My Tesla coil doesn't work properly using slayer exicter

Thread Starter

MerryGR

Joined Jul 21, 2019
17
Hi folks, today I tried to make my own Tesla coil circuit according to the schematic below, except that I have changed the number of turns on the secondary and primary so could get a higher output voltage (1 to 500+ turns). That's what I was trying to do. But I have come across a problem. I used Power transistor (BD243C) instead of the 2222A. I wired up my circuit according to the schematic below with red LED, 9V battery but without switch to see if it's at least working.

The circuit doesn't work as expected. My LED didn't light up, transistor is heats up. There are voltage drops in the circuit which I probed but no sign of high voltage output. Can anyone notice something weird and tell me?



Thanks to everyone who post a sensible and helpful answer.
 

djsfantasi

Joined Apr 11, 2010
5,705
Well, if that schematic is accurate, you have the LED wired backwards...

When do you expect the LED to light? It’s hard (impossible) to determine the wiring to the 9V battery in your pic. It’s possible that if the coil lead in your schematic is providing -7V then the LED might light. For a microsecond before it burns out since there is no current limiting. But I can only see two connections to the coil in your pic.
 

bertus

Joined Apr 5, 2008
20,109
Hello,

The schematic shows an exitating coil of 3 turns, you only have one.
Also that coil could be connected the wrong way around.

Bertus
 

Thread Starter

MerryGR

Joined Jul 21, 2019
17
Well, if that schematic is accurate, you have the LED wired backwards...

When do you expect the LED to light? It’s hard (impossible) to determine the wiring to the 9V battery in your pic. It’s possible that if the coil lead in your schematic is providing -7V then the LED might light. For a microsecond before it burns out since there is no current limiting. But I can only see two connections to the coil in your pic.
I connected anode to the emitter of the transistor and cathode to the collector. When I use my multimeter to test if it's backwards, it's not because the LED lights up.
 

Thread Starter

MerryGR

Joined Jul 21, 2019
17
Well, if that schematic is accurate, you have the LED wired backwards...

When do you expect the LED to light? It’s hard (impossible) to determine the wiring to the 9V battery in your pic. It’s possible that if the coil lead in your schematic is providing -7V then the LED might light. For a microsecond before it burns out since there is no current limiting. But I can only see two connections to the coil in your pic.
It's not connected the wrong way, I tried swapping the leads and still doesn't work. So should I add more turns to the primary?
 

djsfantasi

Joined Apr 11, 2010
5,705
I connected anode to the emitter of the transistor and cathode to the collector. When I use my multimeter to test if it's backwards, it's not because the LED lights up.
First, that’s not what’s shown in your schematic. You have the LED cathode connected to the base of the transistor. And the anode if the LED is connected to the emitter and ground.

The LED is a) reverse biased, the cathode should be connected to the lower voltage node, ground in this case. You have it connected to +9V. And b) without current limiting, the first time you connected the battery in your schematic, the LED went *poof*!
 

Thread Starter

MerryGR

Joined Jul 21, 2019
17
First, that’s not what’s shown in your schematic. You have the LED cathode connected to the base of the transistor. And the anode if the LED is connected to the emitter and ground.

The LED is a) reverse biased, the cathode should be connected to the lower voltage node, ground in this case. You have it connected to +9V. And b) without current limiting, the first time you connected the battery in your schematic, the LED went *poof*!
Am I supposed to desolder the LED and swap the leads + add a resistor?
 

djsfantasi

Joined Apr 11, 2010
5,705
I would... after you confirm that the anode is connected to ground on the battery.

Or, go over you circuit as wired and if it’s different than the schematic you posted, update the schematic and post the corrected version.
 

Thread Starter

MerryGR

Joined Jul 21, 2019
17
I would... after you confirm that the anode is connected to ground on the battery.

Or, go over you circuit as wired and if it’s different than the schematic you posted, update the schematic and post the corrected version.
Sir, I already told you my anode is connected to the ground of the battery, I even tested it with my multimeter.. i put the positive lead of the multimeter to the anode which is connected to the emitter which is then connected to the ground of the battery. LED light up in that direction, when I tried backwards (what you tried to tell me) it didn't work because it was reverse biased. From your perspective it might seem different because my photo is badly taken but everything is wired correctly as I traced my steps back almost 5 times and my wiring matches the picture's wiring.

Might there be problem with my secondary coil? You see, I was wiring it, overlaping the first layer sometimes. Also when I was constructing the secondary coil, I accidentally pushed too hard and broke the wire and had to tie it together.. but it was a small knot and I continued wiring.. could this be the problem? Coil looks like this.

 

Alec_t

Joined Sep 17, 2013
10,470
I accidentally pushed too hard and broke the wire and had to tie it together..
Unless you removed the enamel insulation from the wire, just tying a knot won't make electrical connection between the two broken ends. The enamel needs to be removed and the two ends soldered together.
 

Thread Starter

MerryGR

Joined Jul 21, 2019
17
I could somehow clip off the tied wires, use fire to get rid of the insulation and then solder it together, right?
 

Thread Starter

MerryGR

Joined Jul 21, 2019
17
And I have already told you, the LED won’t light if it’s anode is connected to ground. The cathode needs to be connected to ground or the LED won’t light.
Alright :D I will look into it tomorrow, I'm tired now. I'll cut the wire, clean it and solder it for proper connection on secondary. Then, i will swap the LED and let you know how it works.

Turn notifications here so I can inform you :) in case I need more help.
 

djsfantasi

Joined Apr 11, 2010
5,705
Alright :D I will look into it tomorrow, I'm tired now. I'll cut the wire, clean it and solder it for proper connection on secondary. Then, i will swap the LED and let you know how it works.

Turn notifications here so I can inform you :) in case I need more help.
Good.

If it still doesn’t work, ask yourself if you have any current limiting into the LED and if you do, is the current limited to a value which won’t light the LED.

You have a 22k resistor in series with the LED. This will limit current to 0.3mA. A typical red LED requires 20mA. Do you see an issue?

With a 9V supply, you need a 360Ω resistor in series with the LED. Wire the LED and a 360Ω resistor in series, connect the cathode to ground and the other end before the 22kΩ resistor.
 

be80be

Joined Jul 5, 2008
1,945
I slapped one of these together it did osculate and put Electromagnetic (EM) radiation i guess that be what you call it LOL
the little gadget on my DVM reads Electromagnetic (EM) radiation simple little thing to make just 2 diodes 2 cap's and 10 k resistor

Here a copy of the EM tester L1 is the antenna
The diodes have to be 1n34a
rft.png
 
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Thread Starter

MerryGR

Joined Jul 21, 2019
17
Nothing still works.. I tried everything you told me here.. Is there a problem with my secondary? I told you I overlapped one layer with another most of the times.. some say it's not good to do that. I even used the PN2222A transistor.
 

bertus

Joined Apr 5, 2008
20,109
Hello,

Do you have an old AM radio?
Hold it near the coil and listen to the difference in noise when the coil is on or off.

Bertus
 

Alec_t

Joined Sep 17, 2013
10,470
And I have already told you, the LED won’t light if it’s anode is connected to ground.
I'm not so sure. With the LED connected as shown, if the oscillator is working the negative swing of any voltage induced in the secondary coil could light the LED. Inverting the LED would not allow it to light (except perhaps very faintly), because it would be shunted by the base-emitter junction.
 
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