Re: Simple inverter switch transistor circuit help needed

J

John Fields 18 years ago

This will work most of the time. It depends on the power supply voltage

>and LED forward voltage drop:
>
> View in a fixed-width font such as Courier.
>
> .
> .
> . /
> . Vcc>----+----o o----+--->
> . | SW | SW closed
> . [R1] |
> . | | V -V
> . | | F EB
> . + - - ------ | *
> . V V D1 V D2 R1 \\ *
> . F - - |\\ *
> . - | | | \\ *
> . | | | \\ *
> . >| | | \\ *
> . |---------+ I ^ | \\ *
> . /| | d | | \\ *
> . | [R2] | \\ *
> . | | +*-*-*-*+*----+--
> . | | V -V V
> . --- --- F EB F
> . V ->
> . d
> .
> .
> .

This will work _all_ the time: . .Vcc>--+----------------+ . | | . | O | . | [R3] . | O | . | | . |A +-----+ . [LED1] | | . | C |A . +--[R2]--B NPN [LED2] . | Q1 E | . [R1] | | . | | | .GND>--+----------+-----+ .

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J

John Fields 18 years ago

P.S. Version 4 SHEET 1 880 680 WIRE -160 96 -432 96 WIRE 80 96 -160 96 WIRE -160 128 -160 96 WIRE -208 144 -336 144 WIRE 80 144 80 96 WIRE -208 192 -240 192 WIRE -160 240 -160 208 WIRE 80 256 80 224 WIRE 176 256 80 256 WIRE -432 288 -432 96 WIRE -336 288 -336 144 WIRE 80 304 80 256 WIRE 176 320 176 256 WIRE -160 352 -160 304 WIRE -96 352 -160 352 WIRE 16 352 -16 352 WIRE -160 384 -160 352 WIRE -432 512 -432 368 WIRE -336 512 -336 368 WIRE -336 512 -432 512 WIRE -240 512 -240 192 WIRE -240 512 -336 512 WIRE -160 512 -160 464 WIRE -160 512 -240 512 WIRE 80 512 80 400 WIRE 80 512 -160 512 WIRE 176 512 176 384 WIRE 176 512 80 512 WIRE -432 592 -432 512 FLAG -432 592 0 SYMBOL res 64 128 R0 SYMATTR InstName R1 SYMATTR Value 150 SYMBOL npn 16 304 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL LED 160 320 R0 SYMATTR InstName D1 SYMATTR Value QTLP690C SYMATTR Description Diode SYMATTR Type diode SYMBOL res 0 336 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R2 SYMATTR Value 2000 SYMBOL voltage -432 272 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 5 SYMBOL voltage -336 272 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 WINDOW 3 24 104 Invisible 0 SYMATTR InstName V2 SYMATTR Value PULSE(0 5 0 1e-6 1e-6 1 2) SYMBOL sw -160 224 M180 WINDOW 0 32 15 Left 0 WINDOW 3 32 44 Left 0 SYMATTR InstName S1 SYMBOL res -176 368 R0 SYMATTR InstName R3 SYMATTR Value 150 SYMBOL LED -176 240 R0 WINDOW 3 87 38 Left 0 SYMATTR InstName D2 SYMATTR Value QTLP690C SYMATTR Description Diode SYMATTR Type diode TEXT -408 536 Left 0 !.model SW SW(Ron=1 Roff=10Meg Vt=0.5Vh=0) TEXT -408 568 Left 0 !.tran 0 10 0

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J

Jonathan Kirwan 18 years ago

Just for grins, I ran that circuit through my LTSpice-to-ASC converter and got this:

Jon

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J

John Fields 18 years ago

WOW! Pretty damn slick!!! :-)

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F

Fred Bloggs 18 years ago

This one is better'n the both of them, your circuit wastes current:

Why don't you verify the equations ( I whipped them out) and construct a design note on how to select R1,2,3 in terms of Vcc, and VF1,2...

View in a fixed-width font such as Courier.

. . . / . Vcc>----+----o o-----+--->

. | SW | . [R1] | . | | Vcc-V -V . | | F1 EB R2+R3 . + - 1N4148| R1 = ----------- - ----- . V V D1 .--|| | | . |--+-[R3]--+ Vcc-V . /| | F2 . | [R2] R2 = --------------- . | | V -0.7 . | | F2 . --- --- I + ------- . F2 R3 .

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J

Jonathan Kirwan 18 years ago

hehe. If you are interested, I can provide a link where you can download it -- with or without source. Like anything done for free, it has its limitations (due to my time.) But I wouldn't mind feedback about what to work on. A little useful focus wuold sharpen the use of what time I can afford to enhance it.

The program is something I whipped up a while back when I decided I thought I'd let LTSpice capture the schematics I post in ASCII. It turned out to actually be easier than I first imagined, but there were a few things I had to learn along the way. Parsing was easy. The key was to imagine an ASCII drawing space and to use "greatest common divisor" means to find the least number of ASCII characters required to replace wires and so on.

Jon

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J

John Fields 18 years ago

Good circuit, but I think I\'ll forego the analysis and tutorial writing. Sounds too much like work that ought to be coming out of _your_ camp. ;)

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J

Jonathan Kirwan 18 years ago

It runs under DOS, for now. Written in C. I'll fire up a VB for Windows version, if you prefer that. Shouldn't take too long to do that. Current link is at:

formatting link

Jon

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R

Rich Grise 18 years ago

Thanks! Do a VB version if you want to, but C is fine for here. :-)

Thanks! Rich

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Re: Simple inverter switch transistor circuit help needed

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