Recommend a Direct Drive MOSFET for a single lion cell driver

Flashlight Modding and DIY Parts
41

An oven or hot air would be great :smiley:
Paste is a must, it makes reflowing so much easier.
I think I will just put the board on my emitter reflow = piece of copper, since the opposite side will be clean of any components. Hoping it will heat through the PCB board to the other side.

Hot air, hmm, only have a big air gun, not sure that would not make the components or even the driver fly away.

If none works, Iā€™ll just solder the darn pads with a soldering iron. Thatā€™s another possibility, heat up individual pads and make the paste solder.

Whatā€™s it doing? Replacing all 7135s with a mosfet that will switch the current the same way, but with almost unlimited current through it and minimum voltage drop. Direct driving what ever you connect to it.

Are there direct drive drivers? Maybe, some, havenā€™t heard of a good one that can be reprogrammed.

42

Reflowing on a piece of copper should work well. The heat does get to the topside of a pcb ok. What heat source do you use, stove?

Lots of people do reflow like that, referred to as ā€œhot plate reflowā€. And you can do it anywhere with minimal tools. Iā€™ve used a kitchen meat thermometer to keep an eye on the temp, avoid burning components. Iā€™ve done nanjg 105c drivers, remove bottom components, hotplate reflow the topside. No problem :bigsmile:

43

I use a butane torch, with a catalyst tip adapter so no fire comes out, only hot air.

44

How well does it work for you? Would you know the brand/model you have? Built-in igniter?

I read a bunch of reviews that claim various problems. Hard to light, keep lit, junk models. Reviewer could just be a tool idiot tho. Better looking ones seem a bit costly for what it is. So it makes you wonder if it would be better to just go for an inexpensive temp, flow controlled hot air station.

45

http://www.bernzomatic.com/item.html?id=43

Despite what it says there it doesn't have an igniter, have to use a lighter. But with the catalyst adapter thing it's impossible to blow out as there is no flame. There's a spring loaded shroud that exposes a little ignition port, you light the flame and let it run for a few seconds, then release the shroud and the flame goes out, and the catalyst then burns the fuel.

The catalyst torches are common in jewelry making and the like, there are fancier models with self-igniters but of course, for more money (http://www.solder-it.com). Mine was just what happened to be on the shelf at the local Lowe's.

46

I have a Solomon SL-30, looks like this. It has 50W and reflows emitters or copper blocks fine. Good to know that itā€™s possible to reflow the other side of a board, I havenā€™t tried that yet, havenā€™t had the need to.

I donā€™t do anything on the stove or oven. No electronics in the kitchen for me, I cook there, not solder.

47

SiR4242DP works well, as PPtk suggested it and probably works well for him in his applications.

Had a bad layout before, removed old links to not confuse someone.
Was shoring source and gate. Vishay shows bottom view of the part, not top viewā€¦
For surface mounted parts, I donā€™t know how that is useful because it is not.

Wrong layout on the PCB, but it shows you how it is done.

Had to turn the part around.
Here are two options of connecting it, with the first one you need to connect the gate by a trace that you need to add to connect the gate pad to a signal trace.

The second one allows to put the mosfet more inside the PCBā€™s center and does not need any new traces. Problem is, it may short signal trace and output trace if it manages to solder on the trace cut edge. It did not for me, although I used extra new traces for source and drain because I had cut there before and wanted to make it more solidly routed. I doubt it would solder there especially when not putting any paste near it but one never knows and has to check before plugging the driver anywhere.

And the result:

Works with an XM-L U3 fine but it pushes 3A soon so a resistor was used for testing the higher currents, 0.47ohm, 5W only so I have to watch not to burn it.
The XM-L U3 was hitting 3A at 3.3V or 3.4V hence I had to switch to the resistor.

Powered from my PSU although the PSU screams a little with the load, dunno why, probably because itā€™s lines are unbalanced and the load is PWM.
Canā€™t measure what it gives as voltage under load so itā€™s an idle voltage, 5V is loaded and should be stable, 3.3V line shows 3.4V but I guess it drops to 3.3V once itā€™s loaded.

nlite firmware, 18kHz PWM, 5ā€“33ā€“100% modes.

Load
0.47ohm (5W ceramic under a fan, poor thing even smelled once)

Test #1
U: 3.3V
L: 0.3A
M: 2.1A
H: 5.8A

Calculated total resistance 3.3/5.8 = 0.57ohm, means 0.1ohm on all connections and the mosfet combined if resistor really has 0.47ohm.

Test #2
U: 5V
L: 0.4A
M: 2.7A
H: 7.9A

Calculated total resistance 5/7.9 = 0.63ohm, means 0.16ohm on all connections and the mosfet combined.

Soldered connections apart from the PSU connection and I hold two wires on/off as a switch.
Can measure up to 20A, indirect, ACS712, 0.1A resolution on my meter.

Cables on the driver are maybe 4ā€, probably 0.5mm^2.

It should be doing more, but with all the resistances that add up on the route it does the above.

PSU should give 3.3V/28A and 5V/30A, hopefully it does under load.

The driver is dead cold, mosfet especially.
Even pushing it at the 8A I did not notice the mosfet getting any warm. Only a smell and a hot resistor J)

At 5V, 6mohm, it really doesnā€™t give a damn about 0.384W being dissipated on it. Itā€™s rated 3.1-4.8W depending on temperature. At lower voltages it goes to 10mohm at 3.3V and 20mohm at 3.0V (datasheet). Even if it would give 15A at 3.0V with 20mohm, it dissipates 4.5W. At 3.3V, 10mohm, 20A with 4W on the mosfet. 4.5V, 7mohm, 25A, 4.375W. Itā€™s rated around 20A.

I think the traces or flashlight would caught on fire sooner than the mosfet would die.

IMPORTANT:
When I drive it on 5V PSU and have it in low mode, it switches after a short while automatically into medium mode. I think this is because the capacitor on the ATtiny13A does not filter the voltage enough. Itā€™s the only mode and combination when it does that, consistently. Maybe it interferes with the PSU, dunno.

I also wasnā€™t able to reprogram the ATtiny when the capacitor was missing, dunno why it needs it, but without it it wonā€™t reprogramā€¦ it acts as if it does not see the ATtiny.
With my DIY clip it can be reprogrammed even in this position when the mosfet is closer to the MCU. And should be fine with other clips too unless you have some crazy beefy clip, then just file the plastic off the clip :stuck_out_tongue:

I will try moon mode now and try running it from an 26650, protected, may even try the unprotected Samsung 18650 beast, just donā€™t want to accidentally short it.

Might add 4-5 AMC7135s to make a medium mode without PWM and avoid the crazy spikes on low mode. Thatā€™s always an option.

48

Have you seen the new SRK clone driver?

It does over 8A from a single 20R into 3 parallel XML2s. I haven't checked it with a single cell & single LED, but it should be way up there still. Might be neat to try one on a East-092 PCB and see what happens.

49

lol these Chinese ā€œdriversā€.

Why do they always limit the current with resistors in series? Itā€™s the cheapest trick ever, lets limit current with more resistance and waste the power as heat.
No idea what mosfet that is, no datasheet found.
The power line has unnecessary 25mohm on the driver to limit the current. These resistors usually get bloody hot. Lets say it does 8A, drop on those resistors then is 0.2V, and they waste 1.6W as heat. Nice :wink:

Removing those will bump it into less resistive direct drive. That obviously will bring the amps and total power up as well.

I only have 2 soldered free XM-Ls thatā€™s why I took the resistor to simulate higher loads and see if it holds up well. It does as expected.

50

That driver's an easy fix:

Set up like that it pulls more current than any of my meters can measure.

51

Yup. 3 XM-Ls direct drive? From 3P 18650?
I only hope it has an electronic switch, it looks like it does.

In the higher amperage setups a little resistance can do big loses.

We still miss some decent 2S/3S drivers though, these 1S drivers are easy to make.
Making an efficient switching buck driver is not so much. Nor a boost driver. At least in the 2A+ of output range.

52

Test #3
TF 26650 4300mAh, protected

U: 4.14V - 4.11V
N: 0.0A
L: 0.5A
M: 2.8A
H: 7.6A+*

Protection trips on high.
And the moon mode is either entered only rarely or quickly jumps to low as I get a reading of 0.5A, then medium 2.8A and then high* very shortly shows on my DMM a jump to 7A+ and it immediately trips the protection.

Guess I shall charge up the Samsung INR18650-20R, unprotected of course and see what it pulls on the 0.47ohm.

I have to run a fan on the resistor, it heats up quickly being rated only for 5W.

This is even more than my PSU at 5V was giving me, guess the connections to the PSU and all the cabling adds resistance that is noticeable at these 5A+ loads. Or itā€™s the PWM load that interferes with the PSUā€™s capabilities.

Have the 26650 in a cradle and cables pressed from both sides to it.

Test #4
Samsung INR18650-20R 2000mAh, unprotected

U: 4.20V ā€“ 4.13V
N: 0.0A-0.2A?
L: 0.5A
M: 3.1A
H: 8.1A

Found a mode when it gives me 0.2A sometimes. Trying to get it the same as I have my nlite in a flashlight, this classic memory is a piece of ā€¦
Ok fixed, still it seems to me that it likes too much to switch to the next mode instead of the first one that is moon. Dunno why, probably the spikes or me switching power on/off with two wires is what causes it. Must be the sparks I hear from the cables when connecting and disconnecting. Could be fixable by enabling brownout and longer start up time.

The battery dips 0.3V under those 8A.
0.1V under 3.1A it seems. And 0V under moon, 0.02V at 0.5A.

3.85V, 8.1A, gives 0.4753ohm, 0.47ohm load, means only 0.0053ohm resistance of all connections O.O
Thatā€™s about the resistance of the mosfet and maybe not even that. Damn close, damn low.

Yes that was 31.185W right into that 5W rated resistor. Did I mention it smelled again? 0:)

53

nice work!

54

k4212:

nice one, I want to find one in this size with the lower vgs and rds on possible

I will use many mosfet in paralel for get lower rds on


55

That quite sucks Rdson to Vgs graph.

Plus putting many in parallel will increase already high capacitance of the input.
Plus these big mosfets have high input capacitance. Are you driving them only from the MCU or with an extra smaller transistor/fet to drive the gates of the bigger ones?

Plus in this size you only need one mosfet. Depending on Vgs these things can drive crazy amounts of current, tens to hundreds of amps.

Browse the catalogs of the shops available to you and see what they have. Filter by the parameters you desire.

The low Vgs ones are hard to find, since many mosfets are really made to work from 4 to 4.5V up.

56

yes but The capacitance is irrelevant because in the high mode the voltage VGS is continuous, is not pulsing

many mosfet in paralel will have lower rds than one

In this flashlight with only a mosfet the mosfet are heated , but with 4 mosfets the mosfets stay cold



57

If you only want a single direct drive mode, sure.

What current and what voltages?
You shouldnā€™t really notice using single or many mosfets, unless you pick some higher Rdson one.

If switching is not an issue and you have 2 cell voltage, hey you can go to those powerful ones.

Since you want low Vgs I suppose itā€™s a single cell? Then youā€™re screwed like the rest of us :wink:
Look at many and see what fits your use.

But looking at your schema you have 2 cell so use that 2 cell voltage to the mosfet gates.

Anyway this is one of the things used for DC motors, under high loads with high spikes too.

IRLS3034-7PBBF
Used on 2 cell and 3 cell.

But it is not turning on and off fast, 1us for a cycle. Has capacitance of 11nF and Qg of 120-180nC.

On the other hand it has Rdson of below 2mOhm at 4.5V Vgs.
Unfortunately does not list Rdson vs Vgs graph, itā€™s only noted that it is low at 4.5V.

They do switch it, although I do not know how fast, to drive a DC motor.
You can imagine the noise and rubbish this creates :bigsmile:

It is not big, itā€™s a D2PAK. Itā€™s from a tiny motor driver. Probably similar in size to those big mosfets you have on pictures.

Should be safe to 100-200A continuous at 4.5V Vgs. Enough? :wink:

Not the cheapest though, depending on where and how many you order, $4-$7 on places like digikey I see.

2.5V catalog
4.5V catalog

The IRLS3034-7PPBF is under 2.5V Vgs threshold.

Just be aware that it has high input capacitance and is not as fast as what most are used to in drivers and run them at 18kHz.

HELL

here you have even better one they use now

irf6718l2pbf

Not sure of cost but specs are even better. Much better. But itā€™s surface mounted and you might not like the package. They use them dual, as in 2 at the same time in parallel. Why, I donā€™t know, one is enough :smiley:

Do you need these for a flashlight? Most likely not.
For some big ass search light? I guess you do.

58

Sure you always notice the Rdson in high current applicationsā€¦so a simple workaround is the paralleling of some FETsā€¦

On 10A 50mohm difference cause 0.5V voltage drop and voltage is very important in these direct drive drivers.
Not to mention that everything else has to be zero resistance modded too.
ā€”ā€”
As often mentioned in this thread irl3803 is a very common choice for a nfet in a to220 housingā€¦please donā€™t recommend FETs which you have not tested yet.

59

Yeah but decent mosfets have Rdson 10mohm or lower and the power mosfets are at 3mOhm or lower.

The two power mosfets have 0.5-1.5mOhm.
Sure it helps to use more in parallel but it may be difficult to drive them if you want to switch them on/off by PWM.

I would skip mosfets that have 20mOhm and higher Rdson, just not worth the money and effort for applications with 5A and more. Thatā€™s an instant 0.1V drop just on the mosfet. Thatā€™s too much, 0.5W too.

The IRLS3034-7PBBF and irf6718l2pbf are used for DC motor driving, by a PIC controller. I could ask how high frequency they use to drive them if somebody is serious to use them, or I can forward you to the page/forum.

60

So far so good, SiR424DP with nlite firmware 18kHz, moon, low 5, medium 33, high (direct drive), work flawless in an assembled light, 3x Nichia + a protected Sanyo UR18650FM, not much charged, first tests, playing it safe. Plus have magnets to extend the battery, will be shortening later.

Samsung INR18650-20R unprotected, charged 4.2V:

N: 0.1A
L: 0.3A
M: 2.0A+
H: 6.5A+

But it does depend on the resistances caused by me connecting the wires from the ampere-meter. Can be 6.2A and if I press harder it goes 6.5A.

This is 3x parallel Nichia 219A from IS, on copper noctigon and copper moded pill.
Yes over 2A in direct drive for each of the Nichias on copper.

Seems like there is no need to use 7135s for any lower modes. Apart from somebody wanting a super low moon mode.