Solar Powered Circuit

[gravymister]

Actually I have a couple more questions to prevent damage to the LED's should I use a resistor to provide current limiting? or would that just put too much of a load on my solar panels?

Also on the topic of LED's, I have about 12 White LED's, If I were to put say 6 of these in the circuit (so you could run either the speaker or the lights) what would be the best setup, to run them in parallel, with or without a resistor?

 

[audioguru]

When the battery is only 3.6V the amplifier draws only 16mA when playing as loud as possible. When the battery is fully charged at 4.2V then the maximum current from the battery might be 30mA.

Maybe the Pringles speaker is supposed to be powered from a 9V battery then its output power will be 0.45W at clipping and it will draw 78mA.

The Pringles Speaker is the end of a Pringles can with a 2.5" speaker, an amplifier, a battery holder and an input cord. It IS crappy, here is a squeaky video of it playing: YouTube - Pringles Speaker...

 

[gravymister]

The Pringles speaker is powered by 3 x AAA batterys, so 4.5v? Yeah it doesn't sound great, but if its only used for a voice based radio station I don't see it being a problem.

 

[audioguru]

I bought a cheap clock radio on sale for $1.25. It sounds awlul but much louder and much better than a Pringles crappy speaker.

 

[carbonzit]

Actually I have a couple more questions to prevent damage to the LED's should I use a resistor to provide current limiting? or would that just put too much of a load on my solar panels?

Either your LEDs already have internal current-limiting resistors, in which case you can just connect them up to DC power, or they don't, in which case you need them (resistors in series). Some super-bright LED units include resistors.

Also on the topic of LED's, I have about 12 White LED's, If I were to put say 6 of these in the circuit (so you could run either the speaker or the lights) what would be the best setup, to run them in parallel, with or without a resistor?[/QUOTE]

If you mean strings of LEDs with external resistors, then it's better to put them in series strings, each series string with its own current-limiting resistor. LEDs don't like being connected in parallel; they can draw different currents, meaning some will be dimmer and some brighter, and in danger of burning out from overcurrent.

If they already have built-in resistors, then wire them any way you please.

Oh, and don't mind Scrooge McAudio Duck: his main function around here is to tell you "Your project sucks!".

 

[audioguru]

"Your project sucks!".
1) It has a very small low power speaker.
2) It has very small solar panels that charge tiny low voltage battery cells.
3) It doesn't have enough power to light 6 white LEDs and not enough to charge a cell phone.

 

[gravymister]

Hmm from what you say they must have built in resistors because in their original setting its 3 white LED's wired in parallel powered by the solar panel/battery and there are no resistors, I've attached a series diagram of the original set up in the keyring so you can see. Unless its just badly manufactured (given the price, possible) and they don't have internal resistors? Are they easily distinguished by eye, can you see the resistor?

@audioguru
1.) The speaker power is sufficient for the application
3.) The solar panel/battery combination already power 3 white LED's each and I'm using at least 3 panels, so in principle they should be able to power at least 9 easily.

 

[gravymister]

Just realised I forgot the attachment.

 

[audioguru]

I just noticed that the small solar panel, tiny rechargeable battery and 3 white LEDs are a keyring. A keyring flashlight is designed to be used for maybe 5 seconds at a time maybe twice each day.

Are the LEDs bright enough to light up anything?
Do they light for longer than a few minutes or if they are dim then maybe for one hour?

 

[ronv]

Since we don't have any current draw for the devices, I'll hazard this guess.
1- Leds 10 ma each, battery life 1 hour. Recharge time 10 - 12 hours.
2- Since the speaker needs 2 lets assume it draws 60ma. So with 3 in parallel maybe 1.5 hours. Same recharge time.
3- Cell phone probably not in the cards.
Basically everything is running off the batteries in the key-chain.

 

[carbonzit]

My guess at this point is that he'll build something using the little dinky solar cells, realize they aren't strong enough, and look for something more robust.

No harm, no foul. All part of the learning process. And better yet, using cheap stuff to learn on!

 

[edman222]

henryfayols, a battery is rated in mAh... not mA. So yes it can supply more then it is rated. As was mentioned by another post, batteries with a 40 mAh can supply 40 mA for one hour, or 80 mA for 30 minutes. This how what many people do in the RC world, they buy a battery rated at 1500mAh, and draw 30,000mAh out of it for a few minutes of "play"...


I agree Carbonzit... perhaps he wanted MORE clarification...

 

[Log2]

I don't have any input, but I noticed that the henry guy did the same thing on my topic, perhaps a mod could warn him or something

 

[carbonzit]

Could be some kind of spambot; they often either copy other people's messages or just post gibberish.

 

[gravymister]

Ok I have an update, and a couple more questions! My friend gave me 8 solar lamps that she no longer wants, they have a similar circuit to the ones I'm using but have an led to detect light (so that they're only on at night). These ones charge 600mAh 1.2v batterys, but only 3 of the 8 actually have batterys. I was thinking how best to utilise these, firstly by maybe disabling the solar sensor, by shorting the detector LED so they can be used all the time at the control of a switch. Also the Solar lamps without batterys I was going to keep all the residual and presumabley regulatory circuitary and charge 2 old phone batterys with them.

The questions I have are:

1.) If I short the light detecting LED will the circuit still charge the battery (because presumably the circuit charges in the day and discharges at night, I want it to charge when its not being used and discharge when I want to use it).

2.) Will I be able to charge these old batterys? Can I overload them? Is there a better way of doing it?

 

[carbonzit]

The thing that detects daylight isn't a LED, it's a LDR (light-dependent resistor). Without seeing the actual circuit, it's impossible to tell you how to disable this function.

Has it ever occurred to you that at some point you're going to be better off buying new components, rather than hacking cheap Chinese crap? Don't get me wrong: I love to hack things and try to use whatever flotsam and jetsam comes floating by me. When I find discarded electronics on the street, I grab them and cannabilize them. But at some point there are diminishing returns to this approach. If you actually want to build something that'll work, you might have to break down and actually buy some LEDs, batteries and such.

 

[gravymister]

It looks like an LED, I thought LED's could be used in reverse as light sensors as well as emitters?

Well I do have some of own components, I'm just a bit inept at designing my own circuits which is why i've been posting on here. If I were to just take the solar panels and LEDs and not use any of the components do you think the attached circuit diagram would work?
I'm not sure how to calculate the resistor value?

 

[audioguru]

Your new circuit WILL NOT WORK:
1) The solar panels are upside down.
2) The battery is supposed to power the LEDs at night but instead it is in series with the solar panels so it cannot power the LEDs.
3) White LEDs need about 3.5V each plus a couple of volts for the current-limiting resistor. But you have two groups of LEDs in series which need a total of 9V and you have only a 3.6V battery cell that drops to 3.0V. 6V is missing.
4) You cannot connect two solar cells in series (3.0V) with three cells in series (4.5V) without causing them to fight.
5) LEDs should never be connected in parallel unless they are all measured then grouped to have identical forward voltages.

 

[gravymister]

Ok I've adjusted the diagram but:

1) In the Garden cell circuit the LED runs off a 1.2v 600mAh battery coupled with the solar panel how does that work???
2.) The LED's are identical so they should have identical forward voltages?

 

[audioguru]

A solar garden light uses a voltage stepup circuit that steps up the 1.2V from a rechargeable battery cell to 3.5V to operate white or colours-changing LEDs. The solar panel is about 2.0V to charge the battery.

LEDs are not physical light bulbs that are all mechanically exactly the same. LEDs are diodes with a range of operating voltage even if they are made by the same company and have the same part number. You must measure and sort them all so that their voltages are the same within a group. Then they can be connected in parallel.