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Re: What is sidereal time? Why is it used? And How to make it?

 

On Friday 24 January 2025 06:38:45 pm wn4isx via groups.io wrote:
Note 2: The CMOS 7555 are a Xitch to get working properly!
How so?

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Re: ?My Temperature Probe melted

wn4isx
 

Try a 15k or 20k pot....turn the knob and the display should change.
?
What is sidereal time? Why is it used? And How to make it?

wn4isx
 

86164.0905??(23 h 56 min 4.0905?s or 23.9344696 h).?

Another way to understand this difference is to notice that, relative to the stars, as viewed from Earth, the position of the Sun at the same time each day appears to move around Earth once per year. A year has about 365.24 solar days but 366.24 sidereal days. Therefore, there is one fewer??per year than there are sidereal days, similar to an observation of the?.?This makes a sidereal day approximately?365.24/366.24??times the length of the 24-hour solar day.

?

?

https://adsabs.harvard.edu/full/1984IAPPP..17...55D

Pages 55 ~ 61

?

I received an email asking "What is sidereal time and where is it used?"

And

"How do you derive it from 60Hz?"

?

Wiki has a fairly good article on sidereal time.

Sidereal time is used by astronomers. There are special motorized drives that change the azimuth (degrees north-south) and elevation (height) to keep a star centered in a telescope

?

Any sane person uses a app for their Android or iPhone. But there are special people like My Crazy Cousin who lives north of Santa Fe who is an advanced amateur astronomer.

?

Anyway My Crazy Cousin wanted a dual display clock, one display would show Mountain Standard Time, the other Sidereal time, both synched to WWV.

?

I happen to have some unused National Semiconductor LSI MM5314 single IC clock chips.

I used green 7 segment LEDs for the MST and red 7 segment LEDs for the Sidereal.

?

I used an inexpensive precision 10MHz canned TTL oscillator with internal heater. She upgraded to a ~$150 GPS disciplined oscillator with a 10MHz output.

?

I used a PIC programmed with magic code to convert 10MHz to 60MHz.

http://leapsecond.com/pic/

http://leapsecond.com/pic/picdiv-list.htm

?

scroll down to

pd60.asm:;?? PD60 -- PIC "4-pin" frequency divider (10 MHz to 60 Hz)

?

You feed 10MHz into the PIC and get 60Hz out, the accuracy of the 60Hz depends on the accuracy of the input 10MHz.

?

Then open

?

https://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1984IAPPP..17...55D&defaultprint=YES&filetype=.pdf

?

And you see one way way to modify 60Hz to feed "sidereal 60Hz" to a LSI clock chip to display sidereal time.

?

I used the same logic but with CMOS chips.

?

Now if the Leapsecond.com only had a 10MHz to "60Hz Sidereal".....

?

Now as I said at the beginning, any sane person would use an android device, perhaps an older tablet for a nice large display....but My Crazy Cousins "observatory" is in a marginal cellphone coverage so she maybe she isn't so crazy.

?

[She also happens to be my favorite cousin. A really nice if somewhat dingbatty person.]

?

My personal GTM/EST/Sidereal clock uses 3 MN5314, on for each time zone and uses the chip enable pin to turn on the desired time zone. Of course mine was built from 1976 through 1980 in stages.

?

I came up with a logic circuit using 74LS chips that achieved the same function. I replaced my 74LS design with the new CMOS.

?

Unless you are an astronomer, or total geek, you will never need sidereal time, but this is one 'easy' way to obtain it.

?

Of course she could simply have spent ~$200 at

https://brgprecision.com/products/stand_alone_clocks/sidereal.php

?

?

Note 1: I've never actually used the Sidereal function, the only really clear nights in Kentucky suitable for astronomy are when there are no clouds and it's -10...and I'll be inside where it is warm and either asleep in our bed or listening to shortwave.

?

Note 2: The CMOS 7555 are a Xitch to get working properly!

?

Note 3: I saw a scheme in a British or German electronic hobbyist magazine that used logic to switch the 50/60Hz input from 60 to 50 every so many cycles to obtain sidereal time. It's been over 50 years I don't recall the circuit.

?

Note 4: For a really hard way to get regular and sidereal time

https://www.worldradiohistory.com/UK/Practical-Electronics/80s/Practical-Electronics-1981-10.pdf

?

Note: 5: It should be possible to use the leapsecond.com 10MHz to sidereal 1 pps to drive one of those cheap analog clocks.

?

They have a 32?kHz crystal, "IC" to produce 1 PPS, it'd require some experimentation but it should work.

Since My Crazy Cousin is dyslexic, like me, analog clocks are viewed as the work of the devil and you are on your own here.

This might help

https://sound-au.com/clocks/timebase.html

and

http://leapsecond.com/pic/picdiv-list.htm

scroll down to 

pd29.asm:;?? PD29 -- PIC 10 MHz to best sidereal 1PPS, with sync and milli-step

?

?

Note 5: You can also replace the large coil on regular AC mains powered analog clock with a smaller winding and lower voltage.

https://sound-au.com/clocks/motors.html

https://sound-au.com/clocks/ocm.html

?

Mr. Elliot also has a nice circuit for changing 50>60Hz or 60>50Hz to allow clocks from "over there" to work "here."

?

My sister has a hideous French clock she loves, it runs on 50Hz and the ESP circuit and replacing the high voltage coil with a low voltage one made her a happy camper.?

I could have divided 60Hz down to 20Hz, used a PLL with divide by 5 to generate 100Hz, divide by 2, but that was too simple. I wanted to play with the ESP circuit.

?

?

I'm ignoring Raspberry and Ardino because I have zero familiarity with programming or interfacing them (and no desire to learn, I ignored Apple and Wang at work and they went away....). Although I am running a Raspberry with a dirt cheap SDR from SDRplay and it is nice. A friend's daughter say the Raspberry up for me.

[ The windows version requires windows 10, ain't gonna happen, I'll learn Linux first.]

?

I have enough real electronic projects to keep me busy as long as I'm on this side of the grass.

?

Yea I have too much time on my hand this winter.

The only good thing about winter is it does end. [I hope]

?

?

?

?
Re: ?My Temperature Probe melted

 

¿ªÔÆÌåÓý

Simple logic would suggest 10k +/- 2K

Tony
?My Temperature Probe melted

 


Amazon offers:
10K Temperature Sensor Probe ? I found one even cheaper on TEMU.

The WTESKE Manual says: Type of temperature probe R25 = 10K ohms +/-1% B25/85=3435K+/-1% It is a two-wire probe.

Before ordering, I thought it might be prudent to check to see if the controller had been damaged when the original probe melted.? When the probe is removed, the display blanks out - Open Circuit.? So, it would appear that some resistance is required for the display to indicate the current temperature.

Question: ?What value of resistor might be needed to fool the controller into thinking there was a working R25 = 10K ohms +/-1% sensor installed?


--
G.T.
upgrading PI controller into a current driver for a YIG

 

There is a PI controller with certain AC behavior. I need to use this PI controller in order to drive a coil (current controlled oscillator) of 1.5 ?H inductance. For DC behavior at 10 mV input I need 50 mA current on the coil at most. PI controller has proportional and integrator property.

How can I convert this behavior into a driver circuit?

/g/electronics101/photo/296358/3878514?p=Created%2C%2C%2C20%2C2%2C0%2C0

/g/electronics101/photo/296358/3878513?p=Created%2C%2C%2C20%2C2%2C0%2C0
Re: Charging Circuit

 

Found many variations of 2/3 AAA NiMH in multi packs on Amazon. Both button top and tabbed. It does appear that 300mA is harder to find. Going to next step in capacity, 400mA, yields better results.

~SD
Re: Charging Circuit

 

For kicks and grins I sent an email to Sabre to ask if I could purchase a replacement battery. Their response was " The battery is non-replaceable". I replied that I already had the unit apart and commented on the ack of overvoltage protection on the charging circuit. Since I had it apart I again asked for a replacement. Again they said NO and also said they would forward the comment on the overvoltage issue to their quality department.
So much for customer support. I did see the Ali web site had 2/3AAA 300 maH batteries for less than $2.00 with a shipping cost of $6. Delivery in mid March!
I think I'll just pack it up and give it back.

Dan
On Friday, January 17, 2025 at 08:07:02 PM EST, Mike via groups.io <niche@...> wrote:


Interesting thanks,
Ive had few nicads & LiMH pretty much similar issues you've observed and incl trying to perturb them enough (incl slap then hard to break up shorting crystals)? to take a charge but, for my applications Li Ion's higher density more applicable and more efficient time/cost wise.
?
From my observations of how duralamin was found/produced Ive experimented with putting dead or failing Li Ion's in the freezer until they reach same temp approx -15C etc then taking them out until they get to ambient then back into freezer so these cycles repeated over a few days - whilst Not charging or discharging avoiding catastrophic failure - though have trickle charged frozen Li Ion couple of times no issues so far, though would only be comfortable doing this outside in a bucket of sand with a scoop of sand at the ready...

Only after those cycles on charge at ambient temp observing charge current and rate of change of cell voltage.
?
Would be good to find/design a battery cell characteriser - which reports Eg internal resistance, change in cell voltage when not charged/discharged in relation to temperature, efficiency re power not just Amp Hrs, proclivity to overheat ie temp stats during charge/discharge - so as to produce
some reference metric then serialise ie barcode stick on side of battery to track it with attention to cost/time etc
?
I wonder how it would go to subject the battery to ultrasonics when charge/discharge eg to influence internal chemistry mobility etc.
?
Extending the above to earlier nicads would be of interest though Id focus on large commercially useful packs, those for research could be worth it also as tool for education high school/uni etc
Re: Charging Circuit

wn4isx
 

Want to think about fireworks....
?
https://www.cnbc.com/2024/09/13/tesla-semi-fire-needed-50000-gallons-of-water-to-extinguish.html#
?
My brother in law was trapped on the interstate for an hour or so before CHP was able to have everyone behind him turn around and drive the wrong way to the closest exit. He told me he was probably 500 feet away and standing outside his car he could feel the heat.
?
I'm not sure the 50,000 gallons of water had any real effect or if it just took 15 hours to consume all the lithium.
?
There was (?is?) a massive fire at a lithium utility backup center
?
I so want an electric vehicle with lithium batteries. [not]
?
And I can't wait to add a Tesla power wall.
[So not gonna happen!]


?
Re: Charging Circuit

 

¿ªÔÆÌåÓý

As a teenager I bought pure lithium metal.? It was supplied in a jar covered by oil.

I cut off pieces and threw them into snow or ice for instant fireworks.

Bertho

?

?

From: [email protected] <[email protected]> On Behalf Of wn4isx via groups.io
Sent: 20 January, 2025 12:11
To: [email protected]
Subject: Re: [electronics101] Charging Circuit

?

Trust me, I took enough chemistry in college to know lithium and water react rather violently.

But no one was listening to me when the phone went up in flames and someone grabbed a child's squirt gun and 'zapped' the phone, instant flare up and another person used a paper plate to push the phone in a cooler filled with ice and water.

The ice might have slowed the reaction a bit...then again not enough to matter.

?

Instant cloud of steam and flaming bits of plastic.

?

By cloud of steam, I've played with smoke grenades, legally in college, and the wall of steam was at least as large as a typical military smoke grenade cloud.

?

But all fires end when the fuel is gone.

?

One good thing was the phone melted the bottom of the cooler, which let the water out, which put out the small grass fire the flying flaming bits of whatever started.

?

The best part was the fire department....I simply sat there, kept my mouth shut and let others explain what they'd done and why as they "grilled" us.?

?

At least the food wasn't harmed.?

?

The city was very unhappy because the phone left a deep burn scar on the picnic table...I guess they complained to Samsung.

?

If it had been up to me, I'd have knocked the phone to the ground, called 911 and then used water in the cooler to put out the inevitable grass fire and let the phone burn itself out.

?

I view our lithium battery powered equipment as "incendiary devices in waiting."

?

?
Re: Charging Circuit

wn4isx
 

Trust me, I took enough chemistry in college to know lithium and water react rather violently.
But no one was listening to me when the phone went up in flames and someone grabbed a child's squirt gun and 'zapped' the phone, instant flare up and another person used a paper plate to push the phone in a cooler filled with ice and water.
The ice might have slowed the reaction a bit...then again not enough to matter.
?
Instant cloud of steam and flaming bits of plastic.
?
By cloud of steam, I've played with smoke grenades, legally in college, and the wall of steam was at least as large as a typical military smoke grenade cloud.
?
But all fires end when the fuel is gone.
?
One good thing was the phone melted the bottom of the cooler, which let the water out, which put out the small grass fire the flying flaming bits of whatever started.
?
The best part was the fire department....I simply sat there, kept my mouth shut and let others explain what they'd done and why as they "grilled" us.?
?
At least the food wasn't harmed.?
?
The city was very unhappy because the phone left a deep burn scar on the picnic table...I guess they complained to Samsung.
?
If it had been up to me, I'd have knocked the phone to the ground, called 911 and then used water in the cooler to put out the inevitable grass fire and let the phone burn itself out.
?
I view our lithium battery powered equipment as "incendiary devices in waiting."
?
?
Re: Charging Circuit

 

Chemically, Lithium is very reactive to air and water. Hence, water is NOT a good method to put on a Li-ion fire.
Re: Charging Circuit

 

Roy,
I have quite a bit of association with LiPo batteries. I fly RC aircraft and LiPo's are the preferred power source. Many times there are articles of flyers charging their batteries and having them catch on FIRE. So much so that there is a combination charging bag and metal container as a charging fire suppression mechanism.
As to the bad cell in my 4 pack of NiMH, I placed in the freezer for a day and let it return to room temperature. Using my old Power Designs power supply I was able to pump in about 50 ma but the cell started to heat up. It took about 35 volts to get that 50 ma. I returned the cell to the freezer and I'll let it stay for a day and try again.
Looking for a 2/3 AAA 300mAh battery has many suppliers but who wants to pay almost $9 for a single cell. Not replacing all four cells seems like a bad engineering decision since the device is over 5 years old.
I am still not convinced the charging circuit is optimum for these cells. There is no overvoltage protection and relying on the capacitive reactance as a limiting device is a stretch.

Regards,
Dan
On Saturday, January 18, 2025 at 12:03:23 PM EST, Roy J. Tellason, Sr. via groups.io <roy@...> wrote:


On Friday 17 January 2025 12:35:23 pm wn4isx via groups.io wrote:
> As I've said, I really distrust and dislike nicads....except for the big ones rail road companies used at crossings.

I had a bunch of them a while back,? and eventually gave up on them completely.? The lower terminal voltage was an issue,? and they just didn't seem to reliably hold a charge.

> NiMH are much better behaved but a @itch to charge.

Had some of those,? too,? and gave up on them.

> Lithium Ion are better energy density wise, but draw too much current or charge wrong and you have an instant incendiary grenade.

I bought a bunch of those TP4056 modules,? and use those.? There are a couple of variants out there,? I got the ones that have the protection on the board as well as the charge control.? So far they've worked out pretty well with a bunch of cells salvaged from laptop batteries.? I had several of those,? and when you open them up there's typically only one or two cells that are bad.? The one thing that didn't work out well was putting one of those setups into a chinese dremel clone,? I'd need to find me some higher-current cells to use in that application.

> A friend had one of the troubled Samsung 'catch on fire' phones and his went up on a picnic table.
> It was a bit too exciting. Hint, do not use water on a lithium fire, that made it more exciting. And knocking it into a bucket of water was beyond exciting.
> Think "Extreme thermal event."

My first smart phone was a Samsung.? I won't buy another one,? not after those stories hit the news,? particularly.? They were just flat out irresponsible.

My last phone got interesting.? I'm not sure what I was doing wrong in my charging regimen,? but the battery bulged enough to pop the case open.? I eventually procured another battery and installed it,? but apparently damaged some other stuff in the phone so the speaker didn't work any more,? and I'm not sure what else.? The little board at the bottom of the phone wasn't available,? so I'm out the $20 I spent on that battery and the phone got replaced.

The battery got removed and placed in a metal bucket with sand in it,? until I took it to recycle at Lowe's.? Interestingly enough,? their recycle box is outside of the store...

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Re: Charging Circuit

 

On Friday 17 January 2025 12:35:23 pm wn4isx via groups.io wrote:
As I've said, I really distrust and dislike nicads....except for the big ones rail road companies used at crossings.
I had a bunch of them a while back, and eventually gave up on them completely. The lower terminal voltage was an issue, and they just didn't seem to reliably hold a charge.

NiMH are much better behaved but a @itch to charge.
Had some of those, too, and gave up on them.

Lithium Ion are better energy density wise, but draw too much current or charge wrong and you have an instant incendiary grenade.
I bought a bunch of those TP4056 modules, and use those. There are a couple of variants out there, I got the ones that have the protection on the board as well as the charge control. So far they've worked out pretty well with a bunch of cells salvaged from laptop batteries. I had several of those, and when you open them up there's typically only one or two cells that are bad. The one thing that didn't work out well was putting one of those setups into a chinese dremel clone, I'd need to find me some higher-current cells to use in that application.

A friend had one of the troubled Samsung 'catch on fire' phones and his went up on a picnic table.
It was a bit too exciting. Hint, do not use water on a lithium fire, that made it more exciting. And knocking it into a bucket of water was beyond exciting.
Think "Extreme thermal event."
My first smart phone was a Samsung. I won't buy another one, not after those stories hit the news, particularly. They were just flat out irresponsible.

My last phone got interesting. I'm not sure what I was doing wrong in my charging regimen, but the battery bulged enough to pop the case open. I eventually procured another battery and installed it, but apparently damaged some other stuff in the phone so the speaker didn't work any more, and I'm not sure what else. The little board at the bottom of the phone wasn't available, so I'm out the $20 I spent on that battery and the phone got replaced.

The battery got removed and placed in a metal bucket with sand in it, until I took it to recycle at Lowe's. Interestingly enough, their recycle box is outside of the store...

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Re: Charging Circuit

wn4isx
 

On Fri, Jan 17, 2025 at 08:07 PM, Mike wrote:
I wonder how it would go to subject the battery to ultrasonics when charge/discharge eg to influence internal chemistry mobility etc.
I suspect it'd take quite powerful ultrasonics to break up the 'whiskers' that grow in the electrolyte.
I never considered freezing, I'll pass that idea on to ham friends who still fight with NiCads.
Re: Charging Circuit

 

I'll try the freezing process and see what happens.
Thanks,
Dan
On Friday, January 17, 2025 at 08:07:02 PM EST, Mike via groups.io <niche@...> wrote:


Interesting thanks,
Ive had few nicads & LiMH pretty much similar issues you've observed and incl trying to perturb them enough (incl slap then hard to break up shorting crystals)? to take a charge but, for my applications Li Ion's higher density more applicable and more efficient time/cost wise.
?
From my observations of how duralamin was found/produced Ive experimented with putting dead or failing Li Ion's in the freezer until they reach same temp approx -15C etc then taking them out until they get to ambient then back into freezer so these cycles repeated over a few days - whilst Not charging or discharging avoiding catastrophic failure - though have trickle charged frozen Li Ion couple of times no issues so far, though would only be comfortable doing this outside in a bucket of sand with a scoop of sand at the ready...

Only after those cycles on charge at ambient temp observing charge current and rate of change of cell voltage.
?
Would be good to find/design a battery cell characteriser - which reports Eg internal resistance, change in cell voltage when not charged/discharged in relation to temperature, efficiency re power not just Amp Hrs, proclivity to overheat ie temp stats during charge/discharge - so as to produce
some reference metric then serialise ie barcode stick on side of battery to track it with attention to cost/time etc
?
I wonder how it would go to subject the battery to ultrasonics when charge/discharge eg to influence internal chemistry mobility etc.
?
Extending the above to earlier nicads would be of interest though Id focus on large commercially useful packs, those for research could be worth it also as tool for education high school/uni etc
Re: Charging Circuit

 

Interesting thanks,
Ive had few nicads & LiMH pretty much similar issues you've observed and incl trying to perturb them enough (incl slap then hard to break up shorting crystals)? to take a charge but, for my applications Li Ion's higher density more applicable and more efficient time/cost wise.
?
From my observations of how duralamin was found/produced Ive experimented with putting dead or failing Li Ion's in the freezer until they reach same temp approx -15C etc then taking them out until they get to ambient then back into freezer so these cycles repeated over a few days - whilst Not charging or discharging avoiding catastrophic failure - though have trickle charged frozen Li Ion couple of times no issues so far, though would only be comfortable doing this outside in a bucket of sand with a scoop of sand at the ready...

Only after those cycles on charge at ambient temp observing charge current and rate of change of cell voltage.
?
Would be good to find/design a battery cell characteriser - which reports Eg internal resistance, change in cell voltage when not charged/discharged in relation to temperature, efficiency re power not just Amp Hrs, proclivity to overheat ie temp stats during charge/discharge - so as to produce
some reference metric then serialise ie barcode stick on side of battery to track it with attention to cost/time etc
?
I wonder how it would go to subject the battery to ultrasonics when charge/discharge eg to influence internal chemistry mobility etc.
?
Extending the above to earlier nicads would be of interest though Id focus on large commercially useful packs, those for research could be worth it also as tool for education high school/uni etc
Re: Charging Circuit

wn4isx
 

NiCads can have some odd failure modes, yours is fairly common, under no load the cell will produce ~1.2V, place any significant load and the voltage drops to zero, and the cell won't take any charge current at any sane voltage.
I've had some success using a car battery and connecting the NiCad cell reversed, Bat V+ to car battery V-,, Bat V- to car battery V+. Just a touch, wear safety goggles, use thick gloves.
Another option is to charge a 100uF capacitor to 160ish volts and connect + to +, - to minus.
I restored an original iCom 2-AT battery back this way and the revived cell lasted a bit over a year before it went total open circuit.
?
There are applications where NiCads thrive, watchman flashlights that are used ever night, charge each cell individually the next day at 1/10, use two sets of NiCads and you can (or could in the 1960s) several years use out of the NiCads.
Our next door neighbor's son was a watchman at IBM and he used this scheme.
?
As I've said, I really distrust and dislike nicads....except for the big ones rail road companies used at crossings.
?
NiMH are much better behaved but a @itch to charge.
Lithium Ion are better energy density wise, but draw too much current or charge wrong and you have an instant incendiary grenade.?
A friend had one of the troubled Samsung 'catch on fire' phones and his went up on a picnic table.
It was a bit too exciting. Hint, do not use water on a lithium fire, that made it more exciting. And knocking it into a bucket of water was beyond exciting.
Think "Extreme thermal event."
?
?
?
Re: Charging Circuit

 

Update on my repair. It's NOT! I replaced the diode bridge and LED and connected the battery after "charging" for about 5 minutes. I stopped when I noticed the battery voltage was approaching 10 volts. Further investigation shows a bad cell in the 4 pack. The open circuit voltage on one cell is 1.12 volts but if I put my power supply across this cell it will not take any current. Even though it has a voltage it must have an open circuit internal to the chemistry.
Trying to replace this 4 pack will cost about $32. A new light/zapper is $34.95 so it is a no brainier that a replacement battery is not worth it. Since I already purchased the LED and bridge for $15, no more investment will be made.

Dan Kahn
On Friday, January 10, 2025 at 01:04:07 PM EST, F1CHF via groups.io <f1chf@...> wrote:


put (upload) the PDF here !

/g/electronics101/files

tks



Le 10/01/2025 6:45 pm, Dan Kahn via groups.io a ¨¦crit?:

Here is a schematic I reverse engineered.
On Friday, January 10, 2025 at 11:01:52 AM EST, Roy J. Tellason, Sr. via groups.io <roy@...> wrote:
?
?
On Friday 10 January 2025 09:53:33 am wn4isx via groups.io wrote:
> In your circuit, the NiCad and LED would normally limit the voltage, although you can easily cook a NiCad to death with 24/365 charging at as low as 1/20 C (C being amp hour) and N cell NiCads have a very low amp hour rating. I suspect it'd be extremely easy to cook them to death.

Yeah,? there is that.? I have a Simpson DVM that uses four fat nicads to power it,? and I'm on my second or third set of them so far.? And they're not in good shape.? The original charger for that was a wall wart that was supposed to put out 7.5V,? fed through a resistor and that's it.? I also have a cordless screwdriver that sits in its stand most of the time,? with three nicads in it,? and they're not holding a charge all that well these days either.

> I'd be tempted to use a wall wart and build a real regulated power supply. The circuit you describe is simple, maybe too simple to be reliable.

I've pretty much given up on using nicads these days,? but if I did I think I'd prefer to use a circuit that would stop charging them at a given point,? coming back on only when needed.? Like those TP4056 modules I use for the lithium cells...

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Re: 3-Phase Motor Question

 
Edited

Low voltage is a parallel star connection. This motor can¡¯t be connected delta. The phase windings are connected in series, only one star point (permanent inside the motor) for high voltage. Interchange any two supply lines to reverse rotation.?
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