Variation on the 5v -> 12v newbie question...

[Jonathan Kirwan]

The time has come for that, IMHO.

I have a set of them, by now. But I can include the one that is based
on your schematic (uses the Zetex model and a 10 ohm, 200mH relay) as
a starting point. Would that be okay? (See bottom of post.)

"Criterion" means some rule for deciding something.
What I'm asking is: How do you decide where to place
those cursors before you read off their time difference?
In another post, I mentioned the 99% to 37% fall time
and the 1% to 63% rise time. The criteria for how one
would measure those are evident. (I suppose I should
mention that they relate to current changes, not voltage.)
Your criteria remain a complete mystery. What precisely
happens between the start of your "rise time" and the end
of it? Repeat the question for your "decay time".

I used the same measuring rules for both directions. I will leave it
to you to look at when you load up the LTSpice schematic. I think you
will be able to see that the fall time is at least ... longer ...
regardless of your standard chosen.

Ok, I misunderstood you.

No problem. It seemed that way, which is why I posted a more detailed
description of my thinking.

Jon

P.S. Note that the last two TEXT lines describe the two models I
included, one for the diode, the other for the PNP transistor. I'm
not sure how my email posting program will wrap these lines versus how
LTSpice wants them. But you should be able to edit them in,
correctly, with only a small bother at most.



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[Larry Brasfield]

I have a set of them, by now. But I can include the one that is based
on your schematic (uses the Zetex model and a 10 ohm, 200mH relay) as
a starting point. Would that be okay? (See bottom of post.)

Sure, if it works.

I used the same measuring rules for both directions.

You appear determined to be mysterious about them.

I will leave it
to you to look at when you load up the LTSpice schematic. I think you
will be able to see that the fall time is at least ... longer ...
regardless of your standard chosen.

(LTSpice schematic and related notes cut.)

I ran your simulation with these results:
current rise time 0% to 90% = 44.25 mS
current fall time 100% to 10% = 36.33 mS
current rise time 1% to 63% = 19.21 mS
current fall time 99% to 37% = 17.35 mS
(The cycle time is not adequate to let the on current
settle to the steady state, being only about 10 L/R.
This has reduced the expected 1% to 63% rise time
from the expected 19.8 mS to the value seen above.)
To me, it appears that the fall time is uniformly shorter.
I will leave it to you to figure out why your method for
measuring rise and fall time leads to inexplicable results.

 

[Jonathan Kirwan]

<snip of other material, until later>
(LTSpice schematic and related notes cut.)

I ran your simulation with these results:
current rise time 0% to 90% = 44.25 mS
current fall time 100% to 10% = 36.33 mS
current rise time 1% to 63% = 19.21 mS
current fall time 99% to 37% = 17.35 mS
(The cycle time is not adequate to let the on current
settle to the steady state, being only about 10 L/R.
This has reduced the expected 1% to 63% rise time
from the expected 19.8 mS to the value seen above.)
To me, it appears that the fall time is uniformly shorter.
I will leave it to you to figure out why your method for
measuring rise and fall time leads to inexplicable results.

To the issue mentioned above, looking at the curve for I(L1), at about
0.2s on my .tran display, I see it just start to rise. (You are right
about not providing enough time, but I don't think this is material to
the discussion. It does rise to about 1.17A and must ramp down from
that point and is able to completely go back to zero, so the situation
should still be worth discussing.) I used your figure of 63% from the
earlier post and this is about .737A. I get about 19.72ms for the
time, as close as I can make it out zooming out the display. At 0.3s,
the solenoid looses its supply and the current ramps down. 37% is
..433A. I see this take place 18.1ms later. Looking back over my
notes, I see where I'd confused two pairs of numbers taken with
different values for the solenoid. My mistake! Thanks.

I'm curious to see if you found the oscillation in the simulation and
might address yourself to that.

Jon

 

[Larry Brasfield]

(I, Brasfield, did not write the above line.)
....

To the issue mentioned above, looking at the curve for I(L1), at about
0.2s on my .tran display, I see it just start to rise. (You are right
about not providing enough time, but I don't think this is material to
the discussion.

It is only material in that it explains the deviation in rise time
from what would be predicted using the component values.

[snip]

I'm curious to see if you found the oscillation in the simulation and
might address yourself to that.

My first post in this thread on June 26 addressed that.
With the addition of a few elements to simulate the effect
of eddy current losses in the solenoid magnetic structure,
your simulation shows behavior at diode turn-off that is
much closer to what can be observed with real solenoids.

In this simulation, (included below), there is a small amount
of ringing, barely visible without zooming in on it. Without
considerably more work, I cannot be sure that those added
elements accurately model the layered single turns of steel
that are present in most real solenoids, acting as parasitic
secondaries that absorb energy at higher frequencies. To
get that close would require looking at some actual parts.

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[west]

Yes, The transistor needs to be PNP (NTE12), because the solenoids are
grounded. And you need another NPN like 2N3906 to make a level translator.

12V PNP
o-----o------ -----------o
| \ v |
| --- |
| ___ | |
'-|___|-o |
10k | |
.-. |
| |560 |
| |0.5W |
'-' |
| 1N4001 |
INPUT | .---o
___ |/ | |_
o-|___|-o---| NPN - )|
4k7 | |> ^ )|
.-. | | ._)|
| | | '---o
10k| | | |
'-' | ===
| | GND
=== ===
GND GND
(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)
View/font fixed

Hello Ban,
I believe the 3906 is a PNP and the 3904 is the NPN.
Cordially,
west

 

[Ban]

Hello Ban,
I believe the 3906 is a PNP and the 3904 is the NPN.
Cordially,
west

Yes, I always mess them up. Also the drawing is messed up. The emitter of
the PNP should be at the input voltage. ASCII kills me! I use mainly
European part numbers, BC546(NPN) BC556(PNP) or BC337(NPN) and BC327(PNP)
for higher current.