Weird.

[mfo]

Ok. I was playing with my LPC-815 LOC yesterday. I'm driving it with a Rkcstr @ 400mA. I'm using the 3405 host by jayrob. This host has a big heat sink but I limit my duty cycle to a minute or two tops. Anyhow I was in a dark room just pointing it at my ceiling waving it around. It was focused to infinity. After about a minute I noticed it started to pulse! At first I thought this was some kind of illusion because I was also messing with my GLP 473 that I just received from Glenn's GB. So my red will pulse after having it on for a minute or so. I'm guessing heat could be the cause? I'm stumped on this one.

 

[nikokapo]

Ok. I was playing with my LPC-815 LOC yesterday. I'm driving it with a Rkcstr @ 400mA. I'm using the 3405 host by jayrob. This host has a big heat sink but I limit my duty cycle to a minute or two tops. Anyhow I was in a dark room just pointing it at my ceiling waving it around. It was focused to infinity. After about a minute I noticed it started to pulse! At first I thought this was some kind of illusion because I was also messing with my GLP 473 that I just received from Glenn's GB. So my red will pulse after having it on for a minute or so. I'm guessing heat could be the cause? I'm stumped on this one.

This exact same thing happens with some Romisen L-C030 I got from DX, but sadly I can't extrapolate the experience because yours is a semiconductor and mine are DPSS. My first guess is heat, somehow it makes a component "slow down". It's one of the mysteries I've never solved.

The weird thing is that the pulsing happens when the laser is turned on from a cold start; I mean, it doesn't start to pulse after some minutes, it starts pulsed and then it settles.

 

[mfo]

This exact same thing happens with some Romisen L-C030 I got from DX, but sadly I can't extrapolate the experience because yours is a semiconductor and mine are DPSS. My first guess is heat, somehow it makes a component "slow down". It's one of the mysteries I've never solved.

The weird thing is that the pulsing happens when the laser is turned on from a cold start; I mean, it doesn't start to pulse after some minutes, it starts pulsed and then it settles.

Very strange. I'm guessing the driver is getting too warm? The driver is housed inside of the aixiz module. Strangeness!

 

[brtaman]

Very strange. I'm guessing the driver is getting too warm? The driver is housed inside of the aixiz module. Strangeness!

Did you check the battery voltage?

I would say that their voltage dropped to a point where the regulator fell out of regulation, which caused the strange pulsing. It is the only "active" thing within the laser.

 

[mfo]

Did you check the battery voltage?

I would say that their voltage dropped to a point where the regulator fell out of regulation and started pulsing. It is the only "active" thing within the laser.

Didn't do that since they were just recently charged. Usually when the batteries die however the laser just starts getting noticeably dimmer.

 

[nikokapo]

Did you check the battery voltage?

I would say that their voltage dropped to a point where the regulator fell out of regulation, which caused the strange pulsing. It is the only "active" thing within the laser.

Mine does not choose between batteries, it does the same will all of them. Charged, partially charged, etc.

 

[HIMNL9]

LM based ICs have a thermal protection, but usually don't pulse ..... it shut down the IC when junction reach 125C, and re-enable it when the temp go down til 65C ..... too large hysteresis for cause pulsations .....

 

[mfo]

LM based ICs have a thermal protection, but usually don't pulse ..... it shut down the IC when junction reach 125C, and re-enable it when the temp go down til 65C ..... too large hysteresis for cause pulsations .....

What is LM and IC?

 

[HIMNL9]

Sorry ..... LM = LM117 / LM family of ICs ..... IC = Integrated Circuit (regulator, in this case) ..... the "rkcstr" drivers uses them.

 

[mfo]

Sorry ..... LM = LM117 / LM family of ICs ..... IC = Integrated Circuit (regulator, in this case) ..... the "rkcstr" drivers uses them.

So basically my driver is getting too hot?

 

[HIMNL9]

Uhm, no, i doubt this ..... as i said, the hysteresis from the different temperatures is a bit too high for cause a quick pulse ..... can be the case if, as example, the pulses are seconds long, like 10 or 15 seconds on and off .....

BTW, do you use protected li-ion batteries ?

 

[mfo]

Uhm, no, i doubt this ..... as i said, the hysteresis from the different temperatures is a bit too high for cause a quick pulse ..... can be the case if, as example, the pulses are seconds long, like 10 or 15 seconds on and off .....

BTW, do you use protected li-ion batteries ?

I'm using two unprotected, one protected. The pulsing won't stop until I turn off the laser. If I turn the laser back on after a few seconds, it will begin to pulse again within seconds. Sounds like a heat issue to me...

 

[nikokapo]

Uhm, no, i doubt this ..... as i said, the hysteresis from the different temperatures is a bit too high for cause a quick pulse ..... can be the case if, as example, the pulses are seconds long, like 10 or 15 seconds on and off .....

BTW, do you use protected li-ion batteries ?

Same here, I thought about hysteresis but the difference should be FREAKING big for us to notice it pulsing. I am using Li-Ion batts (3,6-4,2v).

 

[brtaman]

LM based ICs have a thermal protection, but usually don't pulse ..... it shut down the IC when junction reach 125C, and re-enable it when the temp go down til 65C ..... too large hysteresis for cause pulsations .....

Also an option, my laser usually also just dimmed when the batteries went down, it is quite a strange symptom to get in a linear driver.

Perhaps the internal thermistor is damaged? Though I have not heard of that happening. I can think of no situation in which the temperature of the IC would be "jumping" enough to cause pulsation.

mfo: have you considered replacing the LM on the driver board? Have you tried using a different pair of batteries?

 

[HIMNL9]

There is another possibility, but is strange ..... i mean, you're using two unprotected and one protected cell ..... if the protected cell is at low charge limit (or if is defective or at the end of his life cycle), with the load of the laser it can go under the protection limit, and the protection circuit open the connection (same as turn off the laser), and there, with no load, the battery go up a bit, and the protection circuit close again the connection (and turn it on), and so on, cyclically ..... this can cause the pulsed work ..... usually it don't happens, but can be this the problem ..... you don't have another unprotected battery, or a different one, for try ?

 

[brtaman]

There is another possibility, but is strange ..... i mean, you're using two unprotected and one protected cell ..... if the protected cell is at low charge limit (or if is defective or at the end of his life cycle), with the load of the laser it can go under the protection limit, and the protection circuit open the connection (same as turn off the laser), and there, with no load, the battery go up a bit, and the protection circuit close again the connection (and turn it on), and so on, cyclically ..... this can cause the pulsed work ..... usually it don't happens, but can be this the problem ..... you don't have another unprotected battery, or a different one, for try ?

Yeah, that is what I was thinking as well, could also be a defective protection circuit or the scenario you are suggesting, that's why I asked if he tried a different pair of batteries.

Funny how even on the simplest circuit, the problems can be many. :yh: