Repair water damaged Solar Garden Lamp

Why? What makes you think they have failed? Passive components don't often fail unless they are mechanically damaged or show obvious signs of overheating. A DMM will confirm if that is the case. Usually these devices have a couple of small inductors to generate the LED voltage.

Looks to me more like the NiCad has vented caustic electrolyte and a quick wash and brushup followed by swapping the batteries for a new pair will fix it (any pair of AA's for quick functional test).

Regards, Martin Brown

Agree. The batteries don't last in these things.

John

If after cleaning it up and changing the batteries they still don't work. You could just buy new ones Home Depot usually has some on sale every year for a couple of bucks each. I paid five bucks per about 3 years ago and they are still going even after being left out in the winter. My dogs getting older so I leave them out in the winter so he can see better. :-)

I have everything I need here to test and fix them but for 5 bucks I wouldn't waste my time. I would just get new ones unless they just need replacement batteries. The batteries probably cost almost as much as the lights.

. s

They make 1/8th-watt, 1/10-watt resistors, and even 1/16th and 1/20th- watt resistors. All of these are physically smaller than standard 1/4-watt resistors. Digikey carries them.

Not sure what the diode function is (no schematic), but it's probably just being used to isolate the NiCad from the solar cell. (?) If so, I'll bet any diode that fits will (should) work. Maybe a

1N914. They're tiny.

STS is probably the manufacturer. ?? Again, probably just used as a simple switch. So maybe a 2N3904 or

2N3906 would do? Keep in mind these are all total guesses.

Personally, I would put a voltmeter on the solar cell first and make sure there's some output in direct sunlight. Would be a bummer to find the device basically works, but it's not charging itself. And as others have stated, I wouldn't "trust" a NiCad in the garden for too many seasons....

Good luck.

I have had good luck with NiMH cells in the garden, but these types of lamps need constant attention.

Can't tell from the picture how much damage, but water cleans most green stuff away, then protect.

greg

"Dave_s" wrote in message news:Gsygn.53313$ snipped-for-privacy@newsfe12.iad...

I think these lamps usually use a "joule thief" type circuit which can generate the required 3 VDC or so for the white LED from mostly depleted NiCd cells down to 2 VDC or less. But that would indicate a little inductor/transformer, which I don't see in the photos. I made the following "joule thief" circuit which actually regulates the LED current over a range of battery voltages, and I have attached the LTSpice schematic. I actually built the circuit and it drives two large white LEDs in series with as low as 2 VDC, and it's fairly efficient.

What is also lacking is the charging circuit from the photovoltaic cells to the battery. It might be just a Schottky diode.

Some components in the attached circuit may not be required, and values are not critical. If you do a search you may find very simple circuits and even one or two that use a bunch of turns of wire on a nail for the tapped inductor. Maybe you can roll your own circuit as a deadbug and then encapsulate it in electrical grade silicone.

Paul

-------------------------------------------------------------- Version 4 SHEET 1 880 680 WIRE 80 0 -112 0 WIRE 208 0 80 0 WIRE 80 16 80 0 WIRE 208 16 208 0 WIRE 208 112 208 96 WIRE 368 112 208 112 WIRE -112 128 -112 0 WIRE 80 128 80 96 WIRE 208 176 208 112 WIRE 80 224 80 208 WIRE 80 224 0 224 WIRE 96 224 80 224 WIRE 144 224 96 224 WIRE 0 240 0 224 WIRE 96 256 96 224 WIRE 192 304 160 304 WIRE 288 304 272 304 WIRE 368 304 352 304 WIRE 496 304 368 304 WIRE 272 320 272 304 WIRE 496 320 496 304 WIRE -112 384 -112 208 WIRE 0 384 0 304 WIRE 0 384 -112 384 WIRE 96 384 96 352 WIRE 96 384 0 384 WIRE 208 384 208 272 WIRE 208 384 96 384 WIRE 272 384 208 384 WIRE 368 384 272 384 WIRE 496 384 368 384 WIRE 368 432 368 384 FLAG 368 432 0 SYMBOL npn 144 176 R0 WINDOW 0 33 47 Left 0 SYMATTR InstName Q1 SYMATTR Value 2N2219A SYMBOL ind2 96 112 R180 WINDOW 0 36 80 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName L1 SYMATTR Value 800µ SYMATTR Type ind SYMBOL ind2 192 0 R0 SYMATTR InstName L2 SYMATTR Value 100µ SYMATTR Type ind SYMBOL LED 352 240 R0 WINDOW 3 22 69 Left 0 SYMATTR InstName D1 SYMATTR Value AOT-2015 SYMBOL res 64 112 R0 SYMATTR InstName R1 SYMATTR Value 1k SYMBOL voltage -112 112 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 3 SYMBOL LED 352 112 R0 SYMATTR InstName D2 SYMATTR Value AOT-2015 SYMBOL schottky 16 304 R180 WINDOW 0 24 72 Left 0 WINDOW 3 24 0 Left 0 SYMATTR InstName D3 SYMATTR Value 1N5818 SYMATTR Description Diode SYMATTR Type diode SYMBOL LED 352 176 R0 SYMATTR InstName D4 SYMATTR Value AOT-2015 SYMBOL res 352 288 R0 SYMATTR InstName R2 SYMATTR Value 30 SYMBOL npn 160 256 M0 WINDOW 0 33 47 Left 0 SYMATTR InstName Q2 SYMATTR Value 2N2219A SYMBOL schottky 352 288 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName D5 SYMATTR Value 1N5818 SYMATTR Description Diode SYMATTR Type diode SYMBOL cap 256 320 R0 SYMATTR InstName C1 SYMATTR Value 100n SYMBOL res 288 288 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 34 46 VTop 0 SYMATTR InstName R3 SYMATTR Value 1k SYMBOL cap 480 320 R0 SYMATTR InstName C2 SYMATTR Value 10µ TEXT 280 72 Left 0 !K1 L1 L2 1 TEXT -66 360 Left 0 !.tran 10m startup

That is certainly the most common over here. You should not assume the batteries are wired in series though - some of mine are in parallel. I was quite surprised when it started working with only one cell replaced. Adding the second cell in parallel made it brighter. I guess this allows them to save on components with a corresponding loss of efficiency.

In the UK the very long summer twilight makes it worth adjusting the switch on point to much darker than the default manufacturers setting which assumes a latitude of 30 degrees or so.

In winter they die a horrible death outside here alternately freezing and being totally discharged for days on end. The batteries do not like this treatment at all. The ones installed on roadside safety signs like "beware bend" always fail in the worst icy foggy weather.

Regards, Martin Brown

I have seen and messed with a number of "solar garden lights" and they all use a 1n4005 or equivalent to isolate the silicon solar cell from the battery (so battery will not discharge into solar cell). One can use a schottky for slightly better efficiency. Most 2-transistor schemes use an NPN and a PNP to make an oscillator to drive a small inductor that pulses the LED, but some use two NPNs. See if they have exactly the same markings (both NPN),or are different (NPN / PNP). Any generic "small signal" silicon transistors will work. If after cleanup it still does not work,i would suspect that the PCB has adsorbed a lot of alkaline type crud from the batteries..so replacing is best.

Sounds like they'd be causing more accidents than they prevent if people end up relying on them and they don't work when most needed.

Sylvia.

Paul and others,

My Solar Lamp has no inductors that suggest a "Joule Thief" circuit is used. My LED is orange, not white.

I tried to use run your netlist with my LTSPICE 4. Only get error message "multiple instances of SYMATTRIB".

I copied your netlist into NOTEPAD and saved as SOLAR_JOULE.CIR. Can youi suggest what else I can do to run your LTSPICE JOULE_THEIF FILE"?

The pcboard looks full of water damage salts. After cleaning with SIMPLE_GREEN and ALCOHOL, the repaired board does not make the LED turn on. Is the base bias resistors, 15K and 100K setting the threshold for LED turn-on at sunrise?

My schematic is suspicious since there is no current limiting resistor between LED and SOLAR CELL VOLTAGE. They cannot possibly be running the LED directly off the battery without current limiting?

Thanks for all your help. Dave_S

Paul E. Schoen wrote:

There must be a transistor though and it will therefore be current limited by the base input current x gain. Have you traced the circuit board to a diagram and checked the component values and track continuity with a DVM ?

Unless you are really fond of it for sentimental reasons your best bet is to buy a new one or make a joule thief variant from scratch to fit in the same physical space.

Designs using a pair of NiCads will barely light an orange led in series with a transistor - are you sure there isn't a small inductor hiding somewhere? It might look to the untrained eye like a resistor with unusual bands on.

Regards, Martin Brown

If you still haven't found the datasheet for your transistors this may be it if I read the numbers of your picture correctly.

"Dave_s" wrote in message news:hrRhn.4015$ snipped-for-privacy@newsfe07.iad...

It is not a netlist (.cir or .net). It includes graphical information for the schematic and should be saved as ASC. The inductor I used is a Cooper DRQ74-101 which is a 10/40 uH coupled inductor in a 7.5mm SMT package. I have attached a simpler version which delivers about 20 mA into a 6V LED load with battery voltage from 2V to 5V, and 10mA with 1.5V.

I did not see your schematic previously. It does not seem quite right. The first transistor seems to be used to turn off the second transistor when the solar cell is producing current. The large diode is usually used to keep the battery from backfeeding into the photocell when it is dark. It is possible that a second photocell could be used just to detect light, but unless it is just a tiny device it does not seem correct. The 15k resistor should be connected to the photocell, but the 3k resistor and LED should be connected to the battery. The photocells might be connected in series to give enough voltage.

The battery is probably connected through a current limiting device to the LEDs and the photocell. It also needs to be configured so that the photocell charges the battery but disconnects the LED load when it is providing current, and then connect the LEDs to the battery when it is dark.

Here is a link to two circuits for solar powered garden lights:

And here are more circuits, ranging from simplest possible to one that uses a microcontroller:

Paul

====================== JouleThief1.ASC ==========================

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Paul,

Ok, your LTSPICE circuit runs and simulates after renaming your circuit from "*.cir" to "*.asc".

I followed some of your links and will follow them all later.

Your mailnote was 'terrific', loaded with much useful info. My schematic does look possibly wrong and incomplete and I will more carefully recheck and correct.

I just read that it may be common to operate the "LED without a current limiting resistor" due to solar cell voltages being small.

My lamp circuit certainly seems different than ANY of the "Joule Thief" style circuits shown. No where on the visible exposed pcboard are any inductors, transformers or capacitors. Makes unlikely that my Lamps use a "Joule Thief" circuit unless there is another circuit board inside the lamp in the chamber with the solar cells. Frozen Phillips head screws presently prevent me from looking at the exact wiring of the solar cells and NiCd cell wiring and looking for a 2nd circuit board.

I have much work to do and will advise results later. Hope to provice an accurate schematic of my Malibou Solar Lamps.

Many thanks, Dave_s

Paul E. Schoen wrote:

"Dave_s" wrote in message news:wjain.51259$ snipped-for-privacy@newsfe10.iad...

I think some of your resistor values are also wrong.

I made an LTSpice circuit that is similar to what you have. I changed some resistor values to match the components I selected, and to make it work as it should. I used 100 ohm internal resistance for the photocell, and 2.4 VDC for the NiCad battery. I used 2N3904 NPN transistors, and a 30k base drive which current limits the LED to about 15 mA. This corresponds to a Beta of 285, which is about right, but it can vary from 100 to 300, so the base resistor or the transistor may need to be selected. Or you can add an emitter resistor and a couple other components to make a more accurate current limited source.

Try the ASC file and see how it turns off the LED when the photocell comes up to about 2.2V.

Paul

======================= SolarLight.ASC ============================

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I made a regulated version which provides no more than 20 mA to the LED at Vbatt=3.0, 15mA at Vbatt=2.2V, and works down to Vbatt=1.8V at which point the LED current drops to about 1.6mA. But the forward drop on the LED model is about 1.9V at 20mA so it is the limiting factor and the circuit is essentially giving it full battery voltage. It fades away to almost nothing at 1.6V which is dead battery anyway.

This circuit uses the zener property of the LED itself to perform current regulation. There was a discussion some time ago about current regulators and this design was presented.

Paul

=========================== SolarLightCurrReg1.ASC ============================

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