I’m reading this forum for a while now and thank you all for the information provided. I already achieved to build a custom XML based light with programmable (Attiny13) linear driver (AMC7135).
I wish to build a tail light for my bike which will use a red Cree XP-E. Forward voltage is 2.2v so I’d like to avoid linear driver which will waste lots of energy from the li-ion cell. I’m also willing a programmable driver just like those fantastic Attiny based lienar drivers so I could reprogram it with the modes I use.
Does such a driver exist ? I’ve been looking for it but didn’t find anything.
talk to drjones, he’s working on some really cool code that would be perfect for a red rear bike light. Cheap buck drivers are pretty limited in number and features, plus they’re not really all that efficient. You’d have a lot more options with a linear driver and a diode to drop some of the excess voltage.
My wish is a switching regulator and not a linear one. The diode won’t save energy but help the AMC7135 to dissipate the excess voltage. I already managed to flash an Attiny based linear driver to have cool modes but I now want efficiency.
maybe you could try using lover voltage batteries like lifepo4 or two nimhs and linear driver? i’m thinking 2*aa would be quite enough for a bike rear light
I think this is an occasion where we’ll have to rely on you to find the drivers you want and then tell us It’ll be interesting to see what the efficiency is like too.
It would be worth checking out nickelflipper’s 1A buck boost driver design thread. Average efficiency was supposed to be ~85% based on the spec sheet and he’s very keen to get people to test it. It also uses an ATtiny MCU, although his preference is ATtiny25 due to the extra code space and on board thermistor.
Be sure I’ll post any findings. But as a newcomer in the flashlight driver hobbyist arena, I thought many people would be able to tell me if what I’m looking for does exist at the moment.
I also thought my title and introduction post was clear enough but I should have missed something because you advice me some linear regulators.
I’m an electronic noob (schema design and understanding) but have good solder abilities. If this drivers needs a simple swap between PIC and Attiny and rewiring, I’ll be able to do it.
Do you think the swap is possible or you mentioned that possibility as a way to explore ? Sorry for the dumb question but I can’t figure it out myself :).
Never thought about this: would the standard Nanjg 7135 based drivers indeed be able to drive those red XRE-'s using LiFePo 3V batteries (while burning off a lot less heat compared to Li-ions)? (I have some of them lying around not doing much, and some red XRe's that really want to be abused in a flashlight)
I do look for a effective circuit for my DIY rear bike light. Do you think sandwiching 1 mode boost driver(1.5v to 4.2v) with AMC7135 driver will be efficient?
No probs. If LiFePo4 is considered,then you may have to rework on the battery monitor function.Perhaps disable it. If i’m not wrong LiFePo4 can be discharged safely upto 2.5v and AMC require a minimum 2.7v, add the drop v in driver.Personally I’d go with a regulated driver.
So,can any one chip in on how effective is boost + Linear?
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