Lab LED constant current controller board


Ladvien blogged about his Lab LED constant current controller board project he made using DirtyBoard PCBs:

A little lab controller PCB I’m working on. It centers around four high-power constant current circuits meant to be driven by an Atmega328’s PWM.
I hate working on anything mechanical in dim light; comes from dropping parts down under the engine when working on cars. I’m also pretty particular about my type of light. The “Cool White” or CFLs really bother me. I feel like I’m a bug headed towards a bug-zapper.

I have a few design goals,
1. Warm white is the way to go. I’m shooting for four 1k lumen warm-white LEDs at 12v at ~1A.
2. I’ve a plug for an Arduino Pro Mini (APM). It’s hard to fight the APM when it comes to small footprint and versatility, oh, and price. They are super cheap if you buy them on eBay.
3. I want to make a BLE serial interface using my HM-10. This would allow me to control my LEDs using my iOS devices.
4. The A4 and A5 pins are broken out, this is meant to make the boards chainable using I2C.

Check out the video after the break.

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  1. The long strip LED is pretty interesting… the FastTech part page says 12V 7.2W 84-LED, impressive I must say, is it 28-parallel of 3-series (28P3S)? I have been eyeing these, though not parts with so many LEDs. Just a bit concerned about LED chip matching and longevity…

    I hope we readers of DP can get an update in the future about long-term usage of these lighting parts — will they last for a few years of heavy use? But at least there is 28 strings of LEDs, one can still get a bright light with many failed LED chips internally, but you’d need to adjust the resistor value…

  2. My guess is there is a resistor in series with each set of 3 LEDs, otherwise 12v would be too high. There was an article on hackaday about 100w LEDs (5s20p internally) that showed many problems with the ones from ebay.

    1. Nah, AFAIK these do not have integrated resistors, I’ve only ever seen LED chips embedded inside the yellow phosphor. Hence my concerns about current balancing and lifetime. I’ve seen fluorescent tube replacements or equivalents with many blown LEDs…

      Given the standard of their specs, it’s more likely these are _compatible_ with 12V supplies, the kind used for RGB strips. Assuming 3.6V typical for white LEDs at load, 3S will give 10.8V (this value is mentioned for some other parts) and that will give some headroom for a resistor and/or a linear current controller. Would be interesting to check the actual voltages and currents at rated load…

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