Nanjg AK-47A Slow Blink?

Flashlight Modding and DIY Parts
1

I’ve done something a bit unorthodox in using a 4.5V wall wart to power a Cree XP-G2 via a Nanjg AK-47A.

I was running the heatsinked driver and LED for a several hours when I noticed the LED started a slow blink. The blink looks identical to the low voltage blink but since it was being powered by a wall wart, low voltage seems quite impossible.

The particular driver I was testing was completely stock and I was running a multimeter in line testing the current. Current had held steady at 1.0A+ for quite a few hours before the blink suddenly began.

Tried a search but didn’t come across anything.

Any ideas?

Thanks in advance.

2

Did you confirm the wall wart didn’t fail? Is the wart rated for 1 amp continuous output?

3

I’m very confident in the wall wart. Been using them for quite awhile without issue.

Forgot to include that the power supply is rated at 4.5v @ 2.0A continuous draw.

4

IN that case, you had a device failure on the driver. You can test the MP sub-function by connecting positive directly to the right pin of one of the 7135’s. You might also put a meter across the divider network (resistor pair) and see if this failed for some reason. The diode is still functioning because you do still have a signal being sent tot he 7135’s. Therefore, the only remaining function that can cause this is two resistors or an internal MP failure.

5

Forgive the ignorance but what is the MP sub-function?

Is this a common problem with theses boards?

Also left out that a brief click of the switch returned it to it’s normal operation where it’s been running for nearly a day.

6

MP sub-function just refers to the operation of the micro processor.

Obviously there was an interrupt in the power source and this locks the MP into low power mode. Resetting the power will resolve this. I’m going to suggest you experienced a brown-out and the wall wart dropped below 2.8V and it locked into the alarm state.

I use NANJG drivers exclusively and never had this happened.

7

I appreciate your input here and have a possibly related question. Perhaps it deserves a different thread but I thought I’d try here first.

If these circuits are not properly heatsinked, I have found that they will step down the power. Does anyone know if this is the result of the way they’re programmed (IE, built in protection to step down when overheating) or whether this is the result of the individual AMC7135’s shutting down because they physically cannot operate at the higher temps?

Thanks.

8

The AMC7135’s have a built-in fold back to about 250ma when they get too hot.

9

A weak connection or partial click can sometimes cause this. The attiny chip misinterprets this as a low power condition and goes into low voltage warning mode. Reset fixes this.

10

Thanks all for the input.

NightSpy - I ended up finding your post on “thermal fold back” and found it helpful.

Any idea if prolonged operation under thermal fold back would damage the circuit or it’s components?

11

My experiment showed that the thermal issue dissipated at this fold-back current so I do not know if it continues to step down or not.
There is some built-in hysteresis because it would take several seconds for it to go back into fold-back when the output is restored.

12

Just wanted to check and see if there was anything theoretically damaging in operating the circuits under thermal fold-back for a prolonged period.

FWIW, I’ve operated these circuits while under thermal fold-back for many days, if not weeks at a time and have not noticed in permanent effects. Since I don’t know anything about circuits, or even how they’re programmed to act, this experiment was my only point of reference.

13

Me too. I was just pleasantly surprised this happened. Never had a flashlight do this but most of my lights are within design specs, not overdriven.