Drivers for 445

[oic0]

Everybody seems to think the flex is the best way to go. I'm curious why the microboost isn't a better choice. I've been thinking of using a microboost with a single li-ion. If the flexmod would be a better driver for me, could someone explain why?
Thanks

Microboost can do higher voltages.
Flexdrive can do higher amperages.
These diodes don't need the higher voltages but can use the higher amperages. Choosing the microboost is just limiting yourself. If you arent ever going to go that high it wont matter, but why not get the one that you at least could if you wanted to?

 

[Burnsy]

Hey Jayrob,
Did you also measure the voltage when using the V5 at max current?
I?m just quite confused that most of the peaple here don't give a sh... at the voltage but these diodes can be driven with 3.5V to 5V I think?
And since V*A=W this really is quite of a difference in power...
Or am I missing here something?

 

[BShanahan14rulz]

Microboost can do higher voltages.
Flexdrive can do higher amperages.
These diodes don't need the higher voltages but can use the higher amperages. Choosing the microboost is just limiting yourself. If you arent ever going to go that high it wont matter, but why not get the one that you at least could if you wanted to?

75-400mA buck/boost 5V out
75-800mA buck/boost 3V out
75mA-1.5A 2.0V out with 4.2-3.0V in (li-ion)
A good rule of thumb is that: (Vout (Volts) * Iout (Amps) ) / Vin (Volts) < 1.2

75-700mA boost 5V out
75-500mA boost 6.5V out
75-700mA boost 6.75V out with full Li-Ion battery in
A good rule of thumb to follow for input/output conversion is:
(Vout (Volts) * Iout (Amps) ) / Vin (Volts) < 1.2

What does all this mean? Is the 1.2 supposed to be in amps and refer to the max possible current draw from a powersource, and is it variable depending on your powersource?

From what I can see, it looks like the micro boostdrive will create a higher voltage output with the high current output, but then the Li-Ion battery notes show 75-1.5A 2V for the flex and 75-700mA 6.75V for the boostdrive. Does this mean that at high currents, the flex won't make enough volts for the diode on a single Li-Ion?

Another thing I like about the boostdrive is that it says it shuts off at 2.7Vin, whereas the flexdrive shuts off at 2V. The boostdrive will not overdischarge my unprotected lithiums, which I plan on replacing with unprotected IMR's. I was thinking, though, that I might be able to place a diode in series with the battery to make the flexdrive cut out at 2.7v, but I'd have to consult Dr. Lava, I guess.

 

[jayrob]

Hey Jayrob,
Did you also measure the voltage when using the V5 at max current?
I?m just quite confused that most of the peaple here don't give a sh... at the voltage but these diodes can be driven with 3.5V to 5V I think?
And since V*A=W this really is quite of a difference in power...
Or am I missing here something?

I only tested that current with a V5 FlexDrive and a red test load. Not on the diode....

But I know that at 1100mA's, it works on a diode very well. So I'm guessing that at 1.5 Amps, it will also work...

No, I did not check voltage, but others have I believe. I saw some listings somewhere...

 

[nospin]

Here are all the specs on my 445
again why limit yourself on this diode by going with the Microboost


A140 diode
1.5 amps at diode
4.35 volts
1.6 watts at 5 seconds
1.485 watts at at 30 seconds
2.25amps at 18650 battery
4171 host
405-G-1 lens
Micro flex drive V5
about 35 min on time in 11 days

 

[jayrob]

Wow...

Did you use a heatsink on the 5 pin chip like it says to do in drlava's documentation?

 

[HIMNL9]

What about a very low dropout linear driver ? ..... with 5V FV, a pair of Li-Ion must be enough ..... And, considering the need of a BIG heatsinking, for use these diodes at high powers, a 2-cells host is not a so big problem .....

 

[ReNNo]

There are plenty of 2x18650 hosts that are enough big to hold big heatsink.

But power dissipation is twice as with one Li-Ion and boost driver.
And price can be almost the same.
For example... The cheapest 2x18650 host is about 20USD (Aurora) and two 18650 batteries are about 10USD. (30USD)
Microboost is 26USD, one 18650 battery is 5USD and host is about 10USD (41USD)

Price of bigger heatsink + linear driver can easily affect to overall price and 2x18650 solution can be more expensive and massive and duty cycle will be few seconds more.

It's not worth it.


If we want better duty cycle then we should use big 2x18650 hosts with boost driver.
But adjust it to fit only one 18650 battery, or even better to connect two 18650 batteries in parallel.

 

[HIMNL9]

Uhm, being sincere, i meant current sources, not LM317 based drivers ..... with 7,2V typical voltage of a pair of 18650 cells, and a 5V FV diode, it left a 2,2V to turn in power to dissipate ..... that for a 1A driver, make 2,2W of total power dissipation from the driver alone ..... considering the size of a host needed for have a decently long duty-cycle at 1A, the host body can be used also for dissipate the power from the driver ..... and, using hosts designed for flashlights, the driver board can be designed for optimize the usage of the space and the heatsinking (no need to fit it in an aixiz module, i mean) .....



EDIT: BTW, you have also to considerate the power dissipated from the boost driver itself, and the efficence versus the output current ..... i'm not so sure that the power with 2 Li-Ion cells and a linear driver is twice as one Li-Ion and boost, all considered .....

 

[ReNNo]

I know, it's not as linear driver, but it's still too much.
I own 2x18650 IR laser pointer (based on Lm350) and I can feel that host heats quickly (Aurora).
The same will happen to 445nm build.
Full charged batteries are 8.4V (even under LOAD), if current is 1A then heat dissipation is about 7.4W and that is pretty much heat.

But it can be done, and duty cycle will be better.

We can use LM1117 in TO220 package that can give up to 1A.
When batteries are on lower voltage duty cycle is better.

 

[ReNNo]

OMG

445 posts

 

[nospin]

Yes and on the final output at the diode
I used the pill as a sink

 

[magonegro]

I'm planning on build a labby with a LM317 and a LiPo 2S 7.4v batt. Do I need to put a 2W resistor to the LM317 or a 1/4w resistor is enough? (provided the LM317 is well heatshinked)

Thanks.

 

[Xplorer877]

I'm planning on build a labby with a LM317 and a LiPo 2S 7.4v batt. Do I need to put a 2W resistor to the LM317 or a 1/4w resistor is enough? (provided the LM317 is well heatshinked)

Thanks.

That depends on whether you using the LM317 for voltage reglation or current regulation. Usually they're used to regulate current.

If you want to have the LM317 supply 1.25A you'll need a 1 ohm, 2 watt, resistor.

This is a easy to use calculator for the LM317:
LM317 / LM338 / LM350 Voltage and Current Regulator Calculators

-Tony

 

[jib77]

Has anyone used a LD1085V from ST Micro as a basis for a DDL driver? Just curious because we are using it in a prototype board at work to drive a power hungry RF amp. I might have a spare or two to try it out.

Output: 1.25 to 28V @ 3A
Dropout voltage: 1.3V @ 3A

Datasheet

 

[magonegro]

That depends on whether you using the LM317 for voltage reglation or current regulation. Usually they're used to regulate current.

If you want to have the LM317 supply 1.25A you'll need a 1 ohm, 2 watt, resistor.

This is a easy to use calculator for the LM317:
LM317 / LM338 / LM350 Voltage and Current Regulator Calculators

-Tony

Ok thanks, and yes, it's a current regulated circuit. I just had put the 2W resistor, I figured out that may be required, but wanted to be sure cause this resistor is a huge component, definitely NOT for compact builds I Hope to complete it this night. Hope also tomorrow to keep my two eyes Now seriously, I'm a little scared about this thing. I made some months ago an IR 808nm 1.6W labby and after seeing it working I keep it on the shelf since then. (Couldn't imagine those mariomaster's IR builds :thinking::undecided I really dont need such a powerful laser, but like many of us, I can't resist to own a homemade cheap blue laser. Some weeks ago I was thinking I will never have one of them ever. I am scared, but happy.

Thanks again for your help.