Nanjg AK-47 driver low voltage blink

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Bra Ljus
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Nanjg AK-47 driver low voltage blink

When powering from a PV solar panel with battery charger set-up, there is a time when the voltage from the PV solar panel is no longer sufficient and the battery takes over (as it should). Eventually, at the end of the night, the battery is depleted.

Before, though, the driver already enters the low voltage warning blinking mode (as it should according to factory firmware description) and when in the morning the sun comes up again, also charging the battery, the driver remains in the blinking mode, although PV solar panel and battery voltage are soon fully restored. The driver is “stuck” in low voltage warning mode.

I need unattended operation of this set-up over many weeks.

Is there a way to simply disable the (otherwise useful) low voltage warning blink?

Tack!

moderator007
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You can use this driver which is basically the same driver but without the mcu and modes.
https://www.fasttech.com/product/1127404-3v5v-4-amc7135-led-flashlight-d...
They offer different current outputs but the out put is simple adjusted by the number of amc7135’s that’s installed.
If it has 4 amc7135’s it’s 1400ma (350ma each amc7135) remove one for 1050ma.
.
I think you can connect Vdd directly to source positive and it will bypass the mcu and LVP. I would remove the mcu, scratch off the coating on the green trace that runs right by the center led positive pad and solder the trace to the led positive pad, that should do it.

Bra Ljus
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Thanks, I need the 1050mA version https://www.fasttech.com/products/1612/10001751/1127406 but that one then has no three-step-dimming settings…

moderator007
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If your keeping the modes, then the only way I know would be to reprogram the mcu an take out the LVP code.
Or rewrite the code to where it isn’t looped once LVP is run.
http://budgetlightforum.com/node/36216

Bra Ljus
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Thanks, well, that seems well beyond my capabilities; I had hoped there would be a version simply without that low voltage blinking.

In that case, I will buy the mode-less version and select a less powerful LED, so my battery will not drain faster from the then single-high-mode.

moderator007
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The number of amc7135’s that are on the board determine the out put. Each amc7135 gives you 350ma out to the led. 1 amc7135’s gives you 350 ma, 2 700 ma and 3 1050 ma. Simply removing them or adding them changes the out put to your liking. Picking the most efficient led at low current would give the most lumens per watt.
The way the amc7135’s work you will get exactly 350, 700, 1050 ma out no matter which led you choose as long as the battery voltage is above the vf of the led.

Lightbringer
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You’re using a Li-ion cell in a PV setup? Or LFP? Or series NiMH/NiCd/etc.?

(There’s a reason I’m asking…)

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Bra Ljus
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It’s that set-up:

1. Cree® XLamp® XP-L LEDXPLAWT-00-0000-000UU30E7 – 3000K, 320lm, CRI 90, 1050mA, 2.95V & matching MCPCB & matching Fischer fcool heat-sink
2. OLIMEX Li-Ion rechargeable battery – 1s, 3.7V, 3000mAh
3. Adafruit USB / DC / Solar Lithium Ion/Polymer charger – v2
4. Nanjg AK-47A 7135*3 1050mA LED driver
5. ON Semiconductor NDP6020P‎ P channel MOSFET + pull-up and gate resistor
6. Voltaic 6W PV solar panel

So I need to get rid of the blink, useful for flashlights, but not for unattended operation over weeks – hence I will have to buy the generic “no modes” 1050mA version that moderator007 mentioned above.

Lightbringer
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Hmmm. Was gonna say, if you’d be willing to ditch the Li-ion cell and switch to NiMH or LFP cells, you can get an 800mA boost driver. They’ll deliver that much fine with 3V, about 500mA with 1.5V. Don’t think they have LV blinkies at all, just cut out when the source gets too weak to supply, well, anything.

LFP cells are pretty much flat from just-off-the-charger to crapping-out, and would supply at least 800mA to the LED. That 20% difference in current wouldn’t translate to very much visual difference in brightness.

Nb: 1A from a 3000mAH cell is only 3hrs runtime from fully topped-off to pretty much dead-and-blinking.

Also thinking maybe a few extra cells might not ever get fully topped-off (increasing longevity), but would give a longer runtime. Getting to 90% or so is pretty quick, but topping off to 100% takes lots more time as the cell slow-fills. So who cares if you only get to 90% from the solar cell, but have longer runtime overall?

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Bra Ljus
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Yeah, I had that on the other thread, the three balcony, terrace and garden lanterns.

The above set-up lasts 3.5 hours on full and 7 hours on half (Nanjg AK-47 with the three default modes), and half brightness until the sun comes up to charge the battery is ok for the purpose; the thing has to be very light and small.

Lightbringer
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Wellp, you can try a “dumb” 1050 and if need be just take a razor to a trace and turn it into a 700 for more runtime. Or have a switch (vs using a “smart” driver).

The center pin of 7135s is the chip-enable, so make/break turns the 3rd chip on/off.

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Bra Ljus
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Now that’s a good idea. Take one of the 7135ers out for a good “perma-dim” feature ; )

Bra Ljus
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Lightbringer, would it not then be possible to make a bare-bones no-modes 3*7135 driver “dimmable” by attaching a switch that will enable and disable the third 7135 IC?

Thanks!

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Yeh, that’s what I meant above. An external switch could turn on/off the 3rd chip, to switch from 700mA/1050mA as you’d want.

Or electrically switch it (eg, photocell dimming it on a brightly moonlit night, etc.).

Go crazy…

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Bra Ljus
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Currently, a P channel MOSFET switches the LED driver on when no sunlight is present, and off when sunlight is present, so that works really well.

Do you happen to have a circuit diagram between which contacts a switch would need to be wired to take the third 7135 out?

It’s clear why the driver with factory modes always comes on in blinking mode – as the sun goes down, the MOSFET slowly begins to enable source to drain conductance, and, despite the battery being charged fully at 4.2V, the initial voltage passed through is minimal, hence the low voltage protection in the driver thinks “Uh, low battery, better start blinkin’…” and then remains in that state.

Thanks!

Lightbringer
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Not really. You can either take a razor to a trace, or desolder-and-lift, the middle pin of whichever one’s most convenient.

The switch would just bridge or unbridge where you broke contact (slicing or desoldering).

Picture snipping a wire and sticking a switch inline instead.

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Bra Ljus
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Ok, right, the middle pin trace it is then, thanks for reminding me.

This autonomous PV solar light thing is fun, even at @357 lumens for 3.5 hours, with 3000K and Ra 93.

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If you follow the traces on each 7135, the tabs will be grounded (usually around the periphery), the middles will go to a µC if one exists, else pulled high to the battery voltage through a diode, and the other end will be in common and go to the negative end of the LED.

Only thing to be careful of, is that if the enables are daisy-chained, and if you cut a trace, you might be disabling 2 of the 3, or possibly (‘though unlikely) all 3 of the 3. So maybe it’s worth the effort to just desolder’n‘lift the enable of 1 chip only, to be sure.

Don’t desolder the whole chip, just the middle pin. “One pin, Vasiliy. One pin only, please.”

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kikkoman
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If you don’t need the LVP blink at all, you can modify the resistor divider (or just desoldering the lower 4k7 one probably works too.)
If space permits it, you could wire in a switch so you can turn the LVP on/off.

moderator007
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kikkoman wrote:
If you don’t need the LVP blink at all, you can modify the resistor divider (or just desoldering the lower 4k7 one probably works too.)
If space permits it, you could wire in a switch so you can turn the LVP on/off.

I didn’t even think of that, that be the best way and you could use the driver you already have.
@lightbringer Putting the switch on the middle pin would mean the current runs thru the switch and wires if wired in. Putting the switch on the vdd pin would mean the 7135 is either turned on or off with voltage and the current runs thru ground and out.
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Wait, what? The middle pin’s not the enable pin (eg, goes to the µC)?

Okay, whichever pin’s the enable, that’s the one you want to desolder’n‘lift. LOL

Not ground, not the one that goes to the LED, the leftover one.

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Bra Ljus
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If you three don’t mind, could you draw into the below image of the driver I currently have

1. Where I would have to cut a trace to permanently disable the 3rd 7135
2. Or where I would have to wire in a switch to not permanently disable the 3rd 7135
3. And, most importantly, which “resistor divider” I could modify to disable the blinking low voltage warning

Thanks a lot in advance!

Otherwise, I could buy that bare-bones 7135*2 version from FastTech, but that’ll take three weeks : (

kikkoman
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Your pic doesn’t work so I assume it looks like this.

If you want to have a switch for LVP too, remove the marked resistor , solder it in series with a switch and wire this to the pads where the resistor was. (Or, more simply, between the outer ring and pin 7 of the µC)
For permanently disabling LVP, just remove the resistor.

Bra Ljus
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Perfect, thank you so much!