Does a CO2 laser tube need a ballast resistor like the old HeNe tubes ?? I hooked my up and toasted the power supply in seconds even with the current set at minimum.
Mike
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Does a CO2 laser tube need a ballast resistor like the old HeNe tubes ?? I hooked my up and toasted the power supply in seconds even with the current set at minimum.
Mike
The power supply should have one in it. If you made the power supply that you need a ballast.
good question. my co2 laser is rf excited so it's not the same at all.
Holy Fuck! That is tiny! It looks like a YAG!
Ben --
I got the supply off Fleabay. No schematics.... I did have the HV transistors to repair it though. At 15 mA, is 1K enough !! Maybe 15K would stablize it better. Only 3.3 watts disipation.
Mike
Try 50k ohm. Make sure the wattage is >10W
Ben --
I have 2 - 25K , 10 Watt resistors. Should help. I have plenty of volts available - Up to 14 KV ... Maybe I should go higher yet - It will still ignite.
Mike
it is very much like a lady's purse model laser..Quote:
Originally Posted by Laser Ben
Ben --
I wii start with the 2 - 25K resistors. The voltage drop accross each is just under 400 volts -- Should be safe there.
SD -- That's a super little laser !! If you are cutting in those pix, is there gas assist ?? How many "KW" !!! Where did you find a toy like that ??
Mike
OOPS -- I put in a 50K resistor and it draws about 25ma .... Burned through a 1" piece of foam rubber and then smoked a table 4' away !! No Lens !!!!! 1/4" beam.
Thanks for the advice !!
Mike
Hope you got your IR goggles on :cool: :D
Glass-lens eyeglasses should work pretty well...Quote:
Hope you got your IR goggles on
CO2 lasers lase in the far IR; 10,600 nm or something like that. At that wavelength glass is opaque to the radiation. (Which is why your car gets hot in the summer - short wave solar radiation gets in, but the longwave IR coming off the seats and dash can't get back out.)
On the other hand, your standard plastic IR goggles (1064nm and 808 nm) would be just about useless. (They'd melt and catch fire in short order.)
Adam
Yeah I was talking about 10.6 uM protection. The liquid in the eye looks black to that wavelength and causes serious damage
How many watts is the tube rated to?
WTF? maybe if the lady looks like Arnold S...:)Quote:
it is very much like a lady's purse model laser..
it weighs less, not including the 28vdc 6amp power supply, than some purses!Quote:
Originally Posted by steve-o
have you seen my free trial sized flamethrower?
Free? Wow . put me down for 100;)
What is that? A super-soaker water gun filled with gasoline?
I want one!
But back to Laser Ben's question... How much power can you push out the business end of your CO2 laser, Mike?
Adam
Sounds very fun and dangerous to me:)Quote:
What is that? A super-soaker water gun filled with gasoline?
I don't think I'll go try it..
Yeah...
I saw a video on YouTube where some guy had filled a super-soaker with a flammable liquid (don't know if it was gasoline or something else), and he was shooting liquid fire all over his backyard. But it didn't look quite as impressive as the picture above.
I'm thinking he's got some sort of pressurized hose feeding that wand and the main tank is out of the picture. But it sure looks cool. (Not that I'd actually try to build one myself... With my luck the gasoline would dissolve the plastic parts of my makeshift flamethrower and I'd end up setting myself on fire.)
Adam
OH, you would have liked to see mine! ~100 with denatured alcohol in a nitrogen fed tank. The jet is lit by a MAPP torch. Quite impressive! And all concealed in a backpack!
Good stuff on this thread !! BOTH things are fun !!!
My CO2 is a fleabay 15 watt sealed tube about 18" long. I've got to get the current down somehow because it's rated at about 12 mA NOT the 20 mA I'm getting. I don't think the current control in the PS is working.
Mike
There is a "safer" ;)flame-thrower cartrige that is loaded into a 12 ga shotgun that blasts a flame a hundred feet or so for 3-4 seconds setting everything it touches on fire. Good way to burn the house down..
and the neighborhood too-:p
Yes, but with mine you get a continuous stream of liquid flame.
Any pics?................
Yes, I'll post them tonight.
Steve --
Those shotgun shells are called "Dragon Breath". Illegal in some states like Iowa. I believe they are full of thermite. I wouldn't risk a good gun with one.:mad:
Mike
Anyone have a schmatic for a Line Lite Laser model 941S power supply ??
I don't have enough control of the current.
Mike
uhhh- nope I wouldn't either.Quote:
I wouldn't risk a good gun with one.
Mike- sorry we're getting off topic here aint we:o
I'm no CO2 expert but seems if you increased the ballast resistor you could get the current down. I=E/R and all that. What is your present voltage, current, and ballast resistor value? Maybe we can figure out the correct resistor you need- including the wattage.
Well -- If this went off course, it is fun stuff !!!!
I've been increasing the ballast resistors to almost 100K !!! I'm also using a Variac on the power line. I'm a bit afraid to use a light dimmer for the power control because of the noise they produce.
Mike
How much was that tube and power supply? I want one!
Ben --
The 15 watt tubes are $199 on the "bay".... You are on your own for power supply. A neon sign xfmr and some HV diodes, capacitor PLUS a ballast resistor and you get flame !!
Mike
Measurements on my CO2 setup:
Power supply output (limited by a variac set for 75 VAC): 8500 VDC
Ballast resistors: 150 K Ohm - Volts across tube: 6200 VDC
Tube current: ~17 mA.
The tube is rated 7.8 to 9.3 KVDC at 12 - 15 mA.
I think the output voltage of this power supply is too high and can't be regulated this low.
SO - I think that a solid state speed control for a fan is suited to control this inductive load without danger of spikes and/or noise damaging the circuit...
What say, Oh knowledgable minds ???:D
Mike
I'm interested, where exactly can I find one?
eBay. As said before. CO2 Laser Tube. Should work. Put on the watch list, and check completed listings to see likely prices and past sources.
I guess these are the things Robin Bowden cooks his sausages with.
Mike, you might get away with that if the cooling is good, but try a bit more current limit resistance. The tube current is what matters, as with a laser diode current, the voltage will be right if the current is. Not sure how much though resistance to add though, maybe another 20K. If you add 100K, you will probably bring the current within the control range of that variac. If you can get solid carbon composite resistors, do it, film types (carbon OR metal) won't work, they'll arc over and burn. There are ceramic types that will also work, but they're rare and maybe expensive. Some kind of cermet or something.
Yo Doctor --
My first Laser was a CO2 which I built 30 years ago !! What a monstrosity !! I still have it ............
I've increased the ballast resistance up to 150 K ohm and this ebay PS keeps pumping out more watts ... The feedback circuit seems to not work as the Vbe on the final driver transistor stays at 0.8 volts no matter what. It seems locked ON.
A variac is a big POS so I thought a 6 amp fan control would work because it's made for an inductive load. I'm trying to make this look good and not like a breadboard kludge. Added resistors simply allow the PS to output to the max and then have excess power burned off as heat in the ballast.
That's why I'm looking for a schematic for this 941S PS. It's max output is supposed to be 15 mA and I don't want toast in there.
Mike
Point taken. That schematic will be needed (or some good reverse engineering), I didn't realise it was trying to maintain some control system, thought only the variac and the limit resistor were controlling current. That 0.8V could be a fault, or a value the control circuit is designed to maintain. If you can find out which without the schematic, you might get the rest sorted too. A post to alt.lasers is often good for rustling up schematics...
Doctor --
Without reverse engineering, the PS appears to control a rectified power line voltage to a HV module. The final driver transistor seems to stay fully biased ON no matter what I do. This is a hard circuit to trouble shoot when the module is putting out over 12 KV !!!
I'm saying screw the current control and limit the input with the 6A fan control. If it can't pull it in, It can't put it out !!
How do I get to this alt.lasers ???
Mike
If any part of that circuit is effectively a power converter, then even limiting the input might not be so easy, it might just try to draw more amps if the input volts are lowered..
alt.lasers is being mentioned in a new thread in the lounge... There's enough info there now to get you there quickly. I strongly suggest a newsreader over Google Groups, as it's the best way to learn it, but Google Groups is good for emergencies.
What you might get is an alternative idea for PSU.. I've read that people get results with neon transformers. Not sophisticated, but cheap, and easier to predict their behaviour. I guess your first CO2 might have used one? :)
Doc --
My first CO2 was (is) 3' long and powered by a BIG neon sign Xfmr with a voltage doubler and variac. This "little" supply does limit OK with a variac. Will a light/fan dimmer/speed control work OK ?? I think it will because the input is AC line rectified to a capacitor -- A small transformer circuit provides LV to the circuit. The triac switching noise should filter out after a FW bridge and capacitor.
Mike
It might work ok. While a lamp dimmer isn't stern enough to handle input to inductive loads, except maybe brushed motors, there is a similar thing made for various standard mains currents, used for brushed motors and transformers.
rswww.com (RS Components) have something, stock number 655-644, with datasheets you can get for free with no sign-up.
That needs a filter (with a larger inductance than in a lamp dimmer) added to reduce EMI and RFI though, and you'll probably still hear noise in the transformer and maybe have to watch that it doesn't overheat.
I don't know what else to suggest, apart from something like a neon transformer but smaller, fed by a chopper circuit with a frequency of a couple of hundred KHz. Which is probably what that circuit is doing anyway.
Doc --
Looking at this circuit, it looks like a basic full wave bridge input supply ( like a computer supply) with a big cap at 250 volts. The supply then feeds an encapsulated module with volts in / out. The regulator acts as a limiter between the filtered DC and the module. Switching noise from a "dimmer" should get filtered out. Motor speed controlers for fans seem to rely on a power factor shift using caps but I don't think that's needed because of the input configuration.
Mike
I think V b-e will always read .7 or .8 in a grounded emitter circuit (npn). Is the load on the collector side? I have a thyristor fan control module also (looks like a lamp dimmer) I've resisted using it for any kind of inductive load control because of the size of the power device. It is very small. Looks inadequate. Thyristors (scrs and triacs) turn on/ off / both (depending on the device) at zero crossing only, making for a less than precision control.
Ok for fans and heater elements. I'm sure you could try it for transformer control but Power Companies are funny about customers chopping their sine wave up-I learned this the hard way by removing the center out of the 60 Hz wave with an IGBT (@ 10A -powering an argon laser) and 2 seconds later a pulse came back, all the lights got real bright in the house, blew the movs out of all the power strips, took out the microwave oven and the stove. I had some repairing to do after that little experiment:rolleyes:
Steve --
Power factor is a wierd thing about AC power. Fan controls use it by adding capacitors into the feed to the motor.
All I want is a schematicfor this damn 941S power supply !!!
Mike
I guess you are talking about the winding for the run cap, or the start cap for single phase AC motors?
I did a quick dogpile search for "Laser Lite" and couldnt even find the company. What country are they in?
I don't think he is... I think he means that if a PWM type triac circuit can cope with such, it should cope with the input to his supply. I don't think that's the answer though, or at least not all of it. That supply appears to be trying to regulate. Either that needs to be understood and modifed (needs schematic or reverse engineering), OR the internal regulation must be understood at least enough to override it permanently so that another means of regulation can be applied, that won't be fighting with the existing one.
I can't advise further cos I'm in the same position as Mike, worse even, I can't even see a PSU in front of me. I can see several actually, but that's beside the point. >:)
Cheers, Doc:) Is it toddy-time over there?
It should be. Dram time, at any rate... Sadly, not much whisky around. I must do something about that.
Tch. A little over 2 hours and its a virginia gin for me:D
Mike--Can u take a close-up picture of this thing- we might be able to ident something or 2
Steve --
It's an old PS from the alien country of Kalyforinia !! The regulator seems shot so regulating the input should work. I'll bring it up slowly !! I have to turn my coffee table now to average out the burns !!!!
Mike