Sort of…
Sort of…
With all the talk lately about saving the enviroment, solar power, recycling and hybrid cars it might make sense to try our hand at alternative power sources for part 15 radio stations.
Some full time FM radio stations are thinking about making the move to alternative power sources. One station has been “Green” for years, K-Taos or KTAO 101.9 fm New Mexico. KTAO transmits with 50.000 watts and feeding power to the station is solar arrays and banks of batteries that generate as much as 32 kilowatts per day.
While my setup isn’t as elaborate as KTAO by any stretch of the imagination we are after all experimental so I started small. I have installed a small solar cell on the back of the Scoche FMT 4 and loaded the battery compartment with two fully charged AAA Nimh rechargeable batteries.
I measured close to 2 volts coming from the solar cell and the (2) AAA batteries are slightly over 3 volts. This might be just enough to keep the batteries charge for more than three days. The batteries alone offer 3 1/2 days of juice for the FMT 4 by themselves. (i got the solar cell from a small dual powered calculator for a $1.00)
The FMT 4 does not offer a way to power it from AC but even if it did, that would defeat the purpose of this experiment.
I plugged the transmitter into a portable am/fm radio set to am 1680 and the transmitter is set to transmit on 87.9 fm. Then I placed the transmitter/radio in a kitchen window that gets exposure to the sun for most of the day. (there are no mods to the antenna)
One thing i did notice was even though the little radio i am using is mono, when i was feeding the audio of 106.7 fm into the fmt 4 there was the effect of a overly sensitive AGC. The sound was rising and dropping as if i was overdriving the audio or riding the controls.
I couldn’t stand that so i turned down the volume on the radio wich seemed to limit this problem but after listening to it more it was still there just not as bad. After messing with the Ramsey 25b i decided to change the small radio to am 1680 and the trouble cleared up.
It might be the FMT was trying to process the stereo information taken from 106.7 fm but didnt have all the information and it responded to it the best way it could. The constant up and down levels were the result of stereo being fed into a mono radio then attempting to make it stereo again. ( that was my best guess anyways)
Basically i want to see how long the Nimh battery’s will last before they would actually need to be placed back in the charger.
Now time will tell if this little mod will fail or not. I’ll offer pictures later.
Im pleased to see that this little transmitter has offered us something to work with for so little and from the looks of it, this has to be the longest running thread ive seen for awhile.
As always, keep rockin!
Great info, two observations
The charging capacity of the solar cell might fall a bit short of your needs, as the solar cell needs to deliver a certain number of mAh when sun is present – the solar cells I was looking at in my “thought experiment” on solar power looked like perhaps a 3.6 volt, 100 mA/h panel. It will be fun to see how your test turns out, I might have overestimated the power needs, too.
I didn’t see mention of a blocking diode in your circuit to prevent battery discharge throught the solar panel in darkness and all of the schematics I’ve seen for a solar charger really emphasized that. Two circuits I see a lot are here, from the UK and here from Forrest Cook.
The diode (usually a 1N4001 or 1N5818) is connected like this:
And yes, I agree, best comment thread in quite a while 🙂
Failed but not discouraged
So that one small cell was not enough. Which is what i kind of figured.
The small solar cell from the calculator wasnt enough and judging by the small button cell battery in the calculator I knew it wouldnt work.
I did not install a blocking diode only because i figured the cell wasnt enough to keep the batteries going longer than three days.
Here in Kentucky we haven’t had enough sun either for the past few days its been partly cloudy except for the 3rd of july, it was sunny but i had already disassembled the solar cell from the FMT 4.
My wife is wonderful and while she may not have direct contact with my hobby she has been a contributor the whole way.
She set out to find solar cells that would accommodate my project because she is very much like me and would like to see this solar powered radio station work.
She found a great set of mini solar panels made to charge cell phones and ipods. We ordered two.
Here are the specs:
Work for MP3 MP4 players or cell phones with 3.6V built-in rechargeable battery
Built-in USB 2.0 interface
LED indicator
Solar battery: 0.4 w
Output voltage: 5.1V
Dimension: 73 (L) x 38 (W) x 12 (H) mm
Weight: 28g
Color: white
With a little work I should be able to modify this to work for my needs.
So this experiment is on the back burner until the solar cells arrive.
Another good place to look is Walmart, ugh. I am not crazy about this store and hate to sound as if i am plugging the super center.
At any rate, the lawn & garden center has solar powered patio lights for $4.00. Not a bad price if you don’t mind hacking a perfectly good light. lol
Until then Keep Rockin’
Ohm’s law says that just might do it
5.1 v and .4 W means .078 Amps or 78 mA and I figured 100 mA for just a few hours of sun per day. I’m in the Pacific Northwest, so I only allowed for 5 hours of sun per day 🙂
Figuring Solar Power..
The most accurate way would be getting a current reading directly from the unit while it is in operation.
Insert a current meter in between the battery and the unit and get a reading. Multiply that by 24 and that is what you’ll need to produce (in current) with solar in a 4 hr. period. (10 am ’till 2 pm.. Peak charge time)
There’s a problem charging the battery while using the unit. NiCad batteries require a higher voltage while charging then the designed operating voltage. I’ve monitored cell voltage while in a charger and the voltage level can go as high as 3 volts per cell! If you try to get NiCads fully charged in the unit, you would have too much voltage for the unit to handle. If you don’t have this higher voltage to the battery, the cells will never achieve full charge.
What about NiMH rechargeables?
I have serveral of these batteries and have been able to operate the FMT 4 transmitter a total of 3 days and 2 nights before they needed recharging.
That’s non-stop broadcasting until the led is so dim it is about to wink out.
Eventually, i would like to see if it’s possible to operate the Talking House transmitter and mixing board from a combination of solar panels, charge controller, power inverter and a heavy duty battery of some sort.
I’m sure it’s possible lol , it would be great to know that in some small way i was helping the environment and most importantly my wallet.
When I am not making changes to Zararadio or tweaking the sound I make it a habit to turn off the monitor. I am always going behind my kids and turning off lights and other appliances. 4 out of the 5 kids here seem to think electricity is free. lol.
Think 12 volts..
Most solar equipment of any quality is geared around 12-24-48 volts commercially. If you had one of these, you could operate the device from a 12 volt supply.. (check product details)
http://www.walmart.com/catalog/product.do?product_id=10746815
That 3 volt setting would work just fine. A small lawn tractor battery and a small solar panel like this would run that unit for ever..
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=44768
Green update
Ok so the solar panels i mentioned were in the mailbox for a few days which tells you how often i go to the mailbox. Lol
The panels do exactly what they are supposed to, unfortunately i got them out of the mail a little late so there wasn’t much sun for me to test them properly with a meter.
However under incandescent lights (60 watt bulb) it did show it was working via the power indicator led on the panels.
Tomorrow i hope to test the panels and post my findings here with pictures.
solar wont charge Nimh
I have two AAA nimh rechargables and a solar cell phone charger powering my FMT -4.
The solar cell phone charger is not keeping the batteries charged.
There was some pitiful instructions included with the charger but they only state that the charger delivers 5 volts and for faster charging place solar charger in direct sunlight. (duh)
A digital volt/ohm meter actually showed the charger was delivering around 7 volts in direct sunlight. So I think that it takes quite a bit more juice to charge Nimh batteries and this set up wont do the job.
It might offer a trickle of power to the batteries but so far i dont see this setup keeping the batteries up for longer than a day if even that.
Does anyone know what it takes to charge Nimh batteries? I checked the owners manual for a wall charger that came with these batteries but it really doesnt offer much help.
I have not tried using two of these solar charges together but i dont think that will work either. The solar charger does have a circuit to prevent over charging.
Something else to consider here wich has been mentioned in this thread by 12voltman. Go with a larger scale system including a larger solar panel in the 12 volt range coupled to a 12 volt battery, a charge controller and then step down voltage adapter that converts 12v to 3v for powering the FMT- 4. (a bit too expensive for me) but it would work.
I dont know at this point what my next step would be.
Any ideas?
NiCADs might be something to try
I had read that NiMh are more difficult to charge and that they require a high initial voltage to start the recharging process.
Similarly, I’ve seen NiCad used in the little low power home made plans I’ve seen.
So, perhaps switch to NiCad.
I may try NiCad
I was afraid of that.
Today was a crummy day for testing solar but half the day had sunlight and now as i type this we have reports of severe thunderstorms so i guess that rules out any more testing right now lol.
But so far all the testing i have done with Nimh cells have failed so I might give NiCad a try.
I have to go for now, the wind just blew our propane grill across the porch! lol