T2 laser comes on when going to laser control. SOLVED!!

[Koskee]

Before you "order a 1k resistor" I would suggest ordering a pack of them, many different values. For the price you'll end up paying for a single + shipping,  you can get a handful of all different kinds that (assuming you will be doing something with electronics down the road) will come in handy at times you never would have expected. A few dollars will score you anywhere up to 50 different values x 10 of each. There's smaller packs as well.  Check eBay or whatever your site of preference may be. These are always good to have on hand, and are plenty cheap enough to do so. Then the value doesn't really matter until you receive them & then you won't order the wrong one!

Edit: I tried a 10K, and the effect was the opposite.. The laser still works, however, it also still turns on when going into the control interface, so now I will try values between 1k and 10k until I find something suitable.

I tried to use the scope on it, didn't really get very far with it other than I had what appeared to be a PWM signal that kind of looked like --> I==I==I== (not really sure how I can use that to find the appropriate value, but the signal was in the 2us range if that means anything? Like I said this thing is analog as fk, and hasn't been calibrated since the early 90s lol)

[Stonemull]

I just turned my damn laser on full power while not wearing goggles dammit.

Turned off the nano while motor switch was still on.

Added the 1k resistor but put it on the laser itself as I figure it is the laser that should be off with a floating signal.
If you have a bunch of SMD resistors and a small iron tip I suggest this is the correct location, soldered between the pwm and ground pins on the back of the laser board, no screws need to be removed as it is an accessible spot with the driver board still attached to the laser.

You might have to zoom in to see it. Also it does not totally kill the laser when floating but it is not full power any longer, just slightly brighter than the 'safe' mode button, at least it is not likely to cause damage any longer.

[Koskee]

^ Pictures a little dark, but i see it! Only problem with it done this way is that it becomes no longer a "universal fix" that can be recommended to anyone with a mana board.. For example, I couldn't do this because I have a different laser module.

 Also I can report that with my mana se board and the 3.5w TTL laser (as discussed before in this thread) that these are my results so far:

1K - laser became completely unresponsive (actual value ~985ohm)
10K - no effect, laser still comes on (actual value ~9.89Kohm)
4.7K - no effect, laser still comes on (actual value ~4.66K)
(slowly chipping away at it since it's not super urgent and it would be super tedious to do it all in one go.. Will report findings once I have them)

[a_kent]

That's the way it should work, Stonemull! Nice job with the SMD part.

It would also be interesting Koskee, to know why the 1k stops the 3.5 watt laser. It should not. It's just a digital signal going to the laser controller. A scope on the PWM would be interesting to see.

Kent

[Stonemull]

I can't see why 1k would kill it either, I am pretty sure the nano pin goes straight to the laser terminals with no series resistor, a nano should be capable of 20mA for a single pin, so driving down to around 200 ohms should be fine.
odd ..

[Koskee]

Maybe a loose fitting connector, parasitic resistance &  capacitance on the pcb traces, internal pullup, or the fact that the single pin is split into 3 separate servo, laser and motor connections (including MOSFET circuit) could add up to enough that he pin wasn't able to drive to the minimum 2.7V to properly propogate the ttl/pwm signal down the line?
Just guessing though.

It appears that the value is going to need to be between 1k and 4k7 anyway,  based on preliminaries, so it's not very far off from the suggested value if anything? Not really sure.

Could also be affected by the kind of wire I used between mana + ttl, since I didn't get one with either purchase, I had to make one.

[Stonemull]

Loose fitting connector and perhaps a pull up on the laser would be the only valid concerns of that bunch.
The frequency is only 1 or 7.8khz depending on grbl version, mosfet gate is going to appears as a very small capacitance, the board does not even have a ground plane and paralelling a few connectors is not going to make capacitance any sort of issue.
In reality anything from 1k to 100k should do the job so I suspect the laser module has some odd input schematic to cause the weird response.
I would attempt to trace it out however it needs desoldering to remove and the interface chip has had its numbers sanded off.

[Koskee]

Tried a couple more values tonite:
2K2 - 2.168k actual - no effect
1k5 - 1.461k actual - this value worked for me. Laser still functions, and does not turn on when it shouldn't.
So it appears that the prescribed value of 1k was not far off the mark for me, and the actual value of the initial resistor I used was lower than 1k (i think i metered it at ~968ohm but i didn't write it down, so going by memory). This is interesting because the same mod with a 2k2 did not yield results, and (barely) lower than 1k in the initial trial ended up modifying the signal so that it was not recognized. This seemingly gives a pretty narrow window for what values will work on my system. Something like 1K < R < 2K? Not sure why it would be quite so lucky, but it works now, so I'm satisfied.

[Zax]

It shouldn't be that sensitive to resistance but glad you worked it out, 1.5k is very reasonable for a pull down.

[bernd.dk]

1 k ohm / 0.25 W ---- the perfect solution for my system. It cost me about 10 cents and took 10 minutes.

[kered]

For testing and finding the exact resister could i just push the legs of the resistor into the required pins on the back of the cable? would save a lot of soldering and desoldering.

cheers
Derek

[bernd.dk]

Maybe with some hot glue ?, but I'm not sure you get electrical contact in this way. Just try and solder the small (0.25W/1KOhm) resistor, it's hard to destroy the print and there are no components on the opposite side.

[Zax]

It will work just fine pushed in the connector, in fact I ran one of my lasers like that for a month before finally soldering it on the laser module input.

[kered]

Thanks Zax, it will just till i find the right one then I'll solder it, a lot easier and faster to just plug & test, change , plug & test etc. once found then solder it.
cheers
Derek

[minora72]

Resistor added. VERY SIMPLE procedure... no laser discharge when switching on/off from T2laser.  Now I wish the trace frame could turn on and off through the software...

Always left wanting more!