to operate as a 'short' across the speaker.

Question...

I hit the same problem in all variations and that is that the supposedly closed (contacts normally closed in this version) relay allows the switch OFF thump through.

Is it because the simulated switch relies on a supply voltage being present ?

Here is the simulation (all default LT XVII models) of the amplifier. The speaker is R13 and the input voltage to the amp is removed.

Why does this turn off pulse always appear when the relay should be shorted ? Monitoring the current in the speaker (R13) shows the effect well.

Exactly the same happens with series connected solid state relays and drive circuitry carefully configured to turn them off before the supply has even dipped by few volts. The drive to the relay is removed well before the pulse appears.

Edit... the second image also shows the supply voltage. You can see how quickly the relay should drop out (and become a short)
Attached Images
File Type: jpg Capture.JPG (213.9 KB, 95 views)
File Type: jpg Capture2.JPG (167.8 KB, 90 views)
Attached Files
File Type: asc ACA1 plus Shorting Speaker Relay Simple Version.asc (5.2 KB, 4 views)
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Old 22nd September 2018, 03:35 PM   #1453
Hans Polak is offline Hans Polak  Netherlands
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Had a Quick look.
Change Vh and Vt to 5v and 3v instead of 0v and 6v.

Hans
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Old 22nd September 2018, 05:50 PM   #1454
Mooly is offline Mooly  United Kingdom
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Installing and using LTspice IV (now including LTXVII). From beginner to advanced.
Thanks for looking Hans

Hmm... so changing those parameters seems to mute the audio all the time (if R11 at the left is reconnected).

This is the ACA with audio applied. I can't reason out why the relay doesn't short the audio when its drive is removed.

Also shown is Vh=5 and Vt=3 (and vice versa... it gets confusing)
Attached Images
File Type: jpg Capture3.JPG (216.4 KB, 71 views)
File Type: jpg Capture4.JPG (382.1 KB, 72 views)
File Type: jpg Capture5.JPG (225.9 KB, 75 views)
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Old 22nd September 2018, 06:12 PM   #1455
Mooly is offline Mooly  United Kingdom
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Installing and using LTspice IV (now including LTXVII). From beginner to advanced.
I've uncovered something odd I need to prove with the sim. Static control voltages work fine on the relay. Controlling it from a pulse generator didn't seem to work. It behaved almost like a latching relay.

Thinking out loud now... I need to just quietly try this.
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Old 22nd September 2018, 06:24 PM   #1456
Mooly is offline Mooly  United Kingdom
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Installing and using LTspice IV (now including LTXVII). From beginner to advanced.
Static control voltage works. Proved. Zero control volts to the switch mutes the audio, 24 volts on the switch unmutes it. That is shown in the first two images.

Third image shows the control voltage falling to zero from its initial 24 volts but the switch stays open.
Attached Images
File Type: jpg POC1.jpg (367.5 KB, 8 views)
File Type: jpg POC2.jpg (363.7 KB, 4 views)
File Type: jpg POC3.jpg (389.5 KB, 4 views)
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Old 22nd September 2018, 06:26 PM   #1457
Hans Polak is offline Hans Polak  Netherlands
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Try Vt=5v and Vh=1v
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File Type: jpg Untitled-1.jpg (365.9 KB, 13 views)
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Old 22nd September 2018, 06:31 PM   #1458
Mooly is offline Mooly  United Kingdom
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Installing and using LTspice IV (now including LTXVII). From beginner to advanced.
Ah ! Now that looks good. Thanks very much for that, I'll have to go and think about why that works now.
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File Type: jpg Capture6.JPG (217.3 KB, 11 views)
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Old 22nd September 2018, 08:06 PM   #1459
Mooly is offline Mooly  United Kingdom
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Installing and using LTspice IV (now including LTXVII). From beginner to advanced.
Final one for today.

Simple voltage source and shorting relay. The relay is open when the simulation is first run and is not controlled by V2 (and to me it should be).

If you make V2 a constant 24 volts DC the circuit is unmuted. Make it 0 volts and it mutes. So the relay works with static voltages applied. Set V2 back to a pulse and it doesn't.

Don't understand Why does the dynamically changing control voltage not operate the relay ?
Attached Images
File Type: jpg RT1.JPG (266.0 KB, 13 views)
Attached Files
File Type: asc Relay Test.asc (1,017 Bytes, 0 views)
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Old 23rd September 2018, 01:31 AM   #1460
PaulBysouth is offline PaulBysouth  Australia
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Default Spice Switches

Mooly,
Getting LTspice switches to work is confusing, and the next time you want to use one you forget how to do it. I built subcircuits and symbols to solve this problem.

See attached zip file of a normally open switch and a normally closed switch.

Use as per the attached test circuit. I use the old LTspice, but I expect they will work with the new version. The *.sub files go in the 1sub' directory, and I put the symbols in the `Misc' directory under `sym'.

Regards,
Paul Bysouth
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File Type: jpg Switch_Test.jpg (168.8 KB, 22 views)
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File Type: zip Switch_NO_NC.zip (147.4 KB, 5 views)
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