*BLF LT1 Lantern Project) (updated Nov,17,2020)

welcome to BLF Malibu, I added you at number 919 on the interest list. By the way, I live just up the coast from the California city of Malibu. I was surprised to see someone from Germany choose that as a user name. :+1:

To potential lantern users and others, I am working on the driver design, which is a 4x7135 design with tint shift for two sets of LEDs. The basic driver is done. Several of you have requested other “features” in the design. I am looking for schematics diagrams of these features to incorporate into the driver as appropriate. The best would be a powerbank feature. Others include a simple cell charger.

For me, I have limited or no access to specialty tools for building this driver. So designs that incorporate ICs or components that required soldering with something other than a soldering iron I can not build and test. If you have access to such tools and are willing to help, that would be great. This is a team effort, and my time and skills are somewhat limited. I have learned a bit of PCB layout specifically for this project, which has been fun. How about you join in on the fun as well!

Wow! Looks like a great lantern. I’m definitely interested.

Wow, the last three folks who have expressed interest in this lantern have done so as new members of BLF. Welcome Richp, you are number 920 on the interest list.

I am number 832 on the list. I have two non-members who I showed the thread to and they are in. So please put me up for two more! Thanks

Got you for 3 total KevinZA1988, your next two numbers on the interest list are 921 and 922.

For the charger, the obvious starting point is the TP4056.

https://lygte-info.dk/review/Review%20Charger%20TP4056%20UK.html

Perhaps other newer chips are better, but the TP4056 is well established, and very inexpensive. If you need more than 1A you can parallel them. 1A is enough for an overnight (or daytime) charge. This lantern, if fully loaded with x4 18650s should last many days on one charge. If loaded with just one 18650 a 1A charge would be a fast charge.

To make it into a powerbank is much more complicated, there are several different incompatible protocols unless it is just to be a very basic charger, and it would also require another connector (unless going USBC). This has been discussed and rejected. Unless you can find an integrated chip that does it all, at a low price.

TBH, it would probably be easier just to fit a generic TP4056 PCB, including connector etc. as a separate board, plenty of space in the head, mechanically superior, easily replaceable when the connector wears out or is damaged. You can buy ten of them for under $2 delivered from China. Just connect it with four header pins.

PS: if you add the battery protection IC then it would also protect the cells from over-discharge.

Search “TP4056 battery protection”

Thanks for your feedback TomTom. My biggest concern about the TP4056, and most charger circuits, is the lack of reverse voltage protection.

DEL was doing the driver board for this project and had a powerbank board designed, but he has disappeared. And his powerbank design suffered from lack of reverse voltage protection as well. Adding a schottky diode is an option, but of course the battery charge goes down by the diode forward voltage. DELs design was quite nice, but also requires a 24 pin surface mount IC which I don’t have the ability to work with for prototyping.

I have considered that if one installs the batteries properly once, having USB charging will eliminate the need for removing and replacing the batteries for charging, which is a good thing.

Take a look at the Microchip MCP73861.

“6.1.1.4 Reverse-Blocking Protection
The MCP7386X provides protection from a faulted or
shorted input, or from a reversed-polarity input source.
Without the protection, a faulted or shorted input would
discharge the battery pack through the body diode of
the internal pass transistor.”

Edit: sorry, appears to be obsolete. I’ll do a little more digging.

Edit 2, see MCP73113 and MCP73871. Also protected from RP.

I daresay there are others.

Why was USB-C rejected? I think it should be the obvious choice. Everything has recently went to USB-C, so it already has wide spread adoption. Micro USB is on it way out, and in just a few years will not be as easily available. Whereas USB-C will be easily found for the next 5-10 years, maybe more. Not to mention that the USB-C cables tend to last much longer. I’ve been using the same two USB-C cables for two years (bedside and car charger). MicroSD would only last 3-9 months for good quality cables, and about 1-2 months for cheap cables.

As far as I remember we already discussed the charging solution a while ago (check page 64) and decided that we want to use USB c and a BQ25895 (datasheet ) charging chip.

I don’t know which planet you live on but here you can still easily get any USB cable, even the big fat type B. Micro USB cables will likely be around for decades.

Perhaps more relevant is that a few years from now, USB-C is more likely to mean one less cable to bring on a trip. But I don’t really care either way and I think either choice will be the wrong one for many people so we might as well just toss a coin.

I did state that there was a design completed by DEL that used the BQ25895. However, I do not have the equipment to solder this part to a PCB for testing purposes. I really like the part and the circuit DEL designed, but am unable to build a prototype. That was part of the reason I wrote this post to see if there were any forum members willing to assist in this part of the project.

If we receive offers for the ability to build prototypes using the BQ25895, then it is certainly still a possibility.

Thanks Tom Tom, I will take a look into those parts. Ok, I took a quick look and they quote reverse discharge protection. I think those are strange words to say the leakage back into the chip is “low” whatever that means. I did not look at those specifications. What I did look at was that if the voltage between the BATT output and the return are reversed, then you exceed the rating of the part, and it likely fails. It only takes once to kill the part.

You can protect against reverse polarity very simply with just a small inexpensive FET. No significant voltage drop (unlike a diode).

Edit: a PFet protection is pretty much universal for automotove electronics, together with a big Transzorb to protect against alternator load dump events (not a torch problem).

I think you mis-remember.

As for using the BQ25895 that’s a mad idea. to benefit from any of the features it has to have a microcontroller to set it up, and I think the firmware required would make the stuff to run the LEDs on the lantern seem trivial.

And it is an expensive part. Very expensive.

Study the datasheet.

This is just a torch/lantern, a simple USB micro to charge it up is all that it needs.

If you want it to be a powerbank, well, it’s possible, but take a look at how they are usually done, a USB micro to charge, and a big clunky (but so reliable) USB A for power output.

USBC is not necessarily the next big thing. And is expensive to implement. I have two devices that use it (a smartphone and a Samsung Galaxy TabPro S. Both of them now have dodgy connectors, only used with the OEM cables, a couple of insertions per day. If the connectors fail completely then I will have no way to get my data out, or even charge them. Not happy.

I also thought we had decided on Usb-C. I am 70 and my eyesight is failing. Up until recently I struggled with multiple different Usb cables trying to find the right one and especially the right orientation. Last year I got a Note8 which has ‘C’ and it has been SO MUCH easier …… I know we usually learn from our mistakes, and I think this would be one, but I am confident BLF L2 will have ‘C’…. if I am still around for it.

@ Tom Tom- Are you saying that the C is more prone to damage than the others? I would think it would be the other way around since usually if there is a problem with a damaged connection it is because users either try to force a wrong plug or try to connect with the plug upside down…… Are the C plugs inferior in quality? If it is a cost issue…… how much more would it be per lantern?

Am i the only one here who dont have any usb-c device? :zipper_mouth_face: