Unusual Bias Method

Hell, you can't do it either.

If you like no capacitance in your wiring, you live in a different universe from the rest of us.

In a later life I might have used a diode. We improve our skill-set over the years... at least some of us do... some just bloviate >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

On a sunny day (Wed, 27 Nov 2013 16:05:51 -0600) it happened John Fields wrote in :

Well, you _advised_ the OP, seen here by anyone.

Customers do not like that attitude.

Its a special sub-case, and the rest is missing too: decode to RS232, detect changing digits, prevent changing digits (false positives), and BUILD a total working example. You got work to do ;-)

And in _infinity_ as other have mentioned, there are many kinds of infinity, J.L.'s use of it was totally acceptable.

On a sunny day (Wed, 27 Nov 2013 17:25:49 -0700) it happened Jim Thompson wrote in :

There is, at least on earth, always some capacitance to ground.

I once got comment after designing a big rack full of PCBs why ony support at bottom side. I asked if he expected gravity to fail shortly?

You just watch too many space operas.

On a sunny day (Wed, 27 Nov 2013 17:43:06 -0800) it happened John Larkin wrote in :

The normal RC to ground at the output is missing, sometimes called 'Boucherot cell' or 'Zobel network', this amp is unstable by default and WILL oscillate somewhere on the sine peaks at some loads. He must have seen that in his real simulation and now does not want to post that. Darlingtons in an output stage are not so easy to stabilize, may even be different or unstable with transistors from a different batch or manufacturer. My experience.

Oscillation then typically happens at a much higher frequency than audible, and can blow up tweeters.

I already pointed that out earlier.

It is an amateur design.

On a sunny day (Wed, 27 Nov 2013 19:05:21 -0700) it happened Jim Thompson wrote in :

Speakers are not resistive only.

Do you guys really have to quote 200000 header lines?

--- I provided the OP with a schematic and a sim of a seven-segment to BCD encoder, which is what he asked for, and later on - as an aside

- a viable way to get signal from the segments.

We both know that it's possible to detect the on-ness and of-ness of an LED using a photocell, but since doing it that way is hardware based and you're a code monkey at heart, admitting to it gets your knickers in a bunch and is contributing to the [unnecessary] growing length of this thread.

---

--- Kissing customer ass is more likely to get you in trouble, upstream, than standing your ground when you know you're right, and "NO BID" is always an option.

YMMV.

---

--- Having 12 spare IOs available from his PLC, the OP specifically asked for 3 parallel BCD digits as inputs to the PLC, which 3 of my encoders will give him, inherently, negating the need for RS-232.

My circuit can't _prevent_ changing digits, since that's what the PLC is doing, but it _can_ encode them into parallel BCD, which is what the OP asked for.

As for false positives, the long-term latency of the digits between changes should take care of that.

Build???

When one can simulate at this stage, why waste resources?

---

--- With a mind-set like yours, that goose-stepping march in lockstep is totally understandable.

Did you also have cootie vaccinations? There was a girl named Sylvia who claimed to have "lifetime cootie shots."

--

Reply in group, but if emailing remove the last word.

Didn't come up. I never went to a co-ed school, except kindergarten.

Cheers

Phil Hobbs

Ok Obama!

Jamie

I've never seen it work. You posted a PDF that sort of looks like it works, but you never posted an LT Spice netlist that could be tested by everyone else. Actually, the comparator duty cycle is plainly visible in the PDF, and that shows that it's not working. 70 uA * 0.02 = 1.4 uA, not enough.

In real life, I suspect it won't. But that doesn't matter: I've demonstrated that, in your 1 KHz case, the duty cycle is low and the resulting averaged Q3 current is too low to bias up the darlingtons. And tolerances and Q2 self-heating will kill the Q3 current entirely.

Say something concrete and quantitative about those facts.

(Is there a way in LT Spice to change the temperature of a single transistor? Raising Q2 by 40C would be interesting.)

Of course.

No.

I've posted numbers, not sand. Explain the 1 KHz duty cycle/current problem. Explain away the DC problems.

Gonna make them sign an NDA? You now refuse to post it here, after saying that you would, because you KNOW now that it doesn't work.

You didn't post numbers, you posted platitudes. What DC problems? Just more sand in the air.

I never said I'd post a spice model, I said I'd simulate it. You made up that "model" nonsense yourself.

Model freely to anyone BUT Larkin ;-)

I _did_show_that_it_works! You're like Obama... lie often enough and big enough and you think the world believes you. Only your sickophants do >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

70 uA * 0.02 sure sounds like numbers to me. But you and JF use nonstandard mathematical concepts.

you posted platitudes. What DC problems?

You know what will happen if you post an LT Spice sim file. So you don't dare.

Quit weaseling and show us some numbers. What is the average current in R7 in your 1 KHz PDF example? I originally estimated 1.2 uA. Not enough.

JL >(Is there a way in LT Spice to change the temperature of a single JL >transistor? Raising Q2 by 40C would be interesting.)

Yes, Some one here showed me how to do it, I'll pass it one :)

control+right click on the subjects name (component), gets you the dialog for the spice options. Enter a "spiceline" = temp 10 for example. etc.. Jamie

Cool. Q2 will self-heat by 40C or so. If I set its temp to 60C, the "on" current in Q3 drops from 60 uA to 14 uA, which breaks the circuit even more than it was broken already. The servo action at 1 KHz is essentially zero.

14 uA * 0.02 = 280 nA

280 nA * 100K = 28 millivolts.

Numbers!

Gotta go string Christmas lights on the cabin. TidPid, the local utility, gives us free LED strings if we bring in old, dead incendescents. They also give away shower heads, CF lamps, stuff like that.

Larkin's phenomenal ignorance on display, thetaJA of 2N3904 is 200°C/W

Dissipation is 100mW, like who cares... Larkin is totally clueless about bipolar bias techniques.

You ought to be careful with statements like that, you're so ignorant of bipolar behavior you have even the bias currents all wrong, Ic(Q3) is a pulse to 70uA at each zero crossing.

Likewise you can't cope with anything more than one transistor at a time, so your bias estimates are just SWAG's.

Indeed! You're wrong again... and you have no clue.

But I'm calling your bluff. Subcircuit will be posted shortly, including all needed models. Thus the troops can check out each of your claims and see for themselves what a village idiot you are >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

To go along with that schematic, here is the subcircuit that should work in all modern flavors of Spice...

...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

And now the subcircuit...

From: Jim Thompson Newsgroups: sci.electronics.design Subject: Re: Unusual Bias Method - Simulation Date: Thu, 28 Nov 2013 13:36:42 -0700 Message-ID:

...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

| 1962 | I love to cook with wine. Sometimes I even put it in the food.