Re: Circuit Analysis with LTSpice: 12-V Lamp Flasher

Almost all our products were simulated in LT Spice, and that steered or verified the designs.

We don't prototype many products; they are too complex. It's more efficient to design, simulate, review, and manufacture. If the engineering is done right, you can sell rev A. I nkow of one giant organization that formally plans for six PCB spins before production. Why bother to be careful on the first few?

We do breadboard little subcircuits if we're not sure how they will behave. Data sheets can be vague. Dremeling is fun.

Hers's a product sim.

I did this all analog, in LT Spice, to get the dynamics right. Most of this will actually be done in an FPGA.

Tis true the Spice won't help you With a simple radio set:

No worries all's not nyet Spice fiddling's a safe bet...

Danke,

Why not?

Jeroen Belleman

It wouldn't work without one. Xtal sets need hi-z earphones for obvious reasons and crystal earpieces are ideal.

Yes, but they need a leakage resistor over the earpiece so the diode kan stay doing its work. A pencil stripe will do. Just as the inductive earpiece needs a parallel capacitor for optimal work (often the wiring functions as such).

Arie

Good question. And, with all due respect, you ought to post some Spice to show me how you do it.

Danke,

Good question. Although it primary provides power for future, yet-to-be developed protos, it also fulfills a fundamental function for a crystal radio set.

Think about it.

Hint: the power cord conveniently connects three cables to the case, but not all are used by this crystal circuit.

# # #

My simplest schematic shown uses a hi-Z earphone (although its schematic symbol sucks IMHO). The demodulating diode depicted works without a parallel capacitor.

Danke,

Along with assorted audio convertors, there's at least one old Soviet military headset here:

(A pariah perhaps to patriots stirred by sanction spirit.)

Danke,

...

...

I used to be a developer at such a giant organization and we did usually have many spins of the PCB.

However it was rarely because there were any faults with the designs, each revision usually worked as intended, designers were very careful with each revision with a full suite of simulations of the design including AC and DC validation of the PCB layout automatically ran at each stage.

The various revisions were planned so that the other parts of the organization would have hardware to use for development. It was not unusual for 5,000 prototype units to be manufactured for such work.

For example the final form factor was not known until the external product design was completed which usually didn't happen until fairly late in development.

ASIC design, human factors engineering, software development, manufacturing, quality assurance, regulatory and other groups all had their needs and input into the final design but they needed something to work with in the meanwhile.

The first revisions would be in a development form factor where each major function had its own PCB that mounted on a large mother board.

Occasionally unusual interactions would occur when the final form factor designs were created. I was involved in one critical aspect where acoustic noise from a ceramic capacitor was getting into a microphone as they ended up only being about 3mm apart; this was not an issue on the development board where there were many centimeters between them. I solved it by using a combination of tantalum and COG ceramic capacitors; Tantalum capacitors in 0402 form factor were becoming available just in time for production.

kw

Something akin to this.

Jeroen Belleman

================================================ Version 4 SHEET 1 880 680 WIRE -144 96 -176 96 WIRE -32 96 -64 96 WIRE 272 96 176 96 WIRE 352 96 272 96 WIRE 464 96 416 96 WIRE 512 96 464 96 WIRE 544 96 512 96 WIRE -176 128 -176 96 WIRE -32 128 -32 96 WIRE 176 128 176 96 WIRE 272 128 272 96 WIRE 464 128 464 96 WIRE 544 144 544 96 WIRE -176 240 -176 208 WIRE -32 240 -32 208 WIRE 176 240 176 208 WIRE 272 240 272 192 WIRE 464 240 464 208 WIRE 544 240 544 208 FLAG 176 240 0 FLAG 272 240 0 FLAG 464 240 0 FLAG 544 240 0 FLAG -32 240 0 FLAG -176 240 0 FLAG 512 96 out SYMBOL ind2 160 112 R0 SYMATTR InstName L1 SYMATTR Value 16µ SYMATTR Type ind SYMBOL cap 256 128 R0 SYMATTR InstName C1 SYMATTR Value 6.28n SYMBOL diode 352 112 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D1 SYMATTR Value AA112 SYMBOL res 448 112 R0 SYMATTR InstName R1 SYMATTR Value 1meg SYMBOL cap 528 144 R0 SYMATTR InstName C2 SYMATTR Value 10n SYMBOL ind2 -48 112 R0 SYMATTR InstName L2 SYMATTR Value 16µ SYMATTR Type ind SYMBOL bv -176 112 R0 WINDOW 3 -186 181 Left 2 SYMATTR InstName B1 SYMATTR Value V=10k*(1+sin(time*1k*2*pi))*sin(time*1meg*2*pi) SYMBOL res -48 80 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R2 SYMATTR Value 1 TEXT 72 0 Left 2 !.tran 5m TEXT 0 112 Left 2 !K12 L1 L2 1u TEXT -152 0 Left 2 ;Transmitter TEXT 264 0 Left 2 ;Crystal set receiver

<snip>

Brilliant - you're a gentleman, a scholar, and a genius!

While my mind mulled how to capture the crystal circuit in Spice, it never occurred to me inject its input with a transformer.

Your sim will be put to good use. Thank you.

# # #

Readers who overlooked the final two lines of my poem (the stanzas someone snipped along the way) will note how they say something similar to "let he who doesn't Spice fiddle cast the first stone."

ROTFLMAO.

Danke,

You don't expect high fidelity from a crystal set, but OK, fair enough. C2 was meant to model a piezo earbud. I should actually measure one...

I got the values of C! and L1 wrong. C1=300pF is more reasonable, and then L1=84.43uH. In practice, of course, C1 would be tuned and L1 would be fixed at 80uH or so, but either way works.

The voltage of B1 and the tranformer coupling factor are just guesses, based on the knwoledge that crystal sets actually do work.

Jeroen Belleman

LEDs require relatively large amounts of current, so I don't see how that would be possible, John. There's only *one* bloke I can think of who could conceivably pull that off and he's long dead, sadly. Edison's nemesis:

Neon or similar would be far more easily achievable I reckon.

Somewhere I still have an old timey wavemeter that works off this principle. When tuned to the same frequency as a nearby transmitter, the bulb lights. Amazing how far we've come in 100 years.

The crystal cult concurs with your circumspect constructive criticism:

It turns out a 0.001 uF cap and an 82 k resistor in parallel with the earphone increases amplitude perceptibly. Thank you for sharing.

Danke,

A good crystal set needs to squeeze as much precious power as possible out of a radio wave. A solid connection to ground fulfills a fundamental function - it firmly anchors the signal. The NEMA ground cable provides a handy ground connection, even though the power supply remains unused.

Anyhow, now's the time to put the previously passive power supply to good use. It's possible to eliminate the earphone with an electronic precision voltage reference:

# # #

World Radio Day – February 13, 2024

Radio: A century informing, entertaining and educating

World Radio Day 2024: How Kenya’s Community Radios are Strengthening Democracy

World Radio Day 2024: Theme, History, Significance & Everything Else You Must Know

Danke,

Potato guns aside, the last rocket launched by me happened a long time ago. If another small rocket is ever again launched by me it may carry a crystal radio:

Danke,

Government inflation drove up a rocket radio's price 7,200% since the 1950s:

Danke,