Looking for the best of critique, not the musings of students

[OlPhart]

Howdy, Been in this gig 30+ years, my best colleague passed away 2 yrs ago.
I'm looking for the occasional "soundingboard" to keep me from barking up too many "stop signs".
I'll Certainly do the same in return. I suck at analog, if only because I don't do enough of it.
Digital hardware & software are my domain.

Been doing assembler level controllers since 1978 (no kidding, Cromemco S100 bus Z80 era).
Building combinatorial hardware since 1978 (what is now integrated as a controller).
Wrote/built Zilog from 1978 t0 1998, went Freescale (Motorola) since (colleague's adamant preference).

I'll sign in every day or so, looking for a new colleague...
OR kick my email, I'm not in a rush, but hate running down "blind alleys" (ergo "stop signs").
Got a Wheatstone bridge conversion I'm on the 8th (!!) analog version of.... TNX in advance... <<<)))

 

[ronsimpson]

S100 bus! I had the first "personal computer" in the dorm. S100 (2.5mhz Z80) Wire-wrapped some of the boards.
Retired and dead colleagues..........I miss them!
I do mostly analog and power supplies.
I like FPGAs but not good at it.

Every time I see a stop sign I raise one leg. lol

What problem are you having with your Wheatstone Bridge?

 

[4pyros]

I feel for you guys and I would lift a leg too but can't.
In and out of just about every aspect of electronics for the better part of 40 years.
Saw the magic smoke at nine years of age, been hooked ever since.

 

[JimB]

I think of myself as a bit of a generalist when it comes to analogue/digital, my favourite thing is RF.

Lifting legs? Yes if I can do it at my own pace.
Everyday something different in my body aches.
As long as all the aches don't do their thing all at once it is a good day!

JimB

 

[MikeMl]

More than one Old Fart on here... Learned how to solder in 1958.

 

[4pyros]

Rebuilt a wave solder machine when I was 16.

 

[cowboybob]

Me too, Mike. Built my first Knight Kit (Span Master) in '58 (10 yo). Got my ham ticket in '59.

Been at it (analog, digital around '82 - Apple II+s with Toshiba PLCs) ever since... Currently enjoying playing with Arduino(AtMega32).

 

[4pyros]

I just picked up an Arduino U3, I hope I have time to play with it.

 

[OlPhart]

Well, it's gratifying & heartening to enjoin such company.
The situation I've been battling for 3 years (!!) is an instrument that measures absorption in media.
The original object was designed in the late 1950s. It uses a Wheatstone bridge with 2 photovoltaic cells as sensors.
The cells/sensors are connected head to tail with a potentiometer to balance them as Reference & Sample sensed values.
Operator then offsets/reduces the Reference value with a specified value, and gives the Sample its' contamination,
the results' end point is the time it takes for the contamination to cause the Sample
to absorb enough to match the Referenced specified offset value.
(sorry to be vague on operation, customer is kind of touchy on that)
The 1950s designs' components are either not available and/or silly expensive.
Ergo, I was commissioned to design a modern equivalent.

What's been mentally blocking me was the thinking that the bridge actually needed to behave with + & - voltages.
While true, but if only that the common point (head<->tail opposite end of balancing pot) is locked to 0.00VDC.
The popping sound you (may) hear is the cranial-sphincterectomys' result of just pushing that common point
enough above 0.00VDC such that the reference sensor is >0.00VDC as well (DUH).
Now I can use all conventional amps, don't need protection limiters on uC ADC inputs.... Massive DUH.

I'm not looking for design critique on this project (unless this recent approach is faulty [again]).
What I'm going after with (collectively) you, is to not need the "popping" sound... I bounce a concept off "you" and you critique it.
I'll be More than willing to do the same (you may have observed my missives.. while not kind, I think fair).
That this is 3 years/8 analog designs proves I'm not worth a stink at analog.
I'll counter that in digital hdwe & assembler level swre, I make up for this... (but that's My story..)
Thanks for "listening", tip your waitress (to the left), I'll be here all week....... G.H. <<<)))

 

[4pyros]

Has this machen not been updated or outdated over the last fifty years?

 

[dougy83]

Is this basically the circuit you're working on? You don't need a dual-rail excitation voltage for the bridge; you just use a differential amplifier on the bridge outputs.

P.S. You have managed to incorrectly place every single possessive apostrophe in your post.