Probably another driver coming soon!

Hey everyone i have been working on a linear driver (LM317) for awhile now. I wanted it to be as small as possible and as inexpensive as possible when i say inexpensive i mean 5$ price and its got reverse polarity protection and voltage ripple protection. small as in about 12mm by 10mm approximately. You can operate this driver from two Li-ion cells (ex. Two 18650's two RCR2's etc..)I have ordered all components and will be assembling a few sometime this week or next week. Assuming all goes well i may need a few people to test them. These should be able to run *any* diode and able to run a 2W 445nm, But there can be any output from 20mA-1800mA. ( For the testing drivers only 120mA, 250mA and 1200mA) heatsinking will probably be needed for any currents above 1.3 Amps but I'm not exactly sure yet.I do not want to take any business away from others here but i only plan on contributing here to help others. This would be a great first time build driver for a great price, or if you are on a bit of a budget it would be a great price.

Let me know if anyone is interested by posting below so i have an idea of how many to build

I will edit this post once the parts and the boards get in to include some pictures with exact measurements and test results. Also edit it to add pricing soon



EDIT: To make this circuit as efficient as possible it will likely stay at 700mA max that way it can stay cool and *more* efficient then driving it up to 1.5 Amps

EDIT: final pricing or these will be as followed 1 FOR 5$, 3 FOR 10$ and each additional after that is 2$ more + shipping ill pay the PayPal fees on orders below 15$.
Hopefully that is a good enough pricing.

-Anthony

What's the planned IC?
(or at least, what's the circuit's dropout?)

I cant believe I forgot to mention that thanks for pointing it out it'll be a lm317 I edited the original post to include it

I've seen so many different designs.

Choosing the right voltage range would benefit you (in sales) , and many of your potential buyers - by using rechargeable batteries that are already on the market.

Just an idea.

Thanks for the idea ill always take everyone's opinion into perspective. This design could be used with 2 rechargeable Li-ion cells and a input voltage of 7-12V (ideal voltages) Eventually I plan on making a boost driver that would work with one battery but I'm still working on that one

-Anthony

No problem.

I am telling you on time

I've seen some nice designs, BUT sellers forgot about right battery solution.

In the end to get most of those drivers buyers must use power supply, or some crazy battery combinations.

Once you say to potential buyer clearly "to get the most of my product you can use XXX battery" you will hit the target.

Thanks for the advise I'm gonna edit my original post as I forgot to mention that
Oops

-Anthony

Good luck with your new product.

Healthy competition is always welcome.
You do not have to apologize to anybody for trying to offer another probably good product on LPF.

You probably won't have much luck hitting high 445 currents with an lm317 and two lithium ion cells. Dropout too high.

Brenner said:

Good luck with your new product.

Healthy competition is always welcome.
You do not have to apologize to anybody for trying to offer another probably good product on LPF.

Click to expand...

Thanks

rhd said:

You probably won't have much luck hitting high 445 currents with an lm317 and two lithium ion cells. Dropout too high.

Click to expand...

Probably not because the lm317 is rated for 1.5 Amps but with a lot of heatsinking or by putting two drivers in parallel it could work

LM317's are inefficient too.. At high currents, Voltage Drop would be 3V+
Current Draw would be massive and batteries wont last..
Just my 0.02
U should consider some other ic's too..

Well, not necessarily. You have to remember, these are linear drivers. Any extra voltage gets converted into heat anyway, so if you're driving a red diode with two li-ion's, you'd be dropping around 5-6 volts anyway. The three volts that are dropped by default just get added into the regulation mix.

Voltage dropout only becomes an issue when your diode's Vf is close to the batteries supply voltage. Then does it drop too much voltage, and not run the diode properly. That's primarily why using the LM317 is frowned upon.

And, I don't mean to be negative, but aren't there enough linear drivers for sale?

We got Moh's, the Ghostdrive, Jib's driver, the Groove driver, ... there's probably a few more.

Where we lack selection is in the switching driver department. And, yes, linear drivers are extremely easy to design, but buck/boost converters can be very easy as well.

I'd like to see more buck converters, more boost converters.... not more linears...

Just my two cents!

AnthoT said:

Probably not because the lm317 is rated for 1.5 Amps but with a lot of heatsinking or by putting two drivers in parallel it could work

Click to expand...

That's not the problem. The problem is voltage. If you look at the datasheet, even at 1.5V, you're going to drop between 2.25 and 2.5V just through the IC. Add to that another 1.25V across the resistor, and you have a voltage drop of 3.5V to 3.75V.

From two lithium ion cells, you might have ~8V under a load. So subtract from that your dropout, and you've got 4.25 to 4.5V to the 445nm diode.

That will probably work for some lower current points on the IV curve of the 445, but it won't work for 1.8A, nor likely even 1.5A. Paralleling two of these doesn't increase the voltage, so it doesn't allow you to unlock higher current points either. You're basically out of luck if you want to use the LM317.

Le Quack said:

Where we lack selection is in the switching driver department. And, yes, linear drivers are extremely easy to design, but buck/boost converters can be very easy as well.

I'd like to see more buck converters, more boost converters.... not more linears...

Click to expand...

Everyone is trying

I'd like an open buck design now too, and we may get there at some stage. It's a slow process though!

This guy has the right mentality though - making more drivers for the forum. I think if there were more open/disclosed driver designs, we'd have more people doing what the OP is doing, except with switching drivers.

The LM317 DDL seems simple now, but at some stage it wasn't, and someone had to say "It can be done!" and show everyone how. If everyone locks up their switching driver designs, then that knowledge doesn't get back into the community to the stage where someone like the OP can do exactly what he has done here I think this thread is a good one (even if I may hate the 317 at this stage)

It doesn't require Open Source to design a viable driver...
Drlavas FlexDrive was not Open Source....and it has been
used and has been a favorite for years in Lasers on many
Forums...


Jerry

lasersbee said:

It doesn't require Open Source to design a viable driver...
Drlavas FlexDrive was not Open Source....and it has been
used and has been a favorite for years in Lasers on many
Forums...


Jerry

Click to expand...

Never said that was required. Did I?