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Registered Member #4074
Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
Hey everyone, was bored today so I tried building a slayer exciter from parts I had sitting around. Trouble is I can't get the damn thing working!
Its a very simple circuit and I've double checked the connections on everything, but no dice. L1 is 4 turns and L2 is roughly 250-350 turns. I'm using a rectified and smoothed 240V-27V transformer as a power supply and when turned on, the transformer draws a bit less than 100mA at 240V, yet the circuit on the LV side does nothing. The TIP3055 is on a small heatsink but doesn't seem to generate any heat (or not enough to feel).
Sorry for the crap diagram:
I'm quite stumped with this (and feel quite silly, considering how simple the circuit is). Similar circuits on youtube should be able to light a CFL easily, yet I'm not getting any output whatsoever.
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
When I made this circuit it was very temperamental and would only work if L1 was placed just so.
Try reversing L1's direction and reducing the value of the resistor to 22kohm. Also try putting L1 directly around the base of L2 with about 1 inch of space between them and experiment with L1 turns.
The diode I used seemed to make a difference too, I think the UF4007 worked well for me.
Not sure if this would make a difference but can you try a lower supply voltage for now (say 12v), as this worked well for me.
Try those out and see if you get any difference, and if you do get it working see if you experience any RF burns when touching any bare metal connected to the circuit. Every-time I touched the battery terminal I would get the smell of burnt flesh coming from my finger!
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
According to the datasheet for TIP3055, 7V is the maximum permissable emitter-base voltage, but you've got 12V+ fixed bias on your base due to the zener diode, so - at the least - your transistor is permanently switched on, if not perhaps fizzled.
Note that Alex reported some temperamental results using a UF4007 - a plain non-zener rectifier, which would have put just 1.7V on his base.
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
Proud Mary wrote ...
Note that Alex reported some temperamental results using a UF4007 - a plain non-zener rectifier, which would have put just 1.7V on his base.
Actually I had it in reverse with the transistors base and emitter and my exciter worked fine and removing it altogether gave slightly better results. I could get a jet of plasma coming off the end of the L2 coil and could light up a CCFL from around 1 feet away as seen here
I used this diagram for mine
(note L1 and L2 labels are switched around in this one, sorry about the image size too. I didn't upload it).
Registered Member #4074
Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
Hey Alex1M6, your youtube video was what inspired me to fiddle with one of these circuits!
I understand with the 12V base bias the transistor should be fully on, yet I'm not getting an appreciable current draw, and no heat generated anywhere in the circuit. I really should scope it out, but I'm very paranoid about bringing my new digital scope near any experimental circuits.
Should I be using a different transistor? What would be most suitable for this voltage range?
I'll also try experimenting with L1, currently it is 4 turns wrapped directly around the base of L2.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
I don't think your base can be at 12V, initially the base-emitter junction of your transistor will be forward biased and the base will reach ~0.7V with about 800uA flowing through your base biasing resistor. The bulk of the 38V power supply voltage will be dropped across the 470k resistor. The zener is probably there mainly for protection if there's some weird ringing going on perhaps.
The operation idea, I'm guessing, is that as the transistor turns on and applies voltage to the transformer primary this ends up applying negative voltage at the transistor base to turn it back off, making this an oscillator. This will be fiddly of course as only one node of the transformer secondary is connected to the rest of the circuit at the base so the secondary's voltage is really floating with the base of the transistor. Maybe the other side of the transformer secondary is connected to circuit ground, or maybe it relies on some unintentional capacitive or inductive coupling. This is probably why it's hard to get working. And there is a proper orientation for the secondary.
You could always try dropping the base resistors value to get some more gain out of the transistor to see if it will do something, more gain is usually a good idea if your oscillator doesn't oscillate.
Registered Member #5010
Joined: Fri May 25 2012, 07:19AM
Location:
Posts: 1
XravenorX wrote ...
Hey Alex1M6, your youtube video was what inspired me to fiddle with one of these circuits!
I understand with the 12V base bias the transistor should be fully on, yet I'm not getting an appreciable current draw, and no heat generated anywhere in the circuit. I really should scope it out, but I'm very paranoid about bringing my new digital scope near any experimental circuits.
Should I be using a different transistor? What would be most suitable for this voltage range?
I'll also try experimenting with L1, currently it is 4 turns wrapped directly around the base of L2.
Thanks for the help so far.
Hi XravenorX, Try replace your transistor with 2n 3055, get rid of the ZD, replace it with series of 2x1N4148 and a LED, also you may have to add more turns on L2(400-600) and place the L1 on the right spot of L2 (don't wrap L1 too tight, so you can slide it up or down). Currently I'm using 3" diameter/15cm length tube, L2=awg29 700 turns, L1=awg26 15 turns. Transistor I've already use were 2n2222, KSP-06, and 2n3055. All worked well, lite up 50 super white LEDs from 50mA to 200mA, even can produce plasma jet form small incandescent bulb (with ksp-06).
Registered Member #3781
Joined: Sat Mar 26 2011, 02:25AM
Location:
Posts: 701
Maybe you know this already but the distance between the primary and secondary coil matters for these! Try wrapping the primary directly around the secondary coil and if it doesn't work then slowly increase the gap between the two coils until it does.
EDIT: You could try lighting a lower wattage bulb, like a 4 watt. Also, you may need to add a top-load, it significantly increased power output on my SE.
Registered Member #4074
Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
Thanks for the new ideas, I've been thinking of playing with this circuit all week.
I'll try varying the spacing between L1 and L2. Unfortunately don't have any 1n4148 diodes. The only diodes I have are 1n4007, 1n5408 and the zeners, so I guess I'll have to order some.
As for the transistor, I've been thinking of replacing it with a IRF540N. It's voltage and current ratings are a bit better than the 2n3055 (plus I have a whole bunch of them), but is there any reason a MOSFET would be unsuitable?
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