Smokin' !!

[shobley]

What does it mean when smoke comes out of your galvo, and then from that point on the amp runs really hot, and the galvo "shakes" - ie a dot comes out as a short line?

This happened to my laser harp yesterday . I've checked over the input signals and they're all OK, the PSU is functioning normally too.

Exactly 1 year of service, almost to the day...

[Diachi]

Doesn't look good , smoke coming out of any electronic component is usually not good ! what kinda noise did it make when it went ?

[allthatwhichis]

My condolences... magic smoke = dead galvo... It was blue smoke wasn't it?

[shobley]

It kind of buzzes now, and the amp gets way hotter than it used to.

The smoke was more like a purple haze...

I would love to know what went wrong...

Oh well, from the ashes shall rise Laser Harp III ...

[Carl B]

Hi Sholby

That is bad news to hear as that harp is awesome, much better than mine that uses a diffraction grating for the beams and over head sensors. You do have a spare galvo from the ScanPro set you bought?

I'm looking to move on to a frame-less harp using a galvo but my limited knowledge of electronics and zero experience with code programing this is going to be one big challenge. Rob Stanwax as offered to help me with the electronics were he can and his help will be most gratefully appreciated.

I have a set of ScanPro 20's set aside for this job. Just hope your galvo is a one off and is not going to plage all harps that use these scanners.

hope you get it sorted. Have you had chance to use the harp in a live performance?

Carl

Ps JM Jarre is starting a new arena tour in Europe performing his greatest hits. I think his harp is going to appear in the show. Keep your eyes and ears open as this may become a World arena tour.

[shobley]

The X axis was never that good - it's in better shape than the Y is now though. I currently have this installed and it's still a bit shaky.

I don't know if I broke the X axis a while ago - it's been while since I looked at it.

I'll be rebuilding the harp later in the year, making it much more robust than my prototype. If all goes to plan, I'll be posting a step by step build diary.

I've got a new axis on it's way, I'll be testing this out with my "proper" DAC setup first just to make sure that nothing is wrong.

[carmangary]

Smoke out of the galvo means too much current went through it and started melting the insulation off of the windings. The amp gets hot for the same reason, too much current.

The obvious question is, what caused the excessive current? It could have been a bad position sensor or feedback circuitry that caused the amp to try to incorrectly compensate. That would be my first guess.

So, don't just replace the galvo because it might have been the scanner amp that caused its destruction.

[QUAZAR]

You need to catch the smoke and put it back into the galvo.

Or put the galvo in the bin. Whatever is easiest.

[The_Doctor]

My guess is the galvo had to repeatedly aim at the same spots, and got the galvo equivalent of RSI. Likely flats in bearings, increased resistance, exponential rise in stress at last moments resulting in increased resistance and overheating, and noise caused by roughness in bearings which also makes the spots ill-defined.

What might preserve it in future is to add a DC offset tweak, and rotate the galvo on its mount a few degrees once a week or every hundred hours of use, so that you get teh same aim points but don't flatten exactly the same bit of bearing each week.