LASER Power Supply

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If you have ever worked with lasers, you know how fun and interesting it can be, you also know how expensive it can be. The high voltage power supplies for the laser tubes are often more expensive then the tubes themselves. This supply can be built with commmon parts, most of which you probably already have in your junk box. The secret is the transformer used. It is a common 9V 1A unit, connected backwards for step up.

Please note that some people may have trouble with this supply. This is due to the slight difference in transformers. For more information on LASER power supplies, take a look at Sam Goldwasser's Laser Supply Info Page.

Schematic

Parts

Part	Total Qty.	Description	Substitutions
R1	1	10 Ohm 10W Or Greater Resistor
R2	1	Ballast Resistor, See "Notes"
D1, D2, D3	3	1N4007 Silicon Diode
C1, C2, C3	3	0.1 uF 2000V Capacitor
T1	1	9V 1A Transformer
S1	1	115V 2A SPST Switch
MISC	1	Case, Wire, Binding Posts (for output), Line Cord

Notes

T1 is an ordinary 9V 1A transformer connected backwards for step up.

R1 MUST be installed on a LARGE heatsink. A good heatsink is the metal case the supply is built in.

R2 Protects the laser tube from excess current. It should be soldered directly to the anode terminal on the tube. To find R2, start with a 500K 10W resistor and work down until the tube lights and remains stable.

If you have trouble with the tube not starting easily, use a longer anode lead that is wrapped around the tube.

Depending on the transformer you use, the circuit may or may not work. I cannot guarantee the operation of this circuit. Build at your own risk. Some transformers contain very few secondary windings which will quickly saturate the core and basically act like a direct short. The more secondary windings (that is, primary in this circuit) the better.

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Comments

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barath LASER Power Supply Thursday, October 28, 2010 10:21:27 AM

i did your transformer inverse thing , the primary shorted out and blew my mains out !!!!
(Editor's notes: Use a series inductor to limit current. )

Hafeez LASER Power Supply Monday, February 23, 2009 2:22:04 AM

sir, this is a good project. actually i am a laser sub engineer in paksitan and want to work practically on lasers.

Pawpamayer LASER Power Supply Tuesday, November 18, 2008 12:07:37 PM

phamducduy The 9 volt side of the Transformer is connected to the 115 volt line thus causing the stepup effect

Techineer LASER Power Supply Saturday, October 25, 2008 1:40:41 AM

While theoretically this should work, the main concern I have is that the transformer primary winding (being used as the secondary) is designed for 120V AC and the insulation materials in the windings and the core may not be sufficient to withstand the interwinding voltages and electric fields produced by peak voltages up to 2250 volts. (120V x 120/9 x 1.414) I would expect to hear some sizzle and possibly see smoke coming from the transformer. Depending on how the transformer is mounted, you might also see arcing to the frame. Use with caution and don't touch the transformer when operating!

Old Guy (retired EE) LASER Power Supply Wednesday, October 01, 2008 3:37:37 PM

The one answerer, who said there would be only 9 volts on the output, appears to have missed that the transformer is reversed, so it is a 13:1 step-up, rather than step-down. If we could drop the entire voltage across the input coil (which would normally be a 9v. winding) we would get 115 x 13 = 1495 volts. The problem with this circuit is that too much current flowing through that input coil will burn it out immediately. While this will depend entirely on the transformer selected (that is, the impedance of that coil, which in an AC circuit acts like resistance in a DC circuit) I do not believe a ten-ohm series resistance is sufficient here. If the coil impedance is very low, most of the voltage drop is across the resistor, leaving a lower effective voltage across the coil, and thus the output will be significantly lower as well. (The resistor can take it if it is high enough wattage and well sinked.) As you raise the impedance of the coil to achieve a higher output voltage, you also raise the voltage drop across this very low-current coil in order to give a higher output voltage, you increase the wattage that the transformer must sink to keep from burning up. Overall, this CAN work if you are very selective of the parts used, but anyone building it also has a very good chance smoking the whole project. You might be able to improve the performance but placing a small capacitor in series in the input, but I would do the whole thing differently in the first place. Thanks. Anyone who needs help can contact me thru email and I will try to help your individual needs.

Pawpamayer LASER Power Supply Thursday, June 26, 2008 7:53:18 PM

I have a Melles Griot 65 mw laser tube. The box says its Melles # HR551-64 size 15 1/16 X 1 3/4 pwr out 8mw Beam Divergence 2.50mRAD power required 1.7 - 2.45 KVDC @ 6.5ma And I'm looking to build a power Supply for it Any sugestions?

mike lynn LASER Power Supply (OTHER) Monday, January 28, 2008 9:14:56 PM

what kind of lasers are used for the power supply.

revannath LASER Power Supply Monday, January 07, 2008 3:45:28 AM

sir, this is very good project thank you.

anonymous LASER Power Supply Thursday, December 27, 2007 9:11:46 AM

thanks very much

anonymous LASER Power Supply Monday, December 17, 2007 3:11:01 AM

Looks like people are running off-tangent with a lot of twisted theory! The Circuit CAN work , pretty well!! James Martin: Dont go by assumptions. Current is Drawn by the load. dont think you know the Laser, but it is 2mW!! Even if the O/p current is 1mA, you can see that the I/P current is fairly small. Some thing like 1W , without the relevant electronic calc. anonymous: Learn physics first, along with good English. The 1N4007 is rated for 1KV max. 3 in series will stand the o/p voltage of 3KV. since the output is 1500V, the diodes have a good chance of surviving the RMS values. ( or even the peak value). Guys : Please stop commenting about anything, without some serious homework!

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barath	LASER Power Supply	Thursday, October 28, 2010 10:21:27 AM
i did your transformer inverse thing , the primary shorted out and blew my mains out !!!! (Editor's notes: Use a series inductor to limit current. )
Hafeez	LASER Power Supply	Monday, February 23, 2009 2:22:04 AM
sir, this is a good project. actually i am a laser sub engineer in paksitan and want to work practically on lasers.
Pawpamayer	LASER Power Supply	Tuesday, November 18, 2008 12:07:37 PM
phamducduy The 9 volt side of the Transformer is connected to the 115 volt line thus causing the stepup effect
Techineer	LASER Power Supply	Saturday, October 25, 2008 1:40:41 AM
While theoretically this should work, the main concern I have is that the transformer primary winding (being used as the secondary) is designed for 120V AC and the insulation materials in the windings and the core may not be sufficient to withstand the interwinding voltages and electric fields produced by peak voltages up to 2250 volts. (120V x 120/9 x 1.414) I would expect to hear some sizzle and possibly see smoke coming from the transformer. Depending on how the transformer is mounted, you might also see arcing to the frame. Use with caution and don't touch the transformer when operating!
Old Guy (retired EE)	LASER Power Supply	Wednesday, October 01, 2008 3:37:37 PM
The one answerer, who said there would be only 9 volts on the output, appears to have missed that the transformer is reversed, so it is a 13:1 step-up, rather than step-down. If we could drop the entire voltage across the input coil (which would normally be a 9v. winding) we would get 115 x 13 = 1495 volts. The problem with this circuit is that too much current flowing through that input coil will burn it out immediately. While this will depend entirely on the transformer selected (that is, the impedance of that coil, which in an AC circuit acts like resistance in a DC circuit) I do not believe a ten-ohm series resistance is sufficient here. If the coil impedance is very low, most of the voltage drop is across the resistor, leaving a lower effective voltage across the coil, and thus the output will be significantly lower as well. (The resistor can take it if it is high enough wattage and well sinked.) As you raise the impedance of the coil to achieve a higher output voltage, you also raise the voltage drop across this very low-current coil in order to give a higher output voltage, you increase the wattage that the transformer must sink to keep from burning up. Overall, this CAN work if you are very selective of the parts used, but anyone building it also has a very good chance smoking the whole project. You might be able to improve the performance but placing a small capacitor in series in the input, but I would do the whole thing differently in the first place. Thanks. Anyone who needs help can contact me thru email and I will try to help your individual needs.
Pawpamayer	LASER Power Supply	Thursday, June 26, 2008 7:53:18 PM
I have a Melles Griot 65 mw laser tube. The box says its Melles # HR551-64 size 15 1/16 X 1 3/4 pwr out 8mw Beam Divergence 2.50mRAD power required 1.7 - 2.45 KVDC @ 6.5ma And I'm looking to build a power Supply for it Any sugestions?
mike lynn	LASER Power Supply (OTHER)	Monday, January 28, 2008 9:14:56 PM
what kind of lasers are used for the power supply.
revannath	LASER Power Supply	Monday, January 07, 2008 3:45:28 AM
sir, this is very good project thank you.
anonymous	LASER Power Supply	Thursday, December 27, 2007 9:11:46 AM
thanks very much
anonymous	LASER Power Supply	Monday, December 17, 2007 3:11:01 AM
Looks like people are running off-tangent with a lot of twisted theory! The Circuit CAN work , pretty well!! James Martin: Dont go by assumptions. Current is Drawn by the load. dont think you know the Laser, but it is 2mW!! Even if the O/p current is 1mA, you can see that the I/P current is fairly small. Some thing like 1W , without the relevant electronic calc. anonymous: Learn physics first, along with good English. The 1N4007 is rated for 1KV max. 3 in series will stand the o/p voltage of 3KV. since the output is 1500V, the diodes have a good chance of surviving the RMS values. ( or even the peak value). Guys : Please stop commenting about anything, without some serious homework!