Hello,
I am an electronics novice seeking advice on my current project. I know my way around a wood, metal, or maker shop, and have done my own basic repairs on computers, video game consoles, and the like. But I'm not confident enough in my knowledge of electronics to be sure that my current project is going to be efficient and well-designed. I can make it work on my own, but I'd rather not make something that draws ridicule from experts.
I am trying to make a battery-powered lamp for a desk or bedside table. It will be a box-type lamp that throws light in all directions, bright enough to read by or for mood lighting, but nothing intense. I'd like to power it with rechargeable AA batteries because of their ubiquity, but have the option to use USB power as well. Here is what I have got so far, using some Aliexpress parts:
- A 5V, 5W warm white LED plate with 10 small SMD 5730 chips on it and some little resistors (see attachment)
- 4xAA battery pack with a female USB type A connector (currently using 4x1900mAh Eneloop AA batteries)
- A adjustable voltage regulator set to 4V, at which setting the LEDs draw a consistent 400mA. I currently have one with an illuminated LCD that shows voltage and current, with a pot for voltage adjustment only (picture attached). In the finished project, I would like to use perhaps an LM2596S step-down voltage regulator instead, and just set the voltage using the pot and a multimeter. (I don't know if an LM2596S is a well-known piece of electronics, so please let me know if more information on it is needed)
- The finished project would also have a simple power switch between the batteries and the voltage regulator. For now, the fancy voltage regulator I'm using has its own power button.
So, I've tested this configuration and it works well. The LED is 5V, but I am purposely limiting the voltage to 4V to keep the temperature low (the LED plate gets warm, but no more), to keep the current draw low (I am guessing that AA batteries prefer lower currents), and because the light produced is adequate at 4V. I also assume that this will extend the life of the LEDs (not that they're expensive, but I like the idea of long-life and durability as a design principle).
The lamp runs with an even, pleasing light for 3 hours and 40 minutes before the LED starts flickering and the voltage regulator gives up and goes dark. The starting voltage of each AA battery was about 1.38V, and at the time the lamp gives up, it was down to 1.12V per cell. And these are Eneloop NiMH batteries rated at 1900mAh, but they're many years old and well-used.
The lamp also works fine plugged into any powered USB type A jack on a computer or peripheral like my keyboard, drawing the same 400mA current at 4V.
So, my questions are:
- Is there anything in this configuration that is dumb, unsafe, unnecessary, or inelegant?
- Is my idea to ultimately use a cheap, accessible LM2596S step-down converter a good one? After all, if I want it powered with 4V only, then a 3xAA or 4xAA battery pack or a USB jack will all provide a bit more than 4V, so there's no point in using a regulator that can step up as well, right? Or are there better, more robust options for what I want?
- Am I being silly using a voltage regulator at all? I mean, could this LED unit, which has current-limiting resistors built-in, run fine with only a power switch and whatever voltage a 3xAA, 4xAA, or USB port power source feeds it (probably 5-8V range?), with no downsides except maybe a lower battery run-time than when limited to 4V?
And my most novice question, but not super-important for my project directly:
- If this is a 5W, 5V LED, then why does it not draw anywhere close to the amount of current at 5V (or 4V) that basic electricity forumulas tell me that a 5W LED should? Is 5W just the maximum amount of power it can take if you supply it with voltage somewhere over 5V and make sure it's cooled well?
Please, if there is any more information I can supply to make my questions clearer, let me know. Thank you in advance for any advice offered. It will be appreciated.
I am an electronics novice seeking advice on my current project. I know my way around a wood, metal, or maker shop, and have done my own basic repairs on computers, video game consoles, and the like. But I'm not confident enough in my knowledge of electronics to be sure that my current project is going to be efficient and well-designed. I can make it work on my own, but I'd rather not make something that draws ridicule from experts.
I am trying to make a battery-powered lamp for a desk or bedside table. It will be a box-type lamp that throws light in all directions, bright enough to read by or for mood lighting, but nothing intense. I'd like to power it with rechargeable AA batteries because of their ubiquity, but have the option to use USB power as well. Here is what I have got so far, using some Aliexpress parts:
- A 5V, 5W warm white LED plate with 10 small SMD 5730 chips on it and some little resistors (see attachment)
- 4xAA battery pack with a female USB type A connector (currently using 4x1900mAh Eneloop AA batteries)
- A adjustable voltage regulator set to 4V, at which setting the LEDs draw a consistent 400mA. I currently have one with an illuminated LCD that shows voltage and current, with a pot for voltage adjustment only (picture attached). In the finished project, I would like to use perhaps an LM2596S step-down voltage regulator instead, and just set the voltage using the pot and a multimeter. (I don't know if an LM2596S is a well-known piece of electronics, so please let me know if more information on it is needed)
- The finished project would also have a simple power switch between the batteries and the voltage regulator. For now, the fancy voltage regulator I'm using has its own power button.
So, I've tested this configuration and it works well. The LED is 5V, but I am purposely limiting the voltage to 4V to keep the temperature low (the LED plate gets warm, but no more), to keep the current draw low (I am guessing that AA batteries prefer lower currents), and because the light produced is adequate at 4V. I also assume that this will extend the life of the LEDs (not that they're expensive, but I like the idea of long-life and durability as a design principle).
The lamp runs with an even, pleasing light for 3 hours and 40 minutes before the LED starts flickering and the voltage regulator gives up and goes dark. The starting voltage of each AA battery was about 1.38V, and at the time the lamp gives up, it was down to 1.12V per cell. And these are Eneloop NiMH batteries rated at 1900mAh, but they're many years old and well-used.
The lamp also works fine plugged into any powered USB type A jack on a computer or peripheral like my keyboard, drawing the same 400mA current at 4V.
So, my questions are:
- Is there anything in this configuration that is dumb, unsafe, unnecessary, or inelegant?
- Is my idea to ultimately use a cheap, accessible LM2596S step-down converter a good one? After all, if I want it powered with 4V only, then a 3xAA or 4xAA battery pack or a USB jack will all provide a bit more than 4V, so there's no point in using a regulator that can step up as well, right? Or are there better, more robust options for what I want?
- Am I being silly using a voltage regulator at all? I mean, could this LED unit, which has current-limiting resistors built-in, run fine with only a power switch and whatever voltage a 3xAA, 4xAA, or USB port power source feeds it (probably 5-8V range?), with no downsides except maybe a lower battery run-time than when limited to 4V?
And my most novice question, but not super-important for my project directly:
- If this is a 5W, 5V LED, then why does it not draw anywhere close to the amount of current at 5V (or 4V) that basic electricity forumulas tell me that a 5W LED should? Is 5W just the maximum amount of power it can take if you supply it with voltage somewhere over 5V and make sure it's cooled well?
Please, if there is any more information I can supply to make my questions clearer, let me know. Thank you in advance for any advice offered. It will be appreciated.
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