Solar Power Repeater Revised - Charging Questions

charging a lithium-ion battery. I know that
you can get a 3 volt one that delivers about
450mA for only about 5 dollars. I think Li-on
batteries do not have
memory problems, but there are other
considerations. Also, I have tons of NiMH
AA and AAA cells here. (Oh yeah, I have
some old dead cell phones here, and the
Li-on batteries are probably still fine.)

So, I thought I would just throw that in.

Thanks again,
Bruce, MICRO1690/1700

Ya the Li-Ion does not suffer from the memory (loss of zero point) problem like Ni-Cad's have. And they are lighter, hold more charge capacity for longer periods of time.

As to your charging issue...are you trying to avoid an over-charging issue using the solar panels with a circuit not so complex as an actual charger unit?

The simplest way would be to use a zener diode and a current limit resistor. This forms a basic "trickle" type charger and also keeps the solar cell energy from exceeding a certain voltage which would over-charge the batteries.

The set voltage would be determined by the zener diode. The current limit resistor will limit the amount of current being pumped into the batteries so they are not "shock" charged while connected to the solar panels.

There is also a poor man's way to revive those old Ni-Cad's but it takes a good well regulated and high current power supply (4-8 amps) with both voltage and ampere metering to do so. It works by applying reverse polarity to the battery in short bursts and durations while monitoring the current meter. Unless you have had experience doing this..I advise not to. I have revived tons of Ni-Cad's in the past..made a pretty good chunk of change doing so too! 🙂

RFB

Yup, I am trying to avoid an over charge
situation - would it be an over voltage situation?

That is what I think from my limited knowledge.
One zener or more - how ever many it takes
in series to get the voltage down is what I'm
thinking. Because the charging voltage has
to be less than the battery voltage? Actually,
I really don't know.

I guess the next question is how to calculate
the current limiting resistor's value. Right now,
I am in the office of my second job, and my brain
isn't working so well. Is the easiest way just to
try values of resistance until the current becomes
safe? I know that batteries have recommended
charge currents, so I think this wouldn't be too
hard to figure out.

Radio Shack has a 3 volt li-on battery that can
do about 500 mA (which amazes me considering
it's size.) And the battery isn't expensive. (I think
I said all of this already.)

I'm not thinking clearly about this. And I apologize for
that.

Anyway, any other comments you may have will be
welcome.

I guess I need some coffee.

Thanks again,
Bruce, MICRO1690/1700

Actually you would connect that zener in parallel. It's anode to ground and cathode to the + rail. Then attach the limiting resistor BEFORE the zener so as to limit current flow. The zener will keep that voltage from rising too high during sunlight peaks and the limit resistor will always keep the current flow limited as well no matter how much voltage the cells produce.

3.5v zeners are abundant and will serve the purpose here perfectly. The current limit resistor should start with about 10 ohms at 1 watt. That should be adequate to set a trickle charge rate while the zener sets the maximum voltage that will ever be present to the battery. To avoid reverse current flows, place 1 regular diode (1n4001) in series after the zener, its anode to the battery, the cathode to the zener.

You can also use regular diodes, like 1n4001's in series to develop the voltage limiting circuit, but remember a typical diode has about a .7 volt drop across its wafer, so account for that while you add up the didoes. The zener method is better though. Here is a schematic:

As to the zener diode wattage, a 1/4 or 1/2 will do just fine. An NTE 5006a is a 1/2 watt 3.6v zener. For the 'nit pickies' out there monitoring, the mere .6 volts of the zener will be absorbed through the reverse current diode thus around 2.9 or so volts will be feeding the battery. Also remember, the components will have a tolerance swing, in this case 5% so 😛

Experiment with the limit resistor. 10 ohms is a safe starting point either way you go....again to those nit pickies so heck bent on nth decimal point precision which is only achievable with military grade parts or a darn 3 volt TO-92 case regulator! 😛

RFB

One of my dreams also is becoming a power maker. I am so glad you (Bruce) are working on solar power solutions. The entire discussion so far has appealed to my desire to know more about using diodes, battery technology and everything involved.

In your plan you have already described certain equipment you want to power from solar or from charged battery, so I will make one little question:

Can the power be applied to your broadcast equipment while the batteries are being charged?

Can the power be applied to your broadcast equipment while the batteries are being charged?

Yes. The key is to have the load or drain on the battery less than the drain upon the charge source, this way the battery will always have headroom to supply the load, as well as have the headroom left for when the sunshine turns to night...leaving only the battery source to power things.

RFB

Thanks again, RFB!

I never paid attention to this sort of
thing until I got interested in it for
Part 15 reasons.

Things go slowly here, but I will be
continuing with this.

Thanks again and best wishes,
Bruce, MICRO1690/1700
NANO90.9
QUANTUM13.560

Ha Ha. Very good, I see that.

QUANTUM 13.56 !!!!

Fantastic and great, Bruce. That is neat.

Well Carl, I got the idea from you when
we did The Low Power Hour.

The transmitter does work. It's just an
truncated version of yours. It is just
the oscillator - crystal controlled and is
amplitude modulated. It uses a ham
radio antenna tuner to lop off the harmonics.

I am looking into many other designs. Neil has
given me a lot of really good ideas. It runs good
AM if you just hang a wire off of the oscillator
output. Running 1 or 2 milliwatts, it goes about
1000 feet on my Grundig S-350DL. If you try
to put a tuned circuit on the output of the oscillator,
it FMs very badly.

So this 13.560 MHz transmitter is really just a
yardcaster. When I talk about it going 1000 feet,
what I mean is that the signal at that point is gone.
Way gone.

It goes farther than my FM transmitter, and is
easy to set up and run unlike my AM transmitter.

Until I can manage an expanded design, I am actually
very happy with what it is. It's a great yardcaster.

Thanks again,
Bruce, MICRO1690/1700

You might try adding a small transformer in that modulation circuit to help eliminate the FM'ing, and add a buffer stage between the oscillator and final transistor. The buffer stage will not amplify, but simply provide more isolation between the two stages so that audio currents wont back couple into the oscillator...which causes FM'ing.

RFB

Bruce, I am planning ahead for future Low Power programs, and one I want to do will happen when I finally get my SW transmitter in a metal box and hooked up to an outside antenna. I want to do a dedication program as the transmitter is put into regular service. But here's what I'm getting to. I think on that show I should talk to everyone who also operates at 13.56, so I'd want to talk to you if you would like, and I think there's another one, maybe WILCOM if I recall correctly, who also does 13.56. But right now I don't know when that will be.

Be on the lookout for stories about low power shortwave RESULTS, where listeners actually get the signal out somewhere wherever they are located. There need to be stories about that so we can justify running on shortwave. Most nearby neighbors aren't going to listen to SW, unless you are very lucky.

Most nearby neighbors aren't going to listen to SW, unless you are very lucky.

SW is not like it used to be as is the same with AM. The majority of the audience out there are tuned to either FM, internet or imobile devices.

Although I think its a wonderful idea to promote SW just as much as we promote AM and attempt to revive both mediums, it at most will only attract the die hard DX radio enthusiasts...those of us who were around when MW and SW were the big thing.

Don't get me wrong here, again I think its a wonderful idea and well worth pushing like AM. Realistically, simply due to the new age mediums far easier and much cheaper to the masses to obtain than a good SW DX radio....do not expect a huge following, even locally 1000 feet away.

Fun to play with though. I remember spending hours upon hours slowly tuning that DX radio and notching out them darn buzz saw iron curtain stations to try to squeeze out those distant broadcasts. Listen to WWV for hours too! Tune in to the chitter chatter across the ham bands...listen to the beacons, the fading in and out sky wave propagation characteristics, even come across number stations a lot.

And most everyone thought we were crazy. Bah! 😉

RFB

There is a cosmetic value to everything in the part 15 heart. (that's sounds so poetic that I'm embarrassed)

But think of it. You're having tea with the neighbors, and you happen to drop a few remarks here and there about "Your stations." They don't care about listening, but they do care about knowing someone "important." Yet you don't act important (well, maybe I do, but you don't), and when you add everything into the mix: "Ah yes, AM, FM, there's the International Shortwave station and webcasting on the world wide. Ah, sugar please."

Those neighbors are cell phoners and cable TV or dish TV subscribers. Maybe some FM in the car.

But you have status with your 42 radio stations that nobody hears. And there's talk of a TV station in your future (web camera).

Well thats all well in good, cept one thing....who is sitting at the tea table....the new age thinking or the old fashioned?

Reality comes into play here. I do not think your going to get much attention from the new age crowd with tea....maybe a few 18 packs or perhaps that other type of "green" tea that lets out a peculiar odor...but the reality is that there are so few of us left and we have a huge mountain in our way of new age mediums, very very short attention spans and incredibly fast bored do something else mindsets.

I mean I agree with what your saying Carl, and its viable. However you have to look at both sides of it here and realize that it will take a lot more than a 4 pm sitting at a tea table. I think it will have to include something very appealing to the younger generations that these mediums we are working with are worthwhile and valuable as is their xboxes and cell phone text messages to someone sitting 3 feet distant.

So the question becomes more of telling a few nearby neighbors about what we are trying to accomplish. I actively go around and hand out cards and fliers about my stations, talk to these incredibly loud and sometimes obnoxious bands to tell them there is world out here hungry for your material..submit some music...speak to them and expose them to this media opportunity.

I would like to see an entire network of our stations form and become one powerful force. Strength is in numbers. Fragmented as it is now....the task at hand will be incredibly difficult.

RFB