LTX Mag Hold

PLAN: Modify LTX so it cannot be easily turned off once turned on.

The simulation below is currently untested on a real tagger.

Open this link: https://falstad.com/circuit/circuitjs.html

And import the following text:

$ 3 0.000005 17.532943091211475 45 5 50
g 168 592 168 640 0
R 136 528 56 528 0 0 40 4.5 0 0 0.5
S 408 544 312 544 0 0 false 0 2
r 312 560 168 592 0 150
w 136 528 312 528 0
w 408 544 456 544 0
207 456 544 456 496 0 V4.5
r 456 544 552 544 0 10
207 552 544 552 496 0 Vcc
207 792 544 792 496 0 VSW
207 1000 416 1000 368 0 VDRV
207 1208 416 1208 352 0 SW9V
c 552 544 552 624 0 0.00009999999999999999 0.00003248369301036018
g 552 624 552 656 0
w 552 544 632 544 0
r 632 544 632 736 0 100000
w 632 544 696 544 0
t 712 624 712 544 1 -1 -0.21327651471586118 -0.00003069279510278976 100
w 728 544 792 544 0
r 712 624 712 736 0 4700
w 712 736 632 736 0
w 632 736 488 736 0
c 792 544 792 640 0 0.000009999999999999999 0.21327830561376876
g 792 640 792 688 0
w 792 544 936 544 0
r 936 544 936 640 0 100000
g 936 640 936 704 0
r 936 544 1048 544 0 22000
w 1048 544 1048 624 0
t 1048 624 1112 624 0 1 -8.786637036405363 0.21327822397896384 100
g 1112 640 1112 688 0
r 1112 608 1112 480 0 2200
r 1112 480 1000 480 0 220000
t 1112 480 1112 416 1 -1 8.999916096968825 -0.00008390080424014457 100
w 1096 416 1000 416 0
w 1000 416 1000 480 0
207 160 440 160 392 0 VDRV
R 64 440 64 376 0 0 40 9 0 0 0.5
404 64 440 160 440 0 0.0613 6.73 0 false
w 1128 416 1208 416 0
g 1304 592 1304 656 0
r 1304 592 1304 416 0 360
162 1208 416 1304 416 2 default-led 0 1 0 0.02
x 352 791 760 794 4 24 MCU\sholds\s/VSW\sto\sGND\snormally
x 1283 394 1457 397 4 24 LTX\sScope\sSim
x 305 588 417 591 4 16 factory\sswitch
f 456 176 456 248 40 1.5 0.02
R 352 248 248 248 0 0 40 4.5 0 0 0.5
207 528 248 528 296 0 V4.5
w 528 248 472 248 0
w 352 248 440 248 0
207 456 88 456 24 0 SW9V
r 456 88 456 176 0 1000
s 536 176 680 176 0 1 true
w 536 176 456 176 0
g 680 176 680 224 0
x 578 138 826 141 4 24 "reed"hold\sfor\s1/4s\p
g 320 752 320 784 0
S 488 736 392 736 0 0 false 0 2
w 392 752 320 752 0
207 392 720 392 672 0 Vcc
r 456 176 328 176 0 10000
g 328 176 280 176 0

Rev update: 1.01 -- added a path to ground on gate as not sure what path SW9V has elsewhere in circuit without looking closer.

n-MOSFET simulation:

Idle (off):
Ids = 45nA
Vgs = -32.415uV
Vds = 4.5V
gm = 0A/V
P = 202nW
Ib = -171.435nA

Active (factory switch on):
Ids = 0A
Vgs = 3.632V
Vds = 0V
gm = 0 A/V
P = 0W
Ib = 0A

Active (factory switch off / under load):
Ids = 27.179mA
Vgs = 4.195V
Vds = 563.11mV
gm = 11.262mA/V
P = 15.305mW
Ib = -171.432nA

Possible source for the n-MOSFET: https://www.mouser.com/_/?Keyword=BS170-D26Z