Increment/Decrement Control Loops

[john jardine]

Anyone know the history of Increment/Decrement Control loops?

There's a paragraph on page 56 of the October "Microwaves and RF"
magazine about AGCing a VCO using an up/down counter and D-A in an
increment/decrement control... touting it as if it's the next best
thing to sliced bread.

But I hardly think it's novel... I was setting the timing of
automobile ignition systems in 1968, but used a squirt of charge
into/out-of a capacitor to increment/decrement.

The paragraph references an IEEE article in October's "IEEE
Transactions on Instrumentation and Measurement", which I can't access
since I object to $35/month for the privilege (as I noted today as I
renewed my memberships).

Maybe someone who subscribes to that service can look it up?

Thanks!

...Jim Thompson

Sounds pretty much like the old 'huff-and-puff' VFO stabiliser the radio
hams used.
regards
john

 

[Jim Thompson]

Anyone know the history of Increment/Decrement Control loops?

There's a paragraph on page 56 of the October "Microwaves and RF"
magazine about AGCing a VCO using an up/down counter and D-A in an
increment/decrement control... touting it as if it's the next best
thing to sliced bread.

But I hardly think it's novel... I was setting the timing of
automobile ignition systems in 1968, but used a squirt of charge
into/out-of a capacitor to increment/decrement.

The paragraph references an IEEE article in October's "IEEE
Transactions on Instrumentation and Measurement", which I can't access
since I object to $35/month for the privilege (as I noted today as I
renewed my memberships).

Maybe someone who subscribes to that service can look it up?

Thanks!

...Jim Thompson

 

[Jim Thompson]

Anyone know the history of Increment/Decrement Control loops?

There's a paragraph on page 56 of the October "Microwaves and RF"
magazine about AGCing a VCO using an up/down counter and D-A in an
increment/decrement control... touting it as if it's the next best
thing to sliced bread.

But I hardly think it's novel... I was setting the timing of
automobile ignition systems in 1968, but used a squirt of charge
into/out-of a capacitor to increment/decrement.

The paragraph references an IEEE article in October's "IEEE
Transactions on Instrumentation and Measurement", which I can't access
since I object to $35/month for the privilege (as I noted today as I
renewed my memberships).

Maybe someone who subscribes to that service can look it up?

Thanks!

...Jim Thompson

[snip]

Sounds pretty much like the old 'huff-and-puff' VFO stabiliser the radio
hams used.
regards
john

That's what I thought, too.

...Jim Thompson

 

[Spehro Pefhany]

Anyone know the history of Increment/Decrement Control loops?

There's a paragraph on page 56 of the October "Microwaves and RF"
magazine about AGCing a VCO using an up/down counter and D-A in an
increment/decrement control... touting it as if it's the next best
thing to sliced bread.

But I hardly think it's novel... I was setting the timing of
automobile ignition systems in 1968, but used a squirt of charge
into/out-of a capacitor to increment/decrement.

The paragraph references an IEEE article in October's "IEEE
Transactions on Instrumentation and Measurement", which I can't access
since I object to $35/month for the privilege (as I noted today as I
renewed my memberships).

Maybe someone who subscribes to that service can look it up?

Thanks!

...Jim Thompson

Try looking for "single-speed floating control". I think it's a really
old and not-so-great control strategy.


Best regards,
Spehro Pefhany

 

[Max Hauser]

"Jim Thompson" in news:[email protected]...

Anyone know the history of Increment/Decrement Control loops?

... AGCing a VCO using an up/down counter and D-A in an
increment/decrement control...

I haven't seen the original, but from the description here, it sounds like a
good old digital integrator. In case anyone who is reading this has not run
into or thought about it, a digital up-down counter is precisely a DSP
integrator for a one-bit input ("+- 1"). (At times in the past we made very
good use of that property, and other properties of one-bit arithmetic, in
digital filters for oversampling data converters.) And an integrator is the
heart of many control loops.

In the early days of digital forays into the system-simulation world
pioneered by analog computers (more on those in classic books by Jackson,
and by Korn and Korn), people built special-purpose digital integrators, and
then made loops out of them that would solve differential equations over
time, just like electronic analog computers did. They were called Digital
Differential Analyzers (DDAs). A single digital integrator in an AGC
control loop would be a grandchild of those.

-- Max

 

[Jim Thompson]

Try looking for "single-speed floating control". I think it's a really
old and not-so-great control strategy.


Best regards,
Spehro Pefhany

I thought it worked rather well. My scheme looked at dwell, decided
if it was early or late and moved a threshold accordingly... this
happened _after_ firing so was not subject to noise from the spark.

Just like having an elf sitting there turning a knob just a small
amount after each firing ;-)

...Jim Thompson

 

[Spehro Pefhany]

I thought it worked rather well. My scheme looked at dwell, decided
if it was early or late and moved a threshold accordingly... this
happened _after_ firing so was not subject to noise from the spark.

Just like having an elf sitting there turning a knob just a small
amount after each firing ;-)

...Jim Thompson

I think it generally works better if the elf moves the knob more for
large differences and less for small differences.


Best regards,
Spehro Pefhany

 

[Jim Thompson]

I think it generally works better if the elf moves the knob more for
large differences and less for small differences.


Best regards,
Spehro Pefhany

If you choose a fixed increment that is small enough it closes at
"left-right-left-right-left......" ;-)

Driving a big-assed T-bird (400+CID) in 1968, up and down 101 (near
Sunnyvale) at over 100MPH, I was never able to cause the ignition to
stumble... scared the hell out of my boss, though ;-)

...Jim Thompson

 

[Jim Thompson]

I think it generally works better if the elf moves the knob more for
large differences and less for small differences.


Best regards,
Spehro Pefhany

Perhaps I should elaborate. Waveform form (simplified, it's more
rounded) from magnetic pickup in distributor:

_ _ _
/ | / | / |
| / | /
| / | /
----------------------- THRESHOLD
| / | /
|_/ |_/

Downstroke is firing. When ramp crosses threshold power device
(driving coil) turns on. So this crossing determines "dwell".

Device control is simple-minded (my preference ...

Device has three states:

Off... Fired
Saturated, coil charging
Current mode, regulated at 5.5Amp

So I only look at two conditions... when firing occurred was I in
saturation or in current regulation.

If device was in saturation, dwell didn't start soon enough so I
decrement the threshold. If device was in current regulation dwell
started too soon so I increment the threshold.

Worked like a champ.

...Jim Thompson

 

[Tom Seim]

Anyone know the history of Increment/Decrement Control loops?

There's a paragraph on page 56 of the October "Microwaves and RF"
magazine about AGCing a VCO using an up/down counter and D-A in an
increment/decrement control... touting it as if it's the next best
thing to sliced bread.

But I hardly think it's novel... I was setting the timing of
automobile ignition systems in 1968, but used a squirt of charge
into/out-of a capacitor to increment/decrement.

The paragraph references an IEEE article in October's "IEEE
Transactions on Instrumentation and Measurement", which I can't access
since I object to $35/month for the privilege (as I noted today as I
renewed my memberships).

Maybe someone who subscribes to that service can look it up?

Thanks!

...Jim Thompson

I will send you a copy if that is your real email address.

 

[Jim Thompson]

I will send you a copy if that is your real email address.

I have already been sent a copy, Thanks! (The header E-mail address
is false... read the SIG to obtain a valid E-mail address.)

...Jim Thompson