Repair water damaged Solar Garden Lamp
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From: Paul E. Schoen on 27 Feb 2010 17:52 "Dave_s" <group78(a)dslextreme.com> wrote in message news:wjain.51259$qJ.48818(a)newsfe10.iad... > 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 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 ============================ Version 4 SHEET 1 880 680 WIRE 400 32 48 32 WIRE 192 96 -48 96 WIRE 272 96 192 96 WIRE 304 96 272 96 WIRE 400 96 400 32 WIRE 400 96 368 96 WIRE 192 112 192 96 WIRE 48 128 48 32 WIRE 272 160 272 96 WIRE 400 160 400 96 WIRE -48 192 -48 96 WIRE 192 224 192 192 WIRE 192 224 144 224 WIRE 272 256 272 224 WIRE 48 272 48 208 WIRE 80 272 48 272 WIRE 48 288 48 272 WIRE 192 304 192 224 WIRE 208 304 192 304 WIRE -48 384 -48 272 WIRE 48 384 48 368 WIRE 48 384 -48 384 WIRE 144 384 144 320 WIRE 144 384 48 384 WIRE 272 384 272 352 WIRE 272 384 144 384 WIRE 400 384 400 224 WIRE 400 384 272 384 WIRE 400 400 400 384 FLAG 400 400 0 SYMBOL Misc\\battery -48 176 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 2.4 SYMBOL Misc\\cell 400 160 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 84 Left 0 SYMATTR InstName V2 SYMATTR Value PWL(0 0 .1 4) SYMATTR SpiceLine Rser=100 SYMBOL schottky 368 80 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName D1 SYMATTR Value 1N5818 SYMATTR Description Diode SYMATTR Type diode SYMBOL LED 256 160 R0 SYMATTR InstName D2 SYMATTR Value QTLP690C SYMATTR Description Diode SYMATTR Type diode SYMBOL res 176 96 R0 SYMATTR InstName R1 SYMATTR Value 30k SYMBOL npn 208 256 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL npn 80 224 R0 SYMATTR InstName Q2 SYMATTR Value 2N3904 SYMBOL res 32 272 R0 SYMATTR InstName R2 SYMATTR Value 10k SYMBOL res 32 112 R0 SYMATTR InstName R3 SYMATTR Value 30k TEXT -82 394 Left 0 !.tran .1 startup
From: Paul E. Schoen on 27 Feb 2010 20:20
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 ============================ Version 4 SHEET 1 880 680 WIRE 544 32 -80 32 WIRE 128 96 -176 96 WIRE 384 96 128 96 WIRE 448 96 384 96 WIRE 544 96 544 32 WIRE 544 96 512 96 WIRE 384 144 384 96 WIRE 128 160 128 96 WIRE 144 160 128 160 WIRE 272 160 224 160 WIRE 544 160 544 96 WIRE -80 176 -80 32 WIRE -176 192 -176 96 WIRE 384 208 336 208 WIRE 384 240 384 208 WIRE 448 240 384 240 WIRE 384 256 384 240 WIRE 448 256 448 240 WIRE 272 272 272 256 WIRE 272 272 16 272 WIRE 272 304 272 272 WIRE 320 304 272 304 WIRE -80 320 -80 256 WIRE -48 320 -80 320 WIRE 176 336 128 336 WIRE 272 336 272 304 WIRE 272 336 240 336 WIRE -80 352 -80 320 WIRE 384 368 384 352 WIRE 448 368 448 336 WIRE 448 368 384 368 WIRE 128 384 128 336 WIRE 384 384 384 368 WIRE -176 464 -176 272 WIRE -80 464 -80 432 WIRE -80 464 -176 464 WIRE 16 464 16 368 WIRE 16 464 -80 464 WIRE 128 464 16 464 WIRE 384 464 128 464 WIRE 544 464 544 224 WIRE 544 464 384 464 WIRE 544 480 544 464 FLAG 544 480 0 SYMBOL Misc\\battery -176 176 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 2.2 SYMBOL Misc\\cell 544 160 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 84 Left 0 SYMATTR SpiceLine Rser=100 SYMATTR InstName V2 SYMATTR Value PWL(0 0 .1 4) SYMBOL schottky 512 80 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName D1 SYMATTR Value 1N5818 SYMATTR Description Diode SYMATTR Type diode SYMBOL LED 368 144 R0 SYMATTR InstName D2 SYMATTR Value QTLP690C SYMATTR Description Diode SYMATTR Type diode SYMBOL res 128 176 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 0 56 VBottom 0 SYMATTR InstName R1 SYMATTR Value 4.7k SYMBOL npn 320 256 R0 WINDOW 0 43 28 Left 0 WINDOW 3 32 59 Left 0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL npn -48 272 R0 WINDOW 0 39 32 Left 0 WINDOW 3 26 56 Left 0 SYMATTR InstName Q2 SYMATTR Value 2N3904 SYMBOL res -96 336 R0 SYMATTR InstName R2 SYMATTR Value 20k SYMBOL res -96 160 R0 SYMATTR InstName R3 SYMATTR Value 20k SYMBOL pnp 336 256 R180 WINDOW 0 41 29 Left 0 WINDOW 3 34 55 Left 0 SYMATTR InstName Q3 SYMATTR Value 2N3906 SYMBOL res 112 368 R0 WINDOW 0 33 25 Left 0 WINDOW 3 27 85 Left 0 SYMATTR InstName R4 SYMATTR Value 2k SYMBOL res 432 240 R0 WINDOW 0 33 25 Left 0 WINDOW 3 27 85 Left 0 SYMATTR InstName R6 SYMATTR Value 100k SYMBOL res 368 368 R0 WINDOW 0 33 25 Left 0 WINDOW 3 27 85 Left 0 SYMATTR InstName R7 SYMATTR Value 10 SYMBOL diode 240 320 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName D3 SYMATTR Value 1N4148 TEXT -344 320 Left 0 !.tran .1 startup |