Simple ad hoc design continues to be useful

[Pimpom]

Have you ever designed and built something ad hoc (usually a
simple one) but later found it useful for other applications? I
have a few of those. For example, I made an adjustable constant
current source in the late '80s, specifically for sorting out my
old collection of zener diodes. It supplies a regulated current
that can be adjusted from 0.5 to 15mA at up to 50V.

I fully expected to discard it once the sorting was finished. 30+
years later, I'm still using it for a variety of jobs I never
envisioned when I first made it.

 

I have two large Rubbermaid tubs under my bench containing various testers, filters, RF gizmos, laser pulsers, and stuff like that.

The oldest is a six-pole 88-108 MHz bandpass filter for a quartz-synthesized FM receiver that I built as a new grad in 1981. It had a key pad, multiplexed 7-segment LED display, fuzzy dice, and everything--all done in 74F and LS TTL, with a dual-modulus ECL prescaler. (just kidding about the fuzzy dice.) I chucked the rest of it out when I went to grad school in 1983.

Another early one is an 80-MHz VCXO PLL multiplier that was part of my prototype atomic force microscope in 1987-88.

The one that gets used the most is the beam alignment gizmo I talked about the other day, built in 1990. It's very simple--a germanium quadrant photodiode running open-circuit, an LT1012 dual low-bias op amp, and two edge-reading, zero-centre galvanometers arranged perpendicularly to read X and Y.

The sensitivity goes like 1/beam diameter but is independent of laser power on accoun to the logarithmic characteristic of the diodes.

Cheers

Phil Hobbs

 

On Fri, 24 Apr 2020 14:03:21 +0530, Pimpom <nobody@nowhere.com> wrote:

Have you ever designed and built something ad hoc (usually a
simple one) but later found it useful for other applications? I
have a few of those. For example, I made an adjustable constant
current source in the late '80s, specifically for sorting out my
old collection of zener diodes. It supplies a regulated current
that can be adjusted from 0.5 to 15mA at up to 50V.

I fully expected to discard it once the sorting was finished. 30+
years later, I'm still using it for a variety of jobs I never
envisioned when I first made it.

Absolutely. And we document experiments and breadboards, whether they
seem to be useful or not. Sometimes they turn out to be useful years
later. We have 303 folders now in our PROTOS collection.

But my ancient flea-market HP6212 power supply is a fabulous
instrument. It goes to 120 volts and both the voltage and current
settings have coarse and fine knobs. That's great for testing LEDs and
zeners and, yesterday, VCOs.

https://www.dropbox.com/s/arbdkg6gocbpd66/HP6212A.JPG?dl=0




--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Winfield Hill]

jlarkin@highlandsniptechnology.com wrote...

But my ancient flea-market HP6212 power supply is a fabulous
instrument. It goes to 120 volts and both the voltage and
current settings have coarse and fine knobs. That's great
for testing LEDs and zeners and, yesterday, VCOs.

https://www.dropbox.com/s/arbdkg6gocbpd66/HP6212A.JPG?dl=0

Oops, the meter is offscale!


--
Thanks,
- Win

 

[Pimpom]

On 4/24/2020 8:55 PM, jlarkin@highlandsniptechnology.com wrote:

On Fri, 24 Apr 2020 14:03:21 +0530, Pimpom <nobody@nowhere.com> wrote:

Have you ever designed and built something ad hoc (usually a
simple one) but later found it useful for other applications? I
have a few of those. For example, I made an adjustable constant
current source in the late '80s, specifically for sorting out my
old collection of zener diodes. It supplies a regulated current
that can be adjusted from 0.5 to 15mA at up to 50V.

I fully expected to discard it once the sorting was finished. 30+
years later, I'm still using it for a variety of jobs I never
envisioned when I first made it.

Absolutely. And we document experiments and breadboards, whether they
seem to be useful or not. Sometimes they turn out to be useful years
later. We have 303 folders now in our PROTOS collection.

But my ancient flea-market HP6212 power supply is a fabulous
instrument. It goes to 120 volts and both the voltage and current
settings have coarse and fine knobs. That's great for testing LEDs and
zeners and, yesterday, VCOs.

https://www.dropbox.com/s/arbdkg6gocbpd66/HP6212A.JPG?dl=0

Yes, that looks positively ancient and the lighting enhances the
vintage look.

One early unforeseen application of my current supply was in
reviving old rechargeable batteries. NiCd batteries were still
widely used then, particularly 3.6V packs in toys, cordless
phones and the like. But where I live, getting replacements was
always a big problem and gadgets that were otherwise OK were
often discarded due to lack of a battery.

One day I decided to try charging a discarded battery with the
current source. At first, the voltage went up to the full 50V and
the current was just a tiny trickle, indicating a very high
internal resistance. But then the voltage started falling -
slowly, taking hours to drop to normal. With more charging, many
batteries became quite usable again.

I haven't tried to investigate the electrochemical action that
went on in the process of rejuvenation. Perhaps someone here
could enlighten us.

 

On 24 Apr 2020 08:52:30 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

jlarkin@highlandsniptechnology.com wrote...

But my ancient flea-market HP6212 power supply is a fabulous
instrument. It goes to 120 volts and both the voltage and
current settings have coarse and fine knobs. That's great
for testing LEDs and zeners and, yesterday, VCOs.

https://www.dropbox.com/s/arbdkg6gocbpd66/HP6212A.JPG?dl=0

Oops, the meter is offscale!

Current limit at max. Output shorted. Meter switch set to read
current.

Nothing really wrong about that. Of course I use a DVM when accuracy
matters.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[John Larkin]

On Fri, 24 Apr 2020 21:38:43 +0530, Pimpom <nobody@nowhere.com> wrote:

On 4/24/2020 8:55 PM, jlarkin@highlandsniptechnology.com wrote:
On Fri, 24 Apr 2020 14:03:21 +0530, Pimpom <nobody@nowhere.com> wrote:

Have you ever designed and built something ad hoc (usually a
simple one) but later found it useful for other applications? I
have a few of those. For example, I made an adjustable constant
current source in the late '80s, specifically for sorting out my
old collection of zener diodes. It supplies a regulated current
that can be adjusted from 0.5 to 15mA at up to 50V.

I fully expected to discard it once the sorting was finished. 30+
years later, I'm still using it for a variety of jobs I never
envisioned when I first made it.

Absolutely. And we document experiments and breadboards, whether they
seem to be useful or not. Sometimes they turn out to be useful years
later. We have 303 folders now in our PROTOS collection.

But my ancient flea-market HP6212 power supply is a fabulous
instrument. It goes to 120 volts and both the voltage and current
settings have coarse and fine knobs. That's great for testing LEDs and
zeners and, yesterday, VCOs.

https://www.dropbox.com/s/arbdkg6gocbpd66/HP6212A.JPG?dl=0


Yes, that looks positively ancient and the lighting enhances the
vintage look.

One early unforeseen application of my current supply was in
reviving old rechargeable batteries. NiCd batteries were still
widely used then, particularly 3.6V packs in toys, cordless
phones and the like. But where I live, getting replacements was
always a big problem and gadgets that were otherwise OK were
often discarded due to lack of a battery.

One day I decided to try charging a discarded battery with the
current source. At first, the voltage went up to the full 50V and
the current was just a tiny trickle, indicating a very high
internal resistance. But then the voltage started falling -
slowly, taking hours to drop to normal. With more charging, many
batteries became quite usable again.

I haven't tried to investigate the electrochemical action that
went on in the process of rejuvenation. Perhaps someone here
could enlighten us.

I used to recharge zinc-carbon batteries for my transistor radio when
I was a kid. It sort of worked.

(The original Regency 5-germanium-transisor AM thing. It cost $39, a
common weeks' pay in those days.)

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Fri, 24 Apr 2020 09:19:13 -0700, jlarkin@highlandsniptechnology.com
wrote:

On 24 Apr 2020 08:52:30 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:

jlarkin@highlandsniptechnology.com wrote...

But my ancient flea-market HP6212 power supply is a fabulous
instrument. It goes to 120 volts and both the voltage and
current settings have coarse and fine knobs. That's great
for testing LEDs and zeners and, yesterday, VCOs.

https://www.dropbox.com/s/arbdkg6gocbpd66/HP6212A.JPG?dl=0

Oops, the meter is offscale!

Current limit at max. Output shorted. Meter switch set to read
current.

Max current is 132 mA. The meter is very accurate.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[bitrex]

On 4/24/2020 1:42 PM, John Larkin wrote:

On Fri, 24 Apr 2020 21:38:43 +0530, Pimpom <nobody@nowhere.com> wrote:

On 4/24/2020 8:55 PM, jlarkin@highlandsniptechnology.com wrote:
On Fri, 24 Apr 2020 14:03:21 +0530, Pimpom <nobody@nowhere.com> wrote:

Have you ever designed and built something ad hoc (usually a
simple one) but later found it useful for other applications? I
have a few of those. For example, I made an adjustable constant
current source in the late '80s, specifically for sorting out my
old collection of zener diodes. It supplies a regulated current
that can be adjusted from 0.5 to 15mA at up to 50V.

I fully expected to discard it once the sorting was finished. 30+
years later, I'm still using it for a variety of jobs I never
envisioned when I first made it.

Absolutely. And we document experiments and breadboards, whether they
seem to be useful or not. Sometimes they turn out to be useful years
later. We have 303 folders now in our PROTOS collection.

But my ancient flea-market HP6212 power supply is a fabulous
instrument. It goes to 120 volts and both the voltage and current
settings have coarse and fine knobs. That's great for testing LEDs and
zeners and, yesterday, VCOs.

https://www.dropbox.com/s/arbdkg6gocbpd66/HP6212A.JPG?dl=0


Yes, that looks positively ancient and the lighting enhances the
vintage look.

One early unforeseen application of my current supply was in
reviving old rechargeable batteries. NiCd batteries were still
widely used then, particularly 3.6V packs in toys, cordless
phones and the like. But where I live, getting replacements was
always a big problem and gadgets that were otherwise OK were
often discarded due to lack of a battery.

One day I decided to try charging a discarded battery with the
current source. At first, the voltage went up to the full 50V and
the current was just a tiny trickle, indicating a very high
internal resistance. But then the voltage started falling -
slowly, taking hours to drop to normal. With more charging, many
batteries became quite usable again.

I haven't tried to investigate the electrochemical action that
went on in the process of rejuvenation. Perhaps someone here
could enlighten us.

I used to recharge zinc-carbon batteries for my transistor radio when
I was a kid. It sort of worked.

(The original Regency 5-germanium-transisor AM thing. It cost $39, a
common weeks' pay in those days.)

The early cable TV "encryption" system wasn't too sophisticated so if
you flipped down from channel 43 to the soft-core porn channel on 42 it
would show up for about a half-second before the scrambler kicked in. so
we devised a timer + relay circuit that would rapidly flip the channel
back and forth from the remote control PCB.

And that's how I got where I am today

 

[John Larkin]

On Fri, 24 Apr 2020 15:42:10 -0400, bitrex <user@example.net> wrote:

On 4/24/2020 1:42 PM, John Larkin wrote:
On Fri, 24 Apr 2020 21:38:43 +0530, Pimpom <nobody@nowhere.com> wrote:

On 4/24/2020 8:55 PM, jlarkin@highlandsniptechnology.com wrote:
On Fri, 24 Apr 2020 14:03:21 +0530, Pimpom <nobody@nowhere.com> wrote:

Have you ever designed and built something ad hoc (usually a
simple one) but later found it useful for other applications? I
have a few of those. For example, I made an adjustable constant
current source in the late '80s, specifically for sorting out my
old collection of zener diodes. It supplies a regulated current
that can be adjusted from 0.5 to 15mA at up to 50V.

I fully expected to discard it once the sorting was finished. 30+
years later, I'm still using it for a variety of jobs I never
envisioned when I first made it.

Absolutely. And we document experiments and breadboards, whether they
seem to be useful or not. Sometimes they turn out to be useful years
later. We have 303 folders now in our PROTOS collection.

But my ancient flea-market HP6212 power supply is a fabulous
instrument. It goes to 120 volts and both the voltage and current
settings have coarse and fine knobs. That's great for testing LEDs and
zeners and, yesterday, VCOs.

https://www.dropbox.com/s/arbdkg6gocbpd66/HP6212A.JPG?dl=0


Yes, that looks positively ancient and the lighting enhances the
vintage look.

One early unforeseen application of my current supply was in
reviving old rechargeable batteries. NiCd batteries were still
widely used then, particularly 3.6V packs in toys, cordless
phones and the like. But where I live, getting replacements was
always a big problem and gadgets that were otherwise OK were
often discarded due to lack of a battery.

One day I decided to try charging a discarded battery with the
current source. At first, the voltage went up to the full 50V and
the current was just a tiny trickle, indicating a very high
internal resistance. But then the voltage started falling -
slowly, taking hours to drop to normal. With more charging, many
batteries became quite usable again.

I haven't tried to investigate the electrochemical action that
went on in the process of rejuvenation. Perhaps someone here
could enlighten us.

I used to recharge zinc-carbon batteries for my transistor radio when
I was a kid. It sort of worked.

(The original Regency 5-germanium-transisor AM thing. It cost $39, a
common weeks' pay in those days.)


The early cable TV "encryption" system wasn't too sophisticated so if
you flipped down from channel 43 to the soft-core porn channel on 42 it
would show up for about a half-second before the scrambler kicked in. so
we devised a timer + relay circuit that would rapidly flip the channel
back and forth from the remote control PCB.

And that's how I got where I am today

Thank you for sharing.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[bitrex]

On 4/24/2020 4:38 PM, John Larkin wrote:

On Fri, 24 Apr 2020 15:42:10 -0400, bitrex <user@example.net> wrote:

On 4/24/2020 1:42 PM, John Larkin wrote:
On Fri, 24 Apr 2020 21:38:43 +0530, Pimpom <nobody@nowhere.com> wrote:

On 4/24/2020 8:55 PM, jlarkin@highlandsniptechnology.com wrote:
On Fri, 24 Apr 2020 14:03:21 +0530, Pimpom <nobody@nowhere.com> wrote:

Have you ever designed and built something ad hoc (usually a
simple one) but later found it useful for other applications? I
have a few of those. For example, I made an adjustable constant
current source in the late '80s, specifically for sorting out my
old collection of zener diodes. It supplies a regulated current
that can be adjusted from 0.5 to 15mA at up to 50V.

I fully expected to discard it once the sorting was finished. 30+
years later, I'm still using it for a variety of jobs I never
envisioned when I first made it.

Absolutely. And we document experiments and breadboards, whether they
seem to be useful or not. Sometimes they turn out to be useful years
later. We have 303 folders now in our PROTOS collection.

But my ancient flea-market HP6212 power supply is a fabulous
instrument. It goes to 120 volts and both the voltage and current
settings have coarse and fine knobs. That's great for testing LEDs and
zeners and, yesterday, VCOs.

https://www.dropbox.com/s/arbdkg6gocbpd66/HP6212A.JPG?dl=0


Yes, that looks positively ancient and the lighting enhances the
vintage look.

One early unforeseen application of my current supply was in
reviving old rechargeable batteries. NiCd batteries were still
widely used then, particularly 3.6V packs in toys, cordless
phones and the like. But where I live, getting replacements was
always a big problem and gadgets that were otherwise OK were
often discarded due to lack of a battery.

One day I decided to try charging a discarded battery with the
current source. At first, the voltage went up to the full 50V and
the current was just a tiny trickle, indicating a very high
internal resistance. But then the voltage started falling -
slowly, taking hours to drop to normal. With more charging, many
batteries became quite usable again.

I haven't tried to investigate the electrochemical action that
went on in the process of rejuvenation. Perhaps someone here
could enlighten us.

I used to recharge zinc-carbon batteries for my transistor radio when
I was a kid. It sort of worked.

(The original Regency 5-germanium-transisor AM thing. It cost $39, a
common weeks' pay in those days.)


The early cable TV "encryption" system wasn't too sophisticated so if
you flipped down from channel 43 to the soft-core porn channel on 42 it
would show up for about a half-second before the scrambler kicked in. so
we devised a timer + relay circuit that would rapidly flip the channel
back and forth from the remote control PCB.

And that's how I got where I am today


Thank you for sharing.

Engineers solve practical problems, y'know

 

[whit3rd]

On Friday, April 24, 2020 at 1:33:34 AM UTC-7, Pimpom wrote:

Have you ever designed and built something ad hoc (usually a
simple one) but later found it useful for other applications?

Oh, yeah. For finding interference sources in a sensitive
motion-feedback gizmo, I wound a search coil and soldered
it to an oscilloscope-friendly connector. The first one vanished
right after I demo'ed it to the guy in the lab down the hall. I think
two or three others followed.

If there's not one in my junk drawer now, it's OK; all the parts of
one are definitely in my junk drawer. Yours, too, I guess.

 

On Sat, 25 Apr 2020 21:25:53 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

On Friday, April 24, 2020 at 1:33:34 AM UTC-7, Pimpom wrote:
Have you ever designed and built something ad hoc (usually a
simple one) but later found it useful for other applications?

Oh, yeah. For finding interference sources in a sensitive
motion-feedback gizmo, I wound a search coil and soldered
it to an oscilloscope-friendly connector. The first one vanished
right after I demo'ed it to the guy in the lab down the hall. I think
two or three others followed.

If there's not one in my junk drawer now, it's OK; all the parts of
one are definitely in my junk drawer. Yours, too, I guess.

An unshielded drum-core inductor is a great mag field pickup.

Radiator, too.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[whit3rd]

On Sunday, April 26, 2020 at 9:43:29 AM UTC-7, jla...@highlandsniptechnology.com wrote:

An unshielded drum-core inductor is a great mag field pickup.

Radiator, too.

Yes, and at a PPOE I wound another coil and packaged it so it could
be clamped to a multiple coax cable. It injected enough test signal
to do a bench-verification of an ultrasound head that had a few
hundred separate signal channels. Had to arrange a good mechanical
clamp for the tests to get consistent results, though.