7135 based driver on LiFePo battery? (=also IR light build thread, with measurements on Oslon Black 850nm led, mod finished now)

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djozz
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7135 based driver on LiFePo battery? (=also IR light build thread, with measurements on Oslon Black 850nm led, mod finished now)

I'm sure it is discussed before somewhere, but i can't find it.

I'm going to drive a IR led with a Vf between 1.5 and 2V (only 1A) with a AK47 driver on a LiFePo battery. The current chips will burn off quite a lot of excess voltage, I am not concerned about that, but does the controller chip actually run on only 2.5-3.6V ?

Edited by: djozz on 11/10/2013 - 18:40
Hikelite
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You mean the Attiny13A SSU microcontroller used on the Ak47?

djozz
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Hikelite wrote:

You mean the Attiny13A SSU microcontroller used on the Ak47?

that is the one, thanks, and I just found the datasheet: 1.8-5.5V, so I guess that answers my question. so the ak-47 should work, right?

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djozz wrote:

Hikelite wrote:

You mean the Attiny13A SSU microcontroller used on the Ak47?

that is the one, thanks, and I just found the datasheet: 1.8-5.5V, so I guess that answers my question. so the ak-47 should work, right?

Should work at such input voltage, but here's the firmware should have some sort of voltage warning at 2.9-3V.

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Hikelite wrote:

djozz wrote:

Hikelite wrote:

You mean the Attiny13A SSU microcontroller used on the Ak47?

that is the one, thanks, and I just found the datasheet: 1.8-5.5V, so I guess that answers my question. so the ak-47 should work, right?

Should work at such input voltage, but here's the firmware should have some sort of voltage warning at 2.9-3V.

ai, that could spoil it all. hmm, I will have a go at it, and if it does not work well enough (shut off early because 3V is reached, I may go for a bare 7135 driver without controller, or a boost driver, with a AA NiMh (eneloop).

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Or get a driver that has a different low voltage protection - from DrJones for example.

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Actually should flash to warn you of  the low voltage at around 3V.

I have not tried to see if the 7135 can output as lows as 1.5V-2.0V. I hooked one up the power supply (just a chip) and under 2.42V input will not work anymore with a XM-L1

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looked up some specs from the 7135 chip, minimal supply voltage is 2.7V, so that one will also drop out before the battery is drained.

I think I will try a AA boost driver then, any thought on if it (say the nanjg 110) will be happy boosting to 1.8V instead of 3+ V? I'd guess it will only be easier on the driver?

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Hikelite wrote:

Actually should flash to warn you of  the low voltage at around 3V.

I have not tried to see if the 7135 can output as lows as 1.5V-2.0V. I hooked one up the power supply (just a chip) and under 2.42V input will not work anymore with a XM-L1

thanks for checking, we were thinking the same Smile

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djozz wrote:

Hikelite wrote:

Actually should flash to warn you of  the low voltage at around 3V.

I have not tried to see if the 7135 can output as lows as 1.5V-2.0V. I hooked one up the power supply (just a chip) and under 2.42V input will not work anymore with a XM-L1

thanks for checking, we were thinking the same Smile

Yeah Smile I knew the spec is 2.7V so I wanted to check, but keep in mind this is only 1 chip tested and XM-L1 is emitting a firefly light at 2.42V.

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If the driver has low voltage protection, you could mod the battery voltage divider on the driver to change or disable the trip point.

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texaspyro wrote:
If the driver has low voltage protection, you could mod the battery voltage divider on the driver to change or disable the trip point.

I am not that into driver electronics, so I would not know which is the battery voltage divider on the AK47 and how to mod it. Enlighten me please Smile

I am also on another track: would a simple AA boost driver like is present stock on any cheap AA flashlight (like 1 mode sk68 clones) just do the trick: boost to whatever voltage is needed between 1.4 and 1.8V to get around 1000mA. Or will it supply too much voltage?. Or will it just not put out that low output voltage and stop working?

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There is almost no energy left in typical Lifepo4 below 2.8V,so you can use 7135 drivers without any modifications.

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The polarity protection diode consumes .6 volts.  So bypassing it will increase voltage to the MCU and, I guess, the PWM signal going out to the 7135's by that amount. 

Removing the 470 ohm resistor is supposed to eliminate the low voltage protection.

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I don’t know how much power output you need, but FWIW I ran a cheap chinese IR diode with just a NIMH @ 1.2-1.4V. The Vf was supposedly 1.8 as well, but I tried it for fun and it worked. More info in my post. The IR68.

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ImA4Wheelr wrote:

The polarity protection diode consumes .6 volts.  So bypassing it will increase voltage to the MCU and, I guess, the PWM signal going out to the 7135's by that amount. 

Removing the 470 ohm resistor is supposed to eliminate the low voltage protection.

Removing the diode also raises the low voltage trigger point - the MCU thinks the voltage is higher than what it's programmed for and calibrated for via the resistor.

edit: Wow, the way I put that is about as clear as mud. Low voltage function will not trip until the cell voltage is lower than it would be with the diode in place... er, that may not be much better. I think I need a nap! :Sp

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HBomb wrote:
I don't know how much power output you need, but FWIW I ran a cheap chinese IR diode with just a NIMH @ 1.2-1.4V. The Vf was supposedly 1.8 as well, but I tried it for fun and it worked. More info in my post. The "IR68":http://budgetlightforum.com/node/24706.[/quote]

I remember your thread well, I will probably put it in a sk68-clone host too . Well, I don't know either how much power I need because it is just for fun Smile  (apart from my daily edc-light I do not need any of my lights, it is all hobby), it is a Osram Oslon black 850nm led 600mW output (90deg. Output angle), it might put out a bit more light than your chinese led (so I will not point it at my son Wink ) . The aim is still is a suitable 1A driver, but if all else fails I will go for direct drive on AA's, thanks for the suggestion Smile

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Cool, good luck with the build djozz. Be sure to show off what you do with it Smile

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hmm, I did some testing on the led on copper tonight, I may at least want to go to 2A Evil

 

Here's the underside of the led, the solder pads footprint is smaller than an xpg but I reckoned it would fit a xpg Sinkpad. I just reflowed it:

And yes, it worked (50mA from led-tester), a very faint red glow in reality but my phone camera (even though it will have an IR-filter) picks up a bit more of the IR radiation:

The central heat sink pad of this led is unfortunately not electrically neutral (it is connected to led+) so it will be an extra challenge to fit this board into a flashlight while keeping a well enough heat path from led to the outside.

The test set-up, with the luxmeter clamped-in close to the top of the led to pick up enough radiation to measure anything at this insensitive wavelength. Ledboard on huge chunk of alu, directly connected to power supply.

2.8 A  Evil  :

And the data neatly put into a graph. The measurements are quick and dirty, as usual because of lack of time and motivation to do it well, but it all seems to make sense:

Of course the led had less than a minute (about 30 seconds) on the highest currents, but I reckon it should at least survive 2A for a while, even inside a flashlight Smile . The current really runs away with minime voltage rise, so I really want a good current regulated driver now.

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Whats your plan for this IR emitter btw?

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Member GMARSH made some custom Oslon PC boards for his high-powered TV-B-GONE flashlight… he might be able to supply one… http://budgetlightforum.com/node/16652?page=2#comment-447667

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Couple notes, based on my experience with the TV-B-Gone flashlights:

- The IR Oslon’s have two dies in series, so their forward voltage is double a typical IR LED. At 2.8A, the 940nm SFH4725S that I’m using has a ~3.7V forward voltage. This means a single LiFePO4 might not cut it.

- The center thermal pad of the Oslon is connected to the anode, so make sure the sinkpad is electrically isolated from the pill when you build the light. I’d suggest using thermal epoxy (arctic alumina, etc) instead of fujik, so there’s a hard insulating layer between sinkpad/pill. Measure with a DMM to ensure the pill/sinkpad are isolated when you’re done, otherwise you’ll short the cell when you turn the flashlight on.

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gmarsh wrote:
Couple notes, based on my experience with the TV-B-Gone flashlights: - The IR Oslon's have two dies in series, so their forward voltage is double a typical IR LED. At 2.8A, the 940nm SFH4725S that I'm using has a ~3.7V forward voltage. This means a single LiFePO4 might not cut it. - The center thermal pad of the Oslon is connected to the anode, so make sure the sinkpad is electrically isolated from the pill when you build the light. I'd suggest using thermal epoxy (arctic alumina, etc) instead of fujik, so there's a hard insulating layer between sinkpad/pill. Measure with a DMM to ensure the pill/sinkpad are isolated when you're done, otherwise you'll short the cell when you turn the flashlight on.

Thanks for the notes! The IR Oslon that I used is actually a different one, it has a 90 degrees beam angle (very round dome) instead of 150 degrees, and it apparently has its dies in parallel because the Vf is between 1.5 and 1.9V. It is part nr. SFH 4715S , I guess that your led is SFH 4725S. It makes my driver solution different from yours.

I will use arctic alumina adhesive to mount the led board Smile

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I should have got the in series version instead of the parallel version, it would have been much easier to drive. But I did not know there was one until now Sad

djozz
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I see in the thread that texaspyro linked that you put 2800mA through the (series) led. That would compare to 5.6A in my test, quite rough on the led I'd say Evil

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Ha, I didn’t know SFH4715 and SFH4715S were two different parts – S being the two-series-die version. If you’re using the non-S version, you’re fine with a LiFePO4 cell.

Both parts are rated at the same forward currents, interestingly (1A RMS, 5A pulse) – implying you can get twice the light out of the same package with the S version, even though the S version would presumably generate twice as much heat in the process.

Just caught texaspyro’s post – I mount my LEDs on a FR4 board, and I do have a couple of spares I could give up, but if your LED will be powered on continuously I’d say just stick with the sinkpad.

Oh; on a Nanjg 105C driver, remove R2 to disable low battery shutdown.

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Instead of isolating the sinkpad how about switching the build to be host positive?

Battery positive to the tail. Isolate the ground ring on the driver from the host, bring driver ground to a battery contact plate, connect driver positive to led.

Did you have a host in mind?

A reference image might help with some of the mod suggestions.


Counterfeit 18650s, 2,<a href=“http://

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I did not have enough time today for real flashlight modding, but I did test out a nanjg 105C on the Oslon, with succes Smile (after my output test and reading about gmarch's mods, I got greedy and wanted more than a ak47, but still thanks for the image Helios  <img src= "> )

I zapped out the R2 resistor, as suggested by gmarch (edit: and ImA4Wheelr) (thanks for that!). Then wired the driver to led and 14500 LiFePo battery, with the current measured at the led wire (the wire colours look funny: I accidentally swapped red and black at the led board):

I used the third star and got 0.13A on low, 0.85A on med, 2.6A on high (close enough for me). The driver gets hot fast, as expected, I need to pay attention to that in the mod.

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djozz wrote:

I zapped out the R2 resistor, as suggested by gmarch (thanks for that!).

You're welcome Smile

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ImA4Wheelr wrote:

djozz wrote:

I zapped out the R2 resistor, as suggested by gmarch (thanks for that!).

You're welcome Smile

Oh oh, apparantly I used a wrong word again Wink  , nothing personal.. Laughing (I lookedup "zap out" , it is nothing I intended to do to that poor resistor)

It sure is not easy for us non-native english speakers to just find correct words, and I am getting ever more careless about my language nowadays. (and I'm not even mentioning humour, we sound stiff and humourless in english)

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There is something wrong with “zap out”? I’m a native english speaker & it seems fine.
Perhaps I’m not cool enough to know.

Google brings up urbandictionary for “zap out” but often people add junk to urbandictionary.


Counterfeit 18650s, 2,<a href=“http://

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