Forums

Simple ad hoc design continues to be useful

Started by Pimpom April 24, 2020
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
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
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
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
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
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
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