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LTspice question: modelling a solenoid

P

Phil Allison

"John Nagle"
I need to model the "selector magnet" of a Model 15 Teletype.
This is an electromagnet with an iron core.
DC resistance is 55 ohms. Inductance is 4 Henries.
Click to expand...

** How did yo get that 4H figure??

Iron core solenoids are not pure inductors - they are "lossy inductors"
with phase angles of about 45 degrees.



.... Phil
 
J

John Nagle

I need to model the "selector magnet" of a Model 15 Teletype.
This is an electromagnet with an iron core.
DC resistance is 55 ohms. Inductance is 4 Henries.
Normal operating current is 60mA continuous, but because of the
huge inductance, the normal power source is 120VDC fed through a 2K resistor.

How do I divide up the resistance between the SPICE "series resistance"
and "parallel resistance"? Any ideas?

John Nagle
 
B

[email protected]

   I need to model the "selector magnet" of a Model 15 Teletype.
This is an electromagnet with an iron core.
DC resistance is 55 ohms.  Inductance is 4 Henries.
Normal operating current is 60mA continuous, but because of the
huge inductance, the normal power source is 120VDC fed through a 2K resistor.

   How do I divide up the resistance between the SPICE "series resistance"
and "parallel resistance"?  Any ideas?
Click to expand...

The 55 ohms is most likely just the series resistance of the coil;
pure series resistance.

The parallel resistance is the resistance of the core to induced
current circulating in the core. Working out how big it is presumably
involves measuring the complex impedance of the coil over a range of
frequencies.

You will also have to take into account the parallel capacitance of
the coil, so it is a complicated task.
 
J

Jim Thompson

I need to model the "selector magnet" of a Model 15 Teletype.
This is an electromagnet with an iron core.
DC resistance is 55 ohms. Inductance is 4 Henries.
Normal operating current is 60mA continuous, but because of the
huge inductance, the normal power source is 120VDC fed through a 2K resistor.

How do I divide up the resistance between the SPICE "series resistance"
and "parallel resistance"? Any ideas?

John Nagle
Click to expand...

Unless it's resonant frequency is near the operating conditions,
"lump-lump" should be adequate.

Beware that the inductance of a solenoid can vary quite a bit with
core position.

Is this related to the problem posed a while back about a driver that
was more efficient than a brute force power supply?

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Buy a Fiarysler with your tax credit...
Ignore that grinding noise, that is normal :)
 
J

Jim Thompson

Go on.
Click to expand...

Series resistance only plus the inductance. I've only found a need
for a parallel component, when near electrical resonance, to model the
"Q".
Here the core is stationary, and attracts a flat plate to the ends
of the coils. It's really an electromagnet, not a solenoid with a moving
slug.
Click to expand...

Measure the inductance as the "flat plate" moves. You can calculate
force from that measurement ;-)
Yes. I have a design now. It looks like it's possible to generate
the needed 120VDC 60mA from 5V at 250mA. (The high voltage is only needed
to get a fast rise time despite that big inductance. After the first 2ms
or so, only 3.3V is needed to push 60mA through the 55 ohm coil.) The design
uses a Linear LT3484-1 photoflash charger IC (a little switching power
supply) and a pulse transformer to charge up a 1uF cap
to 120VDC during "off" periods. When the input signal turns on,
the cap is discharged into the coil to pull it in. Then the 3.3V regulator
provides holding current for the remainder of the "on" cycle.

LTspice model below. The key nets to plot are "serialin", "Selector" (the
selector magnet voltage) and current through L3.

The circuit seems to better snubbing at the selector magnet, to dump the
energy when the magnet is turned off. But I'm holding off on that until
the model is realistic. For a real magnet, the R/C snubber shown is sufficient.

John Nagle

Version 4
SHEET 1 1784 680
WIRE -64 -336 -128 -336
WIRE 528 -336 0 -336
WIRE 768 -336 608 -336
WIRE 160 -304 0 -304
WIRE 720 -304 640 -304
WIRE 768 -304 768 -336
WIRE 160 -288 160 -304
WIRE 640 -256 640 -304
WIRE 832 -256 784 -256
WIRE -80 -176 -240 -176
WIRE 0 -176 0 -304
WIRE 0 -176 -80 -176
WIRE 32 -176 0 -176
WIRE 352 -176 288 -176
WIRE 416 -176 416 -208
WIRE 416 -176 352 -176
WIRE 640 -176 416 -176
WIRE 704 -176 704 -256
WIRE -80 -80 -80 -112
WIRE 352 -80 352 -112
WIRE 832 -64 832 -256
WIRE 896 -64 832 -64
WIRE 1008 -64 896 -64
WIRE 896 -48 896 -64
WIRE 160 -32 160 -64
WIRE -240 0 -240 -176
WIRE -64 0 -240 0
WIRE 0 0 -64 0
WIRE 96 0 0 0
WIRE 224 0 96 0
WIRE 384 0 224 0
WIRE 1008 0 1008 -64
WIRE -240 16 -240 0
WIRE 0 16 0 0
WIRE 496 16 432 16
WIRE 592 16 592 -32
WIRE 592 16 560 16
WIRE 640 16 592 16
WIRE 704 16 704 -176
WIRE -240 32 -240 16
WIRE 96 48 96 0
WIRE 224 48 224 0
WIRE 896 48 896 16
WIRE 384 80 384 0
WIRE 432 80 432 16
WIRE 592 80 592 16
WIRE -64 96 -64 64
WIRE 0 112 0 96
WIRE 48 112 0 112
WIRE -240 160 -240 96
WIRE 384 160 272 160
WIRE 592 160 592 144
WIRE 592 160 432 160
WIRE 896 160 896 128
WIRE 896 160 592 160
WIRE 1008 160 1008 80
WIRE 1008 160 896 160
WIRE -128 208 -128 -336
WIRE -128 208 -304 208
WIRE 48 208 -128 208
WIRE 592 208 592 160
WIRE 160 304 160 272
WIRE -304 336 -304 288
FLAG 160 304 0
FLAG -240 160 0
FLAG 592 208 0
FLAG -64 96 0
FLAG -304 336 0
FLAG -240 -176 Vcc
FLAG 640 -256 0
FLAG 1008 -64 Selector
FLAG 592 -32 Pulse120V
FLAG -304 208 serialin
FLAG 352 -80 0
FLAG -80 -80 0
FLAG 240 -32 0
FLAG 416 -208 Continuous3.3V
SYMBOL ind2 368 64 R0
WINDOW 0 -49 34 Left 0
WINDOW 3 -52 75 Left 0
SYMATTR InstName L1
SYMATTR Value 17µ
SYMATTR Type ind
SYMATTR SpiceLine Ipk=0.5 Rser=2.1
SYMBOL ind2 448 176 R180
WINDOW 0 -47 76 Left 0
WINDOW 3 -64 43 Left 0
SYMATTR InstName L2
SYMATTR Value 247µ
SYMATTR Type ind
SYMATTR SpiceLine Rser=0.7
SYMBOL voltage -240 0 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 132 Left 0
SYMATTR SpiceLine Rser=5
SYMATTR InstName V1
SYMATTR Value 4.75
SYMBOL diode 496 32 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D1
SYMBOL cap 576 80 R0
WINDOW 0 43 31 Left 0
SYMATTR InstName C2
SYMATTR Value 1µF
SYMBOL res -16 0 R0
SYMATTR InstName R1
SYMATTR Value 100K
SYMBOL cap -80 0 R0
SYMATTR InstName C1
SYMATTR Value 22µf
SYMBOL voltage -304 192 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 -166 114 Left 0
SYMATTR InstName V2
SYMATTR Value PULSE(0 5 5ms 100us 100us 13.2ms 26.6ms 99)
SYMBOL PowerProducts\\LT3484-1 160 160 R0
SYMATTR InstName U1
SYMBOL res 512 -320 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R2
SYMATTR Value 500
SYMBOL Digital\\inv -64 -400 R0
WINDOW 0 -47 67 Left 0
WINDOW 39 -47 95 Left 0
SYMATTR InstName A1
SYMATTR SpiceLine Vhigh=5
SYMBOL ind 992 -16 R0
SYMATTR InstName L3
SYMATTR Value 4H
SYMATTR SpiceLine Rser=55 Rpar=10000
SYMBOL sw 688 -256 M90
WINDOW 0 -23 94 VRight 0
WINDOW 3 -53 175 VLeft 0
SYMATTR InstName S1
SYMATTR Value hvopto
SYMBOL diode 640 32 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D3
SYMBOL diode 640 -160 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D4
SYMBOL cap 880 -48 R0
SYMATTR InstName C3
SYMATTR Value 1000pf
SYMBOL res 880 32 R0
SYMATTR InstName R3
SYMATTR Value 100
SYMBOL PowerProducts\\LT3080 160 -176 R0
WINDOW 0 -59 -46 Center 0
SYMATTR InstName U2
SYMBOL cap -96 -176 R0
SYMATTR InstName C4
SYMATTR Value 1µf
SYMBOL cap 336 -176 R0
SYMATTR InstName C5
SYMATTR Value 2.2µf
SYMBOL res 144 -16 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R4
SYMATTR Value 330K
TEXT 344 184 Left 0 !K1 L1 L2 0.98
TEXT -168 360 Left 0 !.tran 60m startup
TEXT 288 328 Left 0 ;60mA Teletype power supply design test.\nPRELIMINARY\nJ.
Nagle ([email protected])\nMay 2009
TEXT 336 208 Left 0 ;Pulse PA1546NL
TEXT 640 -368 Left 0 ;Simulated ideal optoisolator
TEXT 536 -400 Left 0 !.model hvopto SW(Ron=4.25 Roff=1Meg Vt=2.0)
Click to expand...

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Stormy on the East Coast today... due to Bush's failed policies.
 
J

John Nagle

Jim said:
Unless it's resonant frequency is near the operating conditions,
"lump-lump" should be adequate.
Click to expand...

Go on.
Beware that the inductance of a solenoid can vary quite a bit with
core position.
Click to expand...

Here the core is stationary, and attracts a flat plate to the ends
of the coils. It's really an electromagnet, not a solenoid with a moving
slug.
Is this related to the problem posed a while back about a driver that
was more efficient than a brute force power supply?
Click to expand...

Yes. I have a design now. It looks like it's possible to generate
the needed 120VDC 60mA from 5V at 250mA. (The high voltage is only needed
to get a fast rise time despite that big inductance. After the first 2ms
or so, only 3.3V is needed to push 60mA through the 55 ohm coil.) The design
uses a Linear LT3484-1 photoflash charger IC (a little switching power
supply) and a pulse transformer to charge up a 1uF cap
to 120VDC during "off" periods. When the input signal turns on,
the cap is discharged into the coil to pull it in. Then the 3.3V regulator
provides holding current for the remainder of the "on" cycle.

LTspice model below. The key nets to plot are "serialin", "Selector" (the
selector magnet voltage) and current through L3.

The circuit seems to better snubbing at the selector magnet, to dump the
energy when the magnet is turned off. But I'm holding off on that until
the model is realistic. For a real magnet, the R/C snubber shown is sufficient.

John Nagle

Version 4
SHEET 1 1784 680
WIRE -64 -336 -128 -336
WIRE 528 -336 0 -336
WIRE 768 -336 608 -336
WIRE 160 -304 0 -304
WIRE 720 -304 640 -304
WIRE 768 -304 768 -336
WIRE 160 -288 160 -304
WIRE 640 -256 640 -304
WIRE 832 -256 784 -256
WIRE -80 -176 -240 -176
WIRE 0 -176 0 -304
WIRE 0 -176 -80 -176
WIRE 32 -176 0 -176
WIRE 352 -176 288 -176
WIRE 416 -176 416 -208
WIRE 416 -176 352 -176
WIRE 640 -176 416 -176
WIRE 704 -176 704 -256
WIRE -80 -80 -80 -112
WIRE 352 -80 352 -112
WIRE 832 -64 832 -256
WIRE 896 -64 832 -64
WIRE 1008 -64 896 -64
WIRE 896 -48 896 -64
WIRE 160 -32 160 -64
WIRE -240 0 -240 -176
WIRE -64 0 -240 0
WIRE 0 0 -64 0
WIRE 96 0 0 0
WIRE 224 0 96 0
WIRE 384 0 224 0
WIRE 1008 0 1008 -64
WIRE -240 16 -240 0
WIRE 0 16 0 0
WIRE 496 16 432 16
WIRE 592 16 592 -32
WIRE 592 16 560 16
WIRE 640 16 592 16
WIRE 704 16 704 -176
WIRE -240 32 -240 16
WIRE 96 48 96 0
WIRE 224 48 224 0
WIRE 896 48 896 16
WIRE 384 80 384 0
WIRE 432 80 432 16
WIRE 592 80 592 16
WIRE -64 96 -64 64
WIRE 0 112 0 96
WIRE 48 112 0 112
WIRE -240 160 -240 96
WIRE 384 160 272 160
WIRE 592 160 592 144
WIRE 592 160 432 160
WIRE 896 160 896 128
WIRE 896 160 592 160
WIRE 1008 160 1008 80
WIRE 1008 160 896 160
WIRE -128 208 -128 -336
WIRE -128 208 -304 208
WIRE 48 208 -128 208
WIRE 592 208 592 160
WIRE 160 304 160 272
WIRE -304 336 -304 288
FLAG 160 304 0
FLAG -240 160 0
FLAG 592 208 0
FLAG -64 96 0
FLAG -304 336 0
FLAG -240 -176 Vcc
FLAG 640 -256 0
FLAG 1008 -64 Selector
FLAG 592 -32 Pulse120V
FLAG -304 208 serialin
FLAG 352 -80 0
FLAG -80 -80 0
FLAG 240 -32 0
FLAG 416 -208 Continuous3.3V
SYMBOL ind2 368 64 R0
WINDOW 0 -49 34 Left 0
WINDOW 3 -52 75 Left 0
SYMATTR InstName L1
SYMATTR Value 17µ
SYMATTR Type ind
SYMATTR SpiceLine Ipk=0.5 Rser=2.1
SYMBOL ind2 448 176 R180
WINDOW 0 -47 76 Left 0
WINDOW 3 -64 43 Left 0
SYMATTR InstName L2
SYMATTR Value 247µ
SYMATTR Type ind
SYMATTR SpiceLine Rser=0.7
SYMBOL voltage -240 0 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 132 Left 0
SYMATTR SpiceLine Rser=5
SYMATTR InstName V1
SYMATTR Value 4.75
SYMBOL diode 496 32 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D1
SYMBOL cap 576 80 R0
WINDOW 0 43 31 Left 0
SYMATTR InstName C2
SYMATTR Value 1µF
SYMBOL res -16 0 R0
SYMATTR InstName R1
SYMATTR Value 100K
SYMBOL cap -80 0 R0
SYMATTR InstName C1
SYMATTR Value 22µf
SYMBOL voltage -304 192 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 -166 114 Left 0
SYMATTR InstName V2
SYMATTR Value PULSE(0 5 5ms 100us 100us 13.2ms 26.6ms 99)
SYMBOL PowerProducts\\LT3484-1 160 160 R0
SYMATTR InstName U1
SYMBOL res 512 -320 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R2
SYMATTR Value 500
SYMBOL Digital\\inv -64 -400 R0
WINDOW 0 -47 67 Left 0
WINDOW 39 -47 95 Left 0
SYMATTR InstName A1
SYMATTR SpiceLine Vhigh=5
SYMBOL ind 992 -16 R0
SYMATTR InstName L3
SYMATTR Value 4H
SYMATTR SpiceLine Rser=55 Rpar=10000
SYMBOL sw 688 -256 M90
WINDOW 0 -23 94 VRight 0
WINDOW 3 -53 175 VLeft 0
SYMATTR InstName S1
SYMATTR Value hvopto
SYMBOL diode 640 32 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D3
SYMBOL diode 640 -160 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D4
SYMBOL cap 880 -48 R0
SYMATTR InstName C3
SYMATTR Value 1000pf
SYMBOL res 880 32 R0
SYMATTR InstName R3
SYMATTR Value 100
SYMBOL PowerProducts\\LT3080 160 -176 R0
WINDOW 0 -59 -46 Center 0
SYMATTR InstName U2
SYMBOL cap -96 -176 R0
SYMATTR InstName C4
SYMATTR Value 1µf
SYMBOL cap 336 -176 R0
SYMATTR InstName C5
SYMATTR Value 2.2µf
SYMBOL res 144 -16 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R4
SYMATTR Value 330K
TEXT 344 184 Left 0 !K1 L1 L2 0.98
TEXT -168 360 Left 0 !.tran 60m startup
TEXT 288 328 Left 0 ;60mA Teletype power supply design test.\nPRELIMINARY\nJ.
Nagle ([email protected])\nMay 2009
TEXT 336 208 Left 0 ;Pulse PA1546NL
TEXT 640 -368 Left 0 ;Simulated ideal optoisolator
TEXT 536 -400 Left 0 !.model hvopto SW(Ron=4.25 Roff=1Meg Vt=2.0)
 
J

Jim Thompson

Go on.

Here the core is stationary, and attracts a flat plate to the ends
of the coils. It's really an electromagnet, not a solenoid with a moving
slug.


Yes. I have a design now. It looks like it's possible to generate
the needed 120VDC 60mA from 5V at 250mA. (The high voltage is only needed
to get a fast rise time despite that big inductance. After the first 2ms
or so, only 3.3V is needed to push 60mA through the 55 ohm coil.) The design
uses a Linear LT3484-1 photoflash charger IC (a little switching power
supply) and a pulse transformer to charge up a 1uF cap
to 120VDC during "off" periods. When the input signal turns on,
the cap is discharged into the coil to pull it in. Then the 3.3V regulator
provides holding current for the remainder of the "on" cycle.

LTspice model below. The key nets to plot are "serialin", "Selector" (the
selector magnet voltage) and current through L3.

The circuit seems to better snubbing at the selector magnet, to dump the
energy when the magnet is turned off. But I'm holding off on that until
the model is realistic. For a real magnet, the R/C snubber shown is sufficient.

John Nagle

Version 4
SHEET 1 1784 680
WIRE -64 -336 -128 -336
WIRE 528 -336 0 -336
WIRE 768 -336 608 -336
WIRE 160 -304 0 -304
WIRE 720 -304 640 -304
WIRE 768 -304 768 -336
WIRE 160 -288 160 -304
WIRE 640 -256 640 -304
WIRE 832 -256 784 -256
WIRE -80 -176 -240 -176
WIRE 0 -176 0 -304
WIRE 0 -176 -80 -176
WIRE 32 -176 0 -176
WIRE 352 -176 288 -176
WIRE 416 -176 416 -208
WIRE 416 -176 352 -176
WIRE 640 -176 416 -176
WIRE 704 -176 704 -256
WIRE -80 -80 -80 -112
WIRE 352 -80 352 -112
WIRE 832 -64 832 -256
WIRE 896 -64 832 -64
WIRE 1008 -64 896 -64
WIRE 896 -48 896 -64
WIRE 160 -32 160 -64
WIRE -240 0 -240 -176
WIRE -64 0 -240 0
WIRE 0 0 -64 0
WIRE 96 0 0 0
WIRE 224 0 96 0
WIRE 384 0 224 0
WIRE 1008 0 1008 -64
WIRE -240 16 -240 0
WIRE 0 16 0 0
WIRE 496 16 432 16
WIRE 592 16 592 -32
WIRE 592 16 560 16
WIRE 640 16 592 16
WIRE 704 16 704 -176
WIRE -240 32 -240 16
WIRE 96 48 96 0
WIRE 224 48 224 0
WIRE 896 48 896 16
WIRE 384 80 384 0
WIRE 432 80 432 16
WIRE 592 80 592 16
WIRE -64 96 -64 64
WIRE 0 112 0 96
WIRE 48 112 0 112
WIRE -240 160 -240 96
WIRE 384 160 272 160
WIRE 592 160 592 144
WIRE 592 160 432 160
WIRE 896 160 896 128
WIRE 896 160 592 160
WIRE 1008 160 1008 80
WIRE 1008 160 896 160
WIRE -128 208 -128 -336
WIRE -128 208 -304 208
WIRE 48 208 -128 208
WIRE 592 208 592 160
WIRE 160 304 160 272
WIRE -304 336 -304 288
FLAG 160 304 0
FLAG -240 160 0
FLAG 592 208 0
FLAG -64 96 0
FLAG -304 336 0
FLAG -240 -176 Vcc
FLAG 640 -256 0
FLAG 1008 -64 Selector
FLAG 592 -32 Pulse120V
FLAG -304 208 serialin
FLAG 352 -80 0
FLAG -80 -80 0
FLAG 240 -32 0
FLAG 416 -208 Continuous3.3V
SYMBOL ind2 368 64 R0
WINDOW 0 -49 34 Left 0
WINDOW 3 -52 75 Left 0
SYMATTR InstName L1
SYMATTR Value 17µ
SYMATTR Type ind
SYMATTR SpiceLine Ipk=0.5 Rser=2.1
SYMBOL ind2 448 176 R180
WINDOW 0 -47 76 Left 0
WINDOW 3 -64 43 Left 0
SYMATTR InstName L2
SYMATTR Value 247µ
SYMATTR Type ind
SYMATTR SpiceLine Rser=0.7
SYMBOL voltage -240 0 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 132 Left 0
SYMATTR SpiceLine Rser=5
SYMATTR InstName V1
SYMATTR Value 4.75
SYMBOL diode 496 32 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D1
SYMBOL cap 576 80 R0
WINDOW 0 43 31 Left 0
SYMATTR InstName C2
SYMATTR Value 1µF
SYMBOL res -16 0 R0
SYMATTR InstName R1
SYMATTR Value 100K
SYMBOL cap -80 0 R0
SYMATTR InstName C1
SYMATTR Value 22µf
SYMBOL voltage -304 192 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 -166 114 Left 0
SYMATTR InstName V2
SYMATTR Value PULSE(0 5 5ms 100us 100us 13.2ms 26.6ms 99)
SYMBOL PowerProducts\\LT3484-1 160 160 R0
SYMATTR InstName U1
SYMBOL res 512 -320 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R2
SYMATTR Value 500
SYMBOL Digital\\inv -64 -400 R0
WINDOW 0 -47 67 Left 0
WINDOW 39 -47 95 Left 0
SYMATTR InstName A1
SYMATTR SpiceLine Vhigh=5
SYMBOL ind 992 -16 R0
SYMATTR InstName L3
SYMATTR Value 4H
SYMATTR SpiceLine Rser=55 Rpar=10000
SYMBOL sw 688 -256 M90
WINDOW 0 -23 94 VRight 0
WINDOW 3 -53 175 VLeft 0
SYMATTR InstName S1
SYMATTR Value hvopto
SYMBOL diode 640 32 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D3
SYMBOL diode 640 -160 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D4
SYMBOL cap 880 -48 R0
SYMATTR InstName C3
SYMATTR Value 1000pf
SYMBOL res 880 32 R0
SYMATTR InstName R3
SYMATTR Value 100
SYMBOL PowerProducts\\LT3080 160 -176 R0
WINDOW 0 -59 -46 Center 0
SYMATTR InstName U2
SYMBOL cap -96 -176 R0
SYMATTR InstName C4
SYMATTR Value 1µf
SYMBOL cap 336 -176 R0
SYMATTR InstName C5
SYMATTR Value 2.2µf
SYMBOL res 144 -16 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R4
SYMATTR Value 330K
TEXT 344 184 Left 0 !K1 L1 L2 0.98
TEXT -168 360 Left 0 !.tran 60m startup
TEXT 288 328 Left 0 ;60mA Teletype power supply design test.\nPRELIMINARY\nJ.
Nagle ([email protected])\nMay 2009
TEXT 336 208 Left 0 ;Pulse PA1546NL
TEXT 640 -368 Left 0 ;Simulated ideal optoisolator
TEXT 536 -400 Left 0 !.model hvopto SW(Ron=4.25 Roff=1Meg Vt=2.0)
Click to expand...

LTspice doesn't like that "\n", though it proceeds anyway.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Stormy on the East Coast today... due to Bush's failed policies.
 
J

Jim Thompson

On Thu, 07 May 2009 13:13:24 -0700, Jim Thompson

[snip]
LTspice doesn't like that "\n", though it proceeds anyway.
Click to expand...

What it's balking at is a wrapped line that occurred during posting.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Stormy on the East Coast today... due to Bush's failed policies.
 
J

Jim Thompson

I need to model the "selector magnet" of a Model 15 Teletype.
This is an electromagnet with an iron core.
DC resistance is 55 ohms. Inductance is 4 Henries.
Normal operating current is 60mA continuous, but because of the
huge inductance, the normal power source is 120VDC fed through a 2K resistor.

How do I divide up the resistance between the SPICE "series resistance"
and "parallel resistance"? Any ideas?

John Nagle
Click to expand...

What does the flyback condition look like with the _real_ solenoid? At
4H I would expect some pretty low frequency "squirrelies" ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Stormy on the East Coast today... due to Bush's failed policies.
 
J

John Nagle

Jim said:
What does the flyback condition look like with the _real_ solenoid? At
4H I would expect some pretty low frequency "squirrelies" ;-)

...Jim Thompson
Click to expand...

The traditional driving circuit is a 120VDC supply fed through
a 2K resistor and keyboard contacts, with no snubbing at all. The contacts
arc visibly and produce noticeable ozone. That's the 1930 technology
in its original form.

My present driving circuit is a 120VDC open-frame supply fed through
a 2K resistor and a high-voltage optoisolator, with a snubber consisting
of a 1pf cap in series with a 100 ohm resistor. This works fine, but
it's a bit bulky.

I'll have to hook up a scope and look at the voltage across
the selector magnet. (After wiring up a voltage divider
to get the voltage down to the scope's range.)

Trying to do this off a 5V supply is mostly an elegance thing.
But I may need to build a USB interface. Most USB to serial
converters won't go down to 45.45 baud. (They should, from the
spec, but in practice the firmware in common use won't go below
110 baud.) I want to run the Teletype from a laptop with USB
ports only, instead of a mini-tower PC with a classic serial port
that will run at 45 baud. So I may have to use an Atmel CPU with
USB software as an interface device. If I do that, it would
be convenient to eliminate the need for the 120VDC supply and
run the whole thing off the USB port.

John Nagle
 
J

Jim Thompson

The traditional driving circuit is a 120VDC supply fed through
a 2K resistor and keyboard contacts, with no snubbing at all. The contacts
arc visibly and produce noticeable ozone. That's the 1930 technology
in its original form.

My present driving circuit is a 120VDC open-frame supply fed through
a 2K resistor and a high-voltage optoisolator, with a snubber consisting
of a 1pf cap in series with a 100 ohm resistor. This works fine, but
it's a bit bulky.

I'll have to hook up a scope and look at the voltage across
the selector magnet. (After wiring up a voltage divider
to get the voltage down to the scope's range.)

Trying to do this off a 5V supply is mostly an elegance thing.
But I may need to build a USB interface. Most USB to serial
converters won't go down to 45.45 baud. (They should, from the
spec, but in practice the firmware in common use won't go below
110 baud.) I want to run the Teletype from a laptop with USB
ports only, instead of a mini-tower PC with a classic serial port
that will run at 45 baud. So I may have to use an Atmel CPU with
USB software as an interface device. If I do that, it would
be convenient to eliminate the need for the 120VDC supply and
run the whole thing off the USB port.

John Nagle
Click to expand...


Here's how I'd attack your problem (in the manner of how I used to
make CD ignition systems)....

http://analog-innovations.com/SED/HammerDriver(J.Nagle).pdf

(Paste to make sure your reader gets the parentheses part).

[1] It is left as an exercise for the student to choose a PowerMOS
replacement for S1... I no longer carry a catalog in my head like I
did in the '80's :)

[2] Also what logic to choose for the driving signal path.

[3] The coil is presently modeled simply as 4H + 55 Ohms. If it were
my project I'd take a network analyzer to the coil. I'd also measure
inductance versus current, and create an accurate Spice model... I
suspect that the real world will be full of ring-a-ding-dings ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Stormy on the East Coast today... due to Bush's failed policies.
 
J

Jim Thompson

I need to model the "selector magnet" of a Model 15 Teletype.
This is an electromagnet with an iron core.
DC resistance is 55 ohms. Inductance is 4 Henries.
Normal operating current is 60mA continuous, but because of the
huge inductance, the normal power source is 120VDC fed through a 2K resistor.

How do I divide up the resistance between the SPICE "series resistance"
and "parallel resistance"? Any ideas?

John Nagle
Click to expand...

Now at device level (no behavioral)....

http://analog-innovations.com/SED/HammerDriver(J.Nagle)2.pdf

(Paste to make sure your reader gets the parentheses part).

11mW dissipation in the MOSFET ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

If I'm talking, you should be taking notes.
 
F

Fred Abse

Now at device level (no behavioral)....

http://analog-innovations.com/SED/HammerDriver(J.Nagle)2.pdf
Click to expand...

There's a problem with this, Jim. Your circuit works fine with a
continuous pulse train, but teletype isn't like that, it can have long
periods of no activity (constant Mark signal), then a few characters, then
more inactivity. The selector magnet must respond to the first drop to
Space (beginning of start bit) of the first character.

The idle state is constant Mark (positive or 0V, depending on whether it's
polar or neutral signaling).

John's approach does take account of this.
 
F

Fred Abse

The circuit seems to better snubbing at the selector magnet, to dump
the
energy when the magnet is turned off. But I'm holding off on that until
the model is realistic. For a real magnet, the R/C snubber shown is
sufficient.
Click to expand...

Running a simulation here, I get a massive (400V plus) negative spike at
the coil on turnoff. I'd suggest replacing the RC snubber with a diode and
a 2k resistor, which will give the same falling time constant as the
original 120V "brute force" circuit, and reduce the -ve spike to around
-80V.

BTW, is there any reason for running your simulation at 75.75 baud, rather
than the 45.45 you said you would be running the machine at?
 
J

Jim Thompson

There's a problem with this, Jim. Your circuit works fine with a
continuous pulse train, but teletype isn't like that, it can have long
periods of no activity (constant Mark signal), then a few characters, then
more inactivity. The selector magnet must respond to the first drop to
Space (beginning of start bit) of the first character.

The idle state is constant Mark (positive or 0V, depending on whether it's
polar or neutral signaling).

John's approach does take account of this.
Click to expand...

If "Mark" is current in the solenoid, it's fine. (I'm obviously not
at all familiar with Teletype... I'm not THAT old ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Stormy on the East Coast today... due to Bush's failed policies.
 
F

Fred Abse

If "Mark" is current in the solenoid, it's fine.
Click to expand...

On a neutral (current or no current) system, mark is no current.
Makes idling more economical.
 
J

Jim Thompson

On a neutral (current or no current) system, mark is no current.
Makes idling more economical.
Click to expand...

Could the first "space" be made long?

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Stormy on the East Coast today... due to Bush's failed policies.
 
F

Fred Abse

Could the first "space" be made long?
Click to expand...

The first space is the start bit from which the sample timing originates.
It's the usual start/stop protocol: One start bit, five NRZ data bits, 1.5
stop bits. The start bit trips the clutch that starts the reading
mechanism, which samples the position of the selector magnet at fixed
intervals. The mechanism resets after 5 bit intervals and the clutch
disengages. You can regard the idle condition as one long continuous stop
signal, it's actually only 1.5 bit intervals between successive characters
in a string.

Most machines have an adjustment to set the sampling window relative to
the start so as to get the sample on the flat part of the pulses.

I once had a teletype as printer for a TRS-80 (remember those?), using the
cassette motor relay for signaling. I think I've still got the Z80
assembly code somewhere.
 
F

Fred Abse

Punched tapes could reliably achieve this tightness of character
separation. Manual typists had much more jitter in start to start. The
system is truly asynchronous between characters. Intra character timing
was created by steady speed electromechanical means.
Click to expand...

Most machines needed either CR-CR-LF or LF-CR-CR as end-of-line, adding a
delay, to allow the carriage or basket to fully return, otherwise you got
the first character of the next line printing whilst the carriage was
still flying.

That's the reason for the still-widespread CNC tape code using LF-CR-CR.
It was designed for ASR33s et al.

When all the "modern" magnetic and semiconductor media have lost data,
punched paper tape will still be readable, by humans if necessary.
 
J

Jim Thompson

The first space is the start bit from which the sample timing originates.
It's the usual start/stop protocol: One start bit, five NRZ data bits, 1.5
stop bits. The start bit trips the clutch that starts the reading
mechanism, which samples the position of the selector magnet at fixed
intervals. The mechanism resets after 5 bit intervals and the clutch
disengages. You can regard the idle condition as one long continuous stop
signal, it's actually only 1.5 bit intervals between successive characters
in a string.

Most machines have an adjustment to set the sampling window relative to
the start so as to get the sample on the flat part of the pulses.

I once had a teletype as printer for a TRS-80 (remember those?), using the
cassette motor relay for signaling. I think I've still got the Z80
assembly code somewhere.
Click to expand...

So make a 120V supply that can supply just the "leak-off", then the
"snub" energy won't go to waste and heat.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Stormy on the East Coast today... due to Bush's failed policies.
 
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