I'm trying to repair a set of solar powered garden lights. This wasn't working properly, and so I'm in the process of attempting to repair it. Unfortunately the circuit board was covered with some sort of polymer and I ended up destroying it trying to get everything out. Now I've got to rebuild it, and I think I have a solid plan. I'm hoping that I could get some help and just make sure that I'm going in the right direction before I invest my time and money into it. I also understand that I could just pay $20 and buy a new one, but there wouldn't be any fun in that. Additionally, I'm not certain about all the calculations, so if someone could help me out with them it would be appreciated (I don't expect someone to do the calculations, just give me some guidance as to what to calculate )
Details
=====
- The garden lights have 8 LEDs (5 mm, white, I don't know any other details)
- The lights twinkle
- The solar array recharges two Ni-Cd batteries (1.2V, 900 mAh, standard charge 90 mA) during the day, and uses the battery power at night
- Solar panel gives roughly 2V in direct sunlight, not sure about amps (I believe it's the 55x55 mm panel listed on this website: **broken link removed** - 2.5v, 80 ma, 0.2 W, but I'm not 100% sure)
- There's a light-dependent resistor in the solar panel to facilitate charging
Basically that's what I had, and that's what I want to make, only better. The lights that I had were be very dim at night, and wouldn't last too long before the lights went out (1-2 hours). I would like to have lights that last longer (i.e. 3-5 hours) and be as bright, or brighter.
I've done some research online, as well as looked through some books, and I've come up with 3 different ways to make this circuit. At the moment I'm leaning towards a 555/556 timer, but there might be an easier way.
#1) 555 timer:
Because I have 8 LEDs to light, I was thinking of using a voltage doubler circuit that I found here - http://www.reuk.co.uk/Voltage-Doubler-for-Solar-Battery-Charger.htm. I'm doing this to provide more charging ability to the batteries, and hopefully get them fully charged during a day of full/semi sunlight. Also, I think, this would allow a small voltage from the batteries to light them up.
I'm also thinking of having the 555 timer be astable, and have the LEDs connected so that they will be "sinked" and "sourced" (I don't know if those are the right terms, but I got the information here - http://www.kpsec.freeuk.com/components/ic.htm#sinksource. I was thinking this would make the LEDs twinkle ... 4 sourced, 4 sinked; 4 off, 4 on, etc.
Questions
======
- If I were to sink/source the LEDs, would I need a resistor for them? What size should it be? Where should it be placed? I'm assuming the LEDs are 2V each, so that's 16V going to them.
- If the voltage doubler could put out 16V would there be a need for the resistors?
- How could I connect an astable timing circuit with the voltage doubler, and make it compact enough to fit into the light that I have now? Can I combine them into the same 555 timer circuit, or will I need two 555 timers?
- Can I use a 556 timer?
#2.) Reverse-engineered light
This light is shown in this schematic - http://members.shaw.ca/novotill/SolarGardenLight/circuit4.png. I noticed that there is only one AA battery (not my two), and there is an induction coil as well. Would this be a better way to go?
#3.) Solar light
These two schematics (http://www.talkingelectronics.com/projects/SolarLight/SolarLight.html) are very similar (I think), but again there's only one batter and an induction coil. Is there a benefit to these? Also, this website discusses a lot about oscillations and positive feedback. I don't know much about this, and it seems that this is more of a complex version. I don't know
Basically I'm looking for a relatively easy, but enjoyable way to fix this lamp. I'm a beginner with electronics. I can solder, and have access to the majority of equipment that I *think* I need to fix this. Any info would be GREATLY appreciated.
Bryan
Details
=====
- The garden lights have 8 LEDs (5 mm, white, I don't know any other details)
- The lights twinkle
- The solar array recharges two Ni-Cd batteries (1.2V, 900 mAh, standard charge 90 mA) during the day, and uses the battery power at night
- Solar panel gives roughly 2V in direct sunlight, not sure about amps (I believe it's the 55x55 mm panel listed on this website: **broken link removed** - 2.5v, 80 ma, 0.2 W, but I'm not 100% sure)
- There's a light-dependent resistor in the solar panel to facilitate charging
Basically that's what I had, and that's what I want to make, only better. The lights that I had were be very dim at night, and wouldn't last too long before the lights went out (1-2 hours). I would like to have lights that last longer (i.e. 3-5 hours) and be as bright, or brighter.
I've done some research online, as well as looked through some books, and I've come up with 3 different ways to make this circuit. At the moment I'm leaning towards a 555/556 timer, but there might be an easier way.
#1) 555 timer:
Because I have 8 LEDs to light, I was thinking of using a voltage doubler circuit that I found here - http://www.reuk.co.uk/Voltage-Doubler-for-Solar-Battery-Charger.htm. I'm doing this to provide more charging ability to the batteries, and hopefully get them fully charged during a day of full/semi sunlight. Also, I think, this would allow a small voltage from the batteries to light them up.
I'm also thinking of having the 555 timer be astable, and have the LEDs connected so that they will be "sinked" and "sourced" (I don't know if those are the right terms, but I got the information here - http://www.kpsec.freeuk.com/components/ic.htm#sinksource. I was thinking this would make the LEDs twinkle ... 4 sourced, 4 sinked; 4 off, 4 on, etc.
Questions
======
- If I were to sink/source the LEDs, would I need a resistor for them? What size should it be? Where should it be placed? I'm assuming the LEDs are 2V each, so that's 16V going to them.
- If the voltage doubler could put out 16V would there be a need for the resistors?
- How could I connect an astable timing circuit with the voltage doubler, and make it compact enough to fit into the light that I have now? Can I combine them into the same 555 timer circuit, or will I need two 555 timers?
- Can I use a 556 timer?
#2.) Reverse-engineered light
This light is shown in this schematic - http://members.shaw.ca/novotill/SolarGardenLight/circuit4.png. I noticed that there is only one AA battery (not my two), and there is an induction coil as well. Would this be a better way to go?
#3.) Solar light
These two schematics (http://www.talkingelectronics.com/projects/SolarLight/SolarLight.html) are very similar (I think), but again there's only one batter and an induction coil. Is there a benefit to these? Also, this website discusses a lot about oscillations and positive feedback. I don't know much about this, and it seems that this is more of a complex version. I don't know
Basically I'm looking for a relatively easy, but enjoyable way to fix this lamp. I'm a beginner with electronics. I can solder, and have access to the majority of equipment that I *think* I need to fix this. Any info would be GREATLY appreciated.
Bryan
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