Sigurthr
0
- Joined
- Dec 11, 2011
- Messages
- 4,364
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- 83
If your diode is frying, it is probably because either the peak forward current (Ipf) is being exceeded (I think you said it was rated for 30mA) or the Peak Inverse Voltage (PIV) is being exceeded. More likely is that the Ipf is being exceeded because you said that there is no resistor being used.
Go down to your local electronics shop and grab the largest wattage resistors you can find in various resistance from a couple ohms to 1Mohm (1 million ohms), just put one in series with the HV Diode between the PSU and the Diode. Try to avoid "wire-wound" resistors as the added inductance would probably cause issues. You'll have to experiment with which reistance functions best. I have no idea how much current a TEA laser draws from the NST, so I can't give you a perfect value. I = V / R (remember it is in amps = volts over ohms, so don't forget to divide mA by 1000 for the amps or to multiply kV by 1000 for the volts). At 30kV a 1Mohm resistor will limit the current to 30mA, iirc.
I don't recommend adding a second diode, at least not in series, another one in parallel would not hurt but generally the rule for adding diodes in parallel is to never do it without a series resistor for each diode, since not having one can let all the current flow through only one of the diodes, frying it. So, I suggest you try with the resistor and see how it goes.
If you wanted to make it a bit less noisy you could form a Full Wave rectifier out of HV Diodes and use that in place of the single diode, this would double the pulse frequency of the laser as well. Full Wave Rectification takes 4 diodes, fyi, and is fairly simple to construct. Pull up a simple schematic on Wiki for you and you'll be all set.
Might I recommend trying various fluorescent materials as lasing targets instead of the white paper? Uranium "Vaseline" glass works rather well.
Go down to your local electronics shop and grab the largest wattage resistors you can find in various resistance from a couple ohms to 1Mohm (1 million ohms), just put one in series with the HV Diode between the PSU and the Diode. Try to avoid "wire-wound" resistors as the added inductance would probably cause issues. You'll have to experiment with which reistance functions best. I have no idea how much current a TEA laser draws from the NST, so I can't give you a perfect value. I = V / R (remember it is in amps = volts over ohms, so don't forget to divide mA by 1000 for the amps or to multiply kV by 1000 for the volts). At 30kV a 1Mohm resistor will limit the current to 30mA, iirc.
I don't recommend adding a second diode, at least not in series, another one in parallel would not hurt but generally the rule for adding diodes in parallel is to never do it without a series resistor for each diode, since not having one can let all the current flow through only one of the diodes, frying it. So, I suggest you try with the resistor and see how it goes.
If you wanted to make it a bit less noisy you could form a Full Wave rectifier out of HV Diodes and use that in place of the single diode, this would double the pulse frequency of the laser as well. Full Wave Rectification takes 4 diodes, fyi, and is fairly simple to construct. Pull up a simple schematic on Wiki for you and you'll be all set.
Might I recommend trying various fluorescent materials as lasing targets instead of the white paper? Uranium "Vaseline" glass works rather well.
