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Hello everyone, I want to build something for my dad. He has a large model lighthouse in his window that needs a light. I want to make that for him. I have very little understanding of electrics and electronics, but I have build a couple of game controllers and keyboards using off-the-shelve switches and programmable micro-controllers. I should be able to follow instructions if they’re simple enough. Here’s what I need to build: 1. An LED light that blinks 2. During nighttime, the light is powered through a battery (cannot use power outlet) 3. That battery charges during the day with a small solar panel My idea was to do this with an Arduino micro pro: put a couple of lights on the controller and have the controller run a blinking lights program. This would also allow you to cycle through modes with a button. This is the easy part that I can do myself. The difficult part is to power everything. I essentially want there to be a battery which is charged through a solar panel*. Further, during daytime, the flow from the battery to the Arduino should be interrupted. Essentially, I’m looking to build a small, solar-powered powerbank that stops putting out power when it’s charging. This is a schematic of what I want to build, and it’s the grey part that I need help with:  Here are my questions: • Can you point me to instructions how to build a safe "solar-powered power bank" for this? • How can I interrupt power output when it’s charging (receiving sunlight)? *My father has an LED gadget that does this but there’s not any kind of protection for the battery, and the entire thing runs at 1,2V, too low for an Arduino.
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Oct 9, 2019 14:50
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| # ? May 5, 2024 20:18 |
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So you probably want to get a small lipo with a pre-made charging/protection unit: https://www.adafruit.com/?q=lipo%20charger They usually have solder pads for power input; just find a panel that matches the voltage input range. Of course, dont let the lipo sit in the sun.
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Oct 9, 2019 21:27
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NIMH rechargeable batteries are forgiving enough you can directly wire a solar panel to a few of them connected in series if you match the charged voltage of your battery pack and the solar cell voltage. If you are dead set on the arduino you could put a diode in between the solar panel and the batteries and sense the solar panel voltage with the arduino to see if it is sunny, but to be honest this sounds like a problem that can be solved with 4 transistors.
Dairy Days fucked around with this message at 00:42 on Oct 10, 2019 |
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Oct 9, 2019 23:02
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AgentCow007 posted:So you probably want to get a small lipo with a pre-made charging/protection unit: https://www.adafruit.com/?q=lipo%20charger They usually have solder pads for power input; just find a panel that matches the voltage input range. I had considered one of these units. There are tutorials on YouTube where people build power banks with pre-built units that come with charge management and battery protection. But maybe this is a little overblown. I wouldn't let a battery sit in the sun directly, but it should be fine to let it sit in a case that's exposed to sun, right? Dairy Days posted:NIMH rechargeable batteries are forgiving enough you can directly wire a solar panel to a few of them connected in series if you match the charged voltage of your battery pack and the solar cell voltage. If you are dead set on the arduino you could put a diode in between the solar panel and the batteries and sense the solar panel voltage with the arduino to see if it is sunny, but to be honest this sounds like a problem that can be solved with 4 transistors. I didn't know that NiMH batteries were easier to work with. I guess then it makes sense that the gadget we have has wires going straight from the solar panel to the battery. A few questions: * To get the 5,5V I want to put a few batteries in series. Do I then need a solar panel that can put out 5,5/6V in order to charge them? How wide are the tolerances typically? * I want to go with the 4 transistors. But what do I do specifically? I think I want the transistors to go between the battery pack and the arduino, with a further connection to the solar panel. If the solar panel voltage goes below a certain (to be determined) threshold, the transistor should close the circuit between the batter pack and the arduino so that the arduino turns on. Is there a name for this thing so that I could look for some examples?
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Oct 11, 2019 13:05
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Lord Stimperor posted:I didn't know that NiMH batteries were easier to work with. I guess then it makes sense that the gadget we have has wires going straight from the solar panel to the battery. A few questions:  To get around 5.5v you would put 4 NIMH batteries in series, for a total charged voltage of 6v that will rapidly drop to about 5 for most of the capacity followed with lowering to around 4v when they are nearly flat, and you would charge them with a 6v panel or some combination of series panels totaling 6 volts. According to google, the regulator on the arduino pro micro in your image will regulate any input voltage less than or equal to 12v on the raw pin down to 3.3v or 5v depending on which version you have, but note that if you want to use the 5v version then you should use more batteries in series to make sure the regulator doesn't drop out at half charge. Also your solar panel can be rated slightly below but never above the charged pack voltage, unless you like replacing batteries. The 4 transistors reference is not a solar switching thing, but an observation that the entire desired effect could be produced with something like 4 transistors and no arduino, maybe like this  There are probably 100 ways to tackle this. I think you could get it down to 2 transistors if you had time to mess around with reverse breakdown. This circuit would give a nice transition between on and off instead of a hard blink, but you would want to play around with values to get it to suit your tastes, and if you wanted to, a low voltage cutoff to protect the batteries could be added with a zener or voltage reference and another transistor. If you don't have parts on hand and/or it seems a little over your head I would recommend you do something like this  Make sure your diode is rated with a continuous current at or above the maximum current the panel can put out, but if you are just using AA NIMH batteries something standard like a 1n4001 or 1n5817 should be fine because you really shouldn't be trying to stuff more than half an amp down that size battery anyway. In your code just check the panel voltage with the ADC periodically. When its obvious the sun is up, you can put the arduino into sleep mode with a watchdog timer to check if the sun has gone down every few minutes or something, it shouldn't draw enough power in the shutdown state to run your batteries down, even if its too cloudy to charge for a few days, as long as your LED is just a standard tiny 20 milliamp job. if your LED is something larger you might want to get some NIMH D cells or something, obviously with a panel that is realistically capable of supplying enough charge during the day time. I'm not sure if the arduino ADC has a built in reference, but something else you might also want to do is sense the pack voltage and not blink the led at night if the batteries don't have enough charge to support it, because the batteries will also be damaged if they are over discharged.
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Oct 11, 2019 22:14
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Easiest way is order a $6 LM3909 from eBay. Follow the extremely simple schematics on the internet and use a few "D" cells. If I remember right, a 6V lantern battery will run a single LED on an LM3909 for 5 years or more. It has a CRAZY low draw. I think the "D" cells would last for almost a year. Just replace the 2 D cells every year or two.
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Oct 16, 2019 20:51
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Slack3r posted:Easiest way is order a $6 LM3909 from eBay. Follow the extremely simple schematics on the internet and use a few "D" cells. If I remember right, a 6V lantern battery will run a single LED on an LM3909 for 5 years or more. It has a CRAZY low draw. I think the "D" cells would last for almost a year. Just replace the 2 D cells every year or two. This is a very interesting idea, thank you for it! It's probably the economical one. I have looked at a few examples, but I think I'm not feeling comfortable with the LM3909. There's a bit of a learning curve that I haven't climbed there. I think I'll gently caress this up when I try to build this. Dairy Days posted:
Sorry for the late reply, I was quite busy (still am  ). My micro pros are the 16 Mhz/5V ones, so I got around making a shopping list with a 6V battery pack and 4,5V solar panel. There are some spares/alternatives/packs in there to be safe. Does this sound good? 
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Oct 20, 2019 21:02
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| # ? May 5, 2024 20:18 |
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Lord Stimperor posted:My micro pros are the 16 Mhz/5V ones I've also seen that the arduino pro micro does in fact have a an internal reference for its ADC which means you can check the pack voltage reliably and enter sleep mode when you don't have enough capacity to run the lights if it's been cloudy for a while, which will be important if you are planning to run this off AAA size cells. You should set this level to be around 1.15 - 1.1 multiplied by the number of cells, and measure it through a resistor divider similar to the one I drew in that crappy schematic because most ADCs are incapable of reading voltages very near to or above their supply voltage properly, and because the ADC power comes from the regulator it will always be below the battery pack voltage. But I think you should really consider ordering some lm3903s and lantern batteries, because it is one of the most easy to work with ICs and what I am describing above is a skill level beyond implementing it. Order several and if you blow one up, you can analyze the circuit you constructed and learn why it was wrong. Dairy Days fucked around with this message at 01:02 on Oct 21, 2019 |
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Oct 21, 2019 00:22
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