My HeNe!

[ferd19]

Soo after a bit of looking around, I eventually found what I wanted and ordered an HeNe from the infamous Sam. After getting it, I put it together and placed it in a small model display case b/c it would probably be a bit neater there w/ much of the wiring hidden underneath. This is my first HeNe, so i'm very pleased w/ it, i love how it lights up!

 

[LtKernelPanic]

Nice. I just got the same kit from him today. After finding a 24v power brick I could use temporarily I've really happy with it. I wish I could have got a tube that shows more of the plasma though. On a related note how long do these tubes have to be off before the residual charge is dissipated? I know it won't hurt you but I'd be more afraid I'd drop it if I got an unexpected zap.

 

[ferd19]

Nice. I just got the same kit from him today. After finding a 24v power brick I could use temporarily I've really happy with it. I wish I could have got a tube that shows more of the plasma though. On a related note how long do these tubes have to be off before the residual charge is dissipated? I know it won't hurt you but I'd be more afraid I'd drop it if I got an unexpected zap.

Ya, i wish there would be more plasma shown, but it's still very neat regardless! I can't tell you how long it has to be off, but i'm not going to go around testing it every five minutes

 

[Tech_Junkie]

I know it won't hurt you but I'd be more afraid I'd drop it if I got an unexpected zap.

It wont KILL you, but it will hurt. Zap is an understatement, so be careful.

 

[Jimmymcjimthejim]

Getting shocked from the residual HeNe charge is like getting a static shock. Although it's not painful, it could trigger a reflex if you don't expect it. However, touching both the anode and cathode while the laser is powered is painful.

 

[LtKernelPanic]

Well after spending several hours over at Sam's FAQ (damned place is just as a big time suck as Wikipedia!) reading about HeNe's I didn't see any time frames mentioned but I did see mention of disconnecting the alden connectors and shorting the pins to discharge it.

TJ is right. It *will* hurt but not be lethal which is what I was trying to say but poorly worded. The average static shock you feel start somewhere around 10KV IIRC. Like I said before I'm not worried about pushing up daisies from getting zapped but rather being surprised when trying to pick it up and dropping it. A leather work glove should be enough to insulate you from any unexpected zaps if you need to handle a tube shortly after it's been on.

As for more plasma I'll be getting one of those $100 green HeNe tubes soon but I need to ask a question about them in another thread first.

 

[LtKernelPanic]

Well that's awesome. I went to straighten the wiring and make it look a little neater and one of the HV leads snapped about half an inch from the alden connector. It looks like the wire was mostly snipped though likely when the supply was removed from its original enclosure so you may want to check yours for any similar damage. I emailed Sam asking if it's something I can solder or if it'll need a new connector.

 

[Tech_Junkie]

Getting shocked from the residual HeNe charge is like getting a static shock. Although it's not painful, it could trigger a reflex if you don't expect it. However, touching both the anode and cathode while the laser is powered is painful.

From what I've read its very painful. :thinking:

I'll have to see for myself when I dig out my tube. :tinfoil:

 

[james1095]

The charge can stick around for a surprising amount of time. I've been zapped by both tubes and power supplies days after they were last powered.

It hurts, how much varies, but it is not pleasant. It's happened to me far too many times, and feels a lot like those really bad static zaps you can get in the middle of winter if you wear a fleece sweater or scuff your feet around on carpet. It probably won't kill you, but it might result in your laser smashing on the floor. Better to be safe and short the pins to discharge.

 

[Wolfman29]

Less bad or worse than touching the recently fully charged huge caps on a computer power supply? I took a power supply apart and accidentally got zapped by the caps a couple hours after taking it apart... boy was that unpleasant. My arm was numb for like an hour.

 

[james1095]

Way less painful than that. The fully charged caps in a computer power supply are actually quite dangerous, people have died from that sort of thing, potentially up to 340VDC and capable of brief discharges of hundreds of Amps.

The capacitance of a HeNe tube is in the picofarads, and the caps in the output of a HeNe power brick are a few nF. Higher voltage but nowhere near the energy storage capacity.

 

[Wolfman29]

Yeah. That one really hurt like a bitch :\ Learned my lesson after that one to wait a couple of days after removing a PSU. I guess I got lucky

 

[james1095]

Discharging them yourself is always safer than waiting. I have a couple of probes attached to a 10 ohm 5W resistor that I use for this. The value isn't critical at all, but something in the range of 5 to a few hundred Ohms will discharge most capacitors in less than a second without blasting chunks out of anything.

 

[Wolfman29]

Hmm. Never thought of that. What wires do you hook up to the assembled PSU in order to discharge the large caps? Because taking it apart to find the leads for the caps is what *lead* to the shock, so I don't want to do that again

 

[james1095]

I touch the probes right to the capacitor pins on the bottom of the PCB. There is still some risk, but I've been doing this long enough to know what I can get away with

 

[icecruncher]

Way less painful than that. The fully charged caps in a computer power supply are actually quite dangerous, people have died from that sort of thing, potentially up to 340VDC and capable of brief discharges of hundreds of Amps.

The capacitance of a HeNe tube is in the picofarads, and the caps in the output of a HeNe power brick are a few nF. Higher voltage but nowhere near the energy storage capacity.

I wouldn't count on that. This is straight from Sam's Laser FAQs hene page.

(From: Doug (dulmage@skypoint.com).)

Well, here's where I embarrass myself, but hopefully save a life...

I've worked on medium and large frame lasers since about 1980 (Spectra-Physics 168's, 171's, Innova 90's, 100's and 200's - high voltage, high current, no line isolation, multi-kV igniters, etc.). Never in all that time did I ever get hurt other than getting a few retinal burns (that's bad enough, but at least I never fell across a tube or igniter at startup). Anyway, the one laser that almost did kill me was also the smallest that I ever worked on.

I was doing some testing of AO devices along with some small cylindrical HeNe tubes from Siemens. These little coax tubes had clips for attaching the anode and cathode connections. Well, I was going through a few boxes of these things a day doing various tests. Just slap them on the bench, fire them up, discharge the supplies and then disconnect and try another one. They ran off a 9 VDC power supply.

At the end of one long day, I called it quits early and just shut the laser supply off and left the tube in place as I was just going to put on a new tube in the morning. That next morning, I came and incorrectly assumed that the power supply would have discharged on it own overnight. So, with each hand I stupidly grab one clip each on the laser to disconnect it. YeeHaaaaaaaaa!!!!. I felt like I had been hid across my temples with a two by four. It felt like I swallowed my tongue and then I kind of blacked out. One of the guys came and helped me up, but I was weak in the knees, and very disoriented.

I stumbled around for about 15 minutes and then out of nowhere it was just like I got another shock! This cycle of stuff went on for about 3 hours, then stopped once I got to the hospital. I can't even remember what they did to me there. Anyway, how embarrassing to almost get killed by a HeNe laser after all that other high power stuff that I did. I think that's called 'irony'.

Anyway, nice hene, and be careful! I have extra reason to say that. I have a pacemaker. So it's even more dangerous for me!