1.5 VDC Pseudocell

This project shows how to build a 1.5 VDC pseudocell to take the place
of an AA sized battery. The mechanical aspect of this project offers the
greatest challenge. The electronic portion utilizes an easy to use LM317
adjustable voltage regulator to convert a 5 VDC source to 1.5 VDC.
(excerpt)
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(Thank you In Advance to readers who alert me to typos and whatnot.)
Danke,
Reply to
Don
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The 317 may not be stable without an output capacitor, aluminum or tantalum.
Does the clock stepper motor use big current spikes every tick?
Really, can't you solder the wires?
Reply to
jlarkin
I think your clock would have been quite satisfied with 1.25 volts, that is about a halve empty battery. A 20 uf elco at the output would be nice tnough.
Reply to
Sjouke Burry
The clock will drift. Eventually it will be so far off the correct time to be useless.
Don lives in Casper, WY. He should have no problems picking up WWVB:
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There are a large number of inexpensive WWVB wall clocks that are large enough to read from a distance. These will keep time to better than a second.
You can even get a kit to convert an ordinary clock to WWVB. Search Amazon.
I use a HTAWI WWVB clock that is 16 inches in diameter. It is easy to read from many feet away. It has 3 batteries and will switch automatically when a cell runs down. I expect it to last 3 years or more and keep perfect time.
Reply to
Steve Wilson
Here is a 20 inch La Crosse WWVB clock for $59.99
Reply to
Steve Wilson
AA Dummy Cell: Add wires and you're done.
Or, buy one that does exactly what you're suggesting:
I'm wondering about your "And its electromechanical action drains batteries far too quickly". How quickly is far too quickly? Do you have any current drain measurements? If not, a pointer to the spec sheet on the clock mechanism would suffice. One of these AA high torque motors? Oh swell. No data sheets.
Notice that they have high torque movements that run on C cells. This one claims to run 3 years on one C cell:
I'm thinking either something is wrong with the mechanism (friction, wrong lube, insects in the gears, dirt, dust, etc). Perhaps your expectations might be a bit much for the clock runtime from a AA cell, maybe you're using cheap batteries, the clock may have a phantom load draing the battery, or the clock motor drops out at too high a battery voltage. Lots of things that might go wrong that a few measurements might highlight.
It might be fun to try running it from a super-cap. Lots of peak current and no self-discharge.
Good luck with the project.
Reply to
Jeff Liebermann
The clock will drift. He needs WWVB. See my earlier post.
Reply to
Steve Wilson
Why not hang a D-cell on the other side of the wall? That would give you battery backup!
Reply to
jlarkin
The clock will drift and pretty soon be useless. He needs WWVB to keep time. The batteries can last up to 3 years. See my pervious post.
Reply to
Steve Wilson
I made one of these but I found out for about $10 Amazon will sell you one in either 1.5/3v/4.5v or 6v with appropriate dummy batteries to fill the holder.
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Reply to
gfretwell
The project's complete and has been up running for a day now. The clock itself is primarily aesthetic rather than scientific. In other words, replacing it is not an option. As it drifts, it'll be easy enough to adjust its hands with a long pole while standing on the floor without dragging out the ten foot ladder. Your followup makes me feel my solution is optimal. Those dummy batteries you mention apparently allow higher voltage batteries to be retro-fitted in a bank of batteries? But the wall clock only accommodates a single 1.5 VDC AA battery. The premade pseudo battery won't work because there's no nearby outlet to plug it into. Besides, it also requires a larger, unsightly hole, to pass either the wall wart or the AA pseudocell through.
Danke,
Reply to
Don
If Don wanted a clock that ran forever, he should have so stated. Although the project notes at: lack any statement as to what he's trying to accomplish, I would deduce that not replacing the AA battery at unspecified intervals is the main problem. You just expanded the project by adding an accuracy problem. Whether this is a problem worth solving is up to Don and his client.
I didn't see any mention of replacing an LR44 batteries, so I'll assume that the clock does NOT have an automagic DST (daylight savings time) feature. There's also something called "auto-set" which is intended for areas with WWVB interference or reception problems: Unfortunately, it looks like the DST feature is run by a tiny LR44 battery, which will probably also need replacement. Therefore if the clock requires resetting the time twice per year, I would assume that accuracy is sufficient between DST resettings to not require a daily WWVB resetting.
The hands on the clock seem to be a little longer than the top of the ladder, or about 14 inches long. Such long hands on the clock might require a high torque drive mechanism. Hard to tell without a size measurement. I couldn't find one that does both WWVB and has high torque. I'm sure they exist, but I can't seem to find one.
Are you suggesting a kit that replaces the existing movement with one that has a WWVB receiver, or some kind of retrofit kit? I found quite a few WWVB clock movements on Amazon. The only retrofit kits I could find were complete replacements of the clock movement.
Nice. I had a cheap ordinary wall clock in my office that ran on a single AA cell for about 15 months. After about 2 years of use, it started to slow down and drain the battery in as little as 4 months. So, I tore it apart, cleaned out the accumulated dirt, re-assembled, and it again ran for about 15 months per AA cell. The bushings that ran the hands don't like dust. I gave it away when I retired last month.
Reply to
Jeff Liebermann
You are absolutely correct. The webpage needs to make the main problem and its solution more explicit.
Danke,
Reply to
Don
He implied so by generating a battery replacement and running wires in the wall.
He is doing this for himself.
WWVB clocks solve the accuracy problem.
The drift is temperature sensitive and usually runs about 15 seconds per month. Eventually it will get so bad the time reading is worthless.
WWVB solves this problem.
Yes, that's how they work.
I used to use a HTAWI, but now I notice I have changed to La Crosse.
They all keep perfect time, even up here near Toronto. You should have no problem in California.
I have been using WWVB clocks for many years. They still work perfectly.
The WWVB clock movement is pretty tightly sealed. I have never had one damaged by dust. Taking the movement apart will destroy it.
Congratulations on your retirement.
I retired about 8 years ago. It is a completely different world. No tight schedules to meet, no customers to argue with, much more relaxing. You can do your own thing, at your own pace.
I never could understand people who retire, then die. I guess they didn't have any hobbies that could keep them busy.
Reply to
Steve Wilson
Your circuit design description states that R3 provides the minimum 10mA load current. Yet the value of R3 is 15k which only draws 0.1mA which when added to the R1/R2 divider current of 1.13mA means the minimum load on the LM317 is only 1.2mA far short of the stated 10mA
You don't even need R3 - just change R1 to 120R and R2 to 24R.
piglet
Reply to
piglet
Excellent! (As always, BTW.) Looks like my worst fear was realized as sloppy discipline allowed a decimal point to slip down from mils to micros. Your hint about how to eliminate R3 is much appreciated too. My approach to technology previously untapped by me is to approach it with caution. And a R2 of hundreds of ohms somehow seemed safe, until you helped me see things clearly in my mind's eye. Anyhow, the perfboard will be quickly rebuilt with correct components. It's mounted on an easily accessed backboard and plugged into a strip connected to the UPS used for the phone system. The last bit doesn't matter much, given how a long pole will be used to correct the clock's drift.
Danke,
Reply to
Don
Thanks Don, you are very welcome.
piglet
Science teaches us to verify.
Reply to
piglet
A long pole risks damaging the clock hands.
A WWVB clock will correct the drift and automatically switch for daylight savings. Batteries can last 3 years.
I like your sig. Much better than doubting. Claude Bernard is an interesting figure and is held as the first scientist.
Actually I think that title should go to Michael Faraday and others from his era.
Quote
"Michael Faraday (born Sept. 22, 1791) was a British physicist and chemist who is best known for his discoveries of electromagnetic induction and of the laws of electrolysis. His biggest breakthrough in electricity was his invention of the electric motor."
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Tesla was credited with invention of the electric motor, but he was a century too late.
Reply to
Steve Wilson
Sure, but you're taking all the fun out of it.
Reply to
Robert Roland
There's a few problems with the suggested off-the-shelf solution. [1]
The most project fun happened last, after piglet (and another at eevblog) suggested 120R for R1 and 24R for R2. (piglet, with my last sentence, it suddenly became obvious to me why you use R to denote ohms. LOL.) Although 120R and 24R certainly work, you may still ask, "Are they optimal?" ROTFL. Let's have some fun and see! First, you set up a system of simultaneous linear equations (details shown at my updated link:
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):
R1 R2
1 -5 0 1 1 150
Then you "plug and chug" the system through octave:
octave:1> A = [ 1 -5;
A =
1 -5 1 1
octave:2> b = [ 0;
b =
0 150
octave:3> r = A\b r =
125 25
Close enough for government work, no? Now, was that fun or what?
Note.
[1] First, there's no nearby electrical outlet to plug it into. Second, it requires a larger, even more unsightly, hole in the wall, to accommodate either a wall wart or pseudocell. The attic's unheated and must be sealed afterward, so the project then creeps into spackle and paint matching.
Danke,
Reply to
Don

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