Electrical Why isn’t this Tesla coil working?

Aidan345733

Hello all! I have made a Tesla coil using a proven circuit I found online but what I have made isn’t working here is a picture please help.

PS: yes I know it is fairly messy but the specs are as fallows:
B50k potentiometer
One green 5mm led
One 200ohm 1/4 W 5% resistor
Primary coil is 8 turns of 14 awg wire
Secondary is 950 turns of 30awg wire
FJP13007H2TU-ND transistor
And 36-51 dc power supply

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Aidan345733

Here is the circuit, I replace the 50kohm resistor with the potentiometer.
I’m

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Rive

If the components are (still) OK then try switching the polarity of the small coil.

Also, please check those batteries: are you absolutely sure they are connected the right way?

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Aidan345733

I am sure that the batteries are connected properly and the transistor gets warm when I connect power to the circuit so energy is flowing. How do I switch the polarity? Do you mean the by the small coil, the thick wire or the copper wire?

Aidan345733

In the picture it is not connected but when connected nothing happens. The coil doesn’t light up LEDs or fluorescent lights even in direct contact and no visible discharge comes at the top of the coil with or without a top load/toroid.

GrahamN-UK

How do I switch the polarity? Do you mean the by the small coil, the thick wire or the copper wire?
Swap the green lead and the white lead going to the small black coil over. That is, connect the green lead to where the white lead is in the photo and connect the white lead to where the green lead is currently connected. The circuit depends on feedback through the two coils. If the polarity of the feedback is wrong the circuit won't oscillate and hence won't work.

The 9 V batteries in the photo are all connected in parallel giving you 9 V in total. The circuit diagram states a minimum of a 15 V supply. You could connect the batteries into two series-connected pairs, then connect the pairs in parallel to give you 18 V. I'm somewhat sceptical as to whether 4 MN1604 batteries are actually powerful enough for this (but I haven't built one, so what do I know?) Does your source article give a current rating for the supply, as well as a voltage?

Note that if you do get it working it WILL produce dangerous voltages. It would be sensible to google safety precautions for tesla coils and study some of the articles. The only Tesla coil I've seen IRL (at the Griffith Observatory in LA) was safely enclosed in a Faraday cage.

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jrmichler

Also, please check those batteries: are you absolutely sure they are connected the right way?
I'm somewhat sceptical as to whether 4 MN1604 batteries are actually powerful enough for this
Disconnect the batteries, check the battery voltage, then connect the batteries and check the battery voltage again. If the voltage drops too much, then you need a more powerful power supply.

davenn

Gold Member
The coil doesn’t light up LEDs
well, for a start, the LED is reversed biased ( wrong way around) so it cannot light

GrahamN-UK

well, for a start, the LED is reversed biased ( wrong way around) so it cannot light
The LED is fine. It's connected in anti-parallel (in parallel but opposite polarity) with the base-emitter junction of the transistor. Together they provide a return to the negative supply rail for both halves of the AC signal at the bottom of the secondary winding. It'll light up when the circuit oscillates, but not otherwise.

Aidan345733

Yes the circuit is correct, thanks for the input I will definitely work on the voltage and check the wiring to allow for ocilation in the coil.

Aidan345733

One quick update..... I used a 15v dc electric train transformer that I had lying around, the led flashed for a second and then went out and the transistor got very warm. I’m not sure if the transistor is burnt but the led almost definitely is. Any way to tell if the transistor is still good? How should I start with tuning the resistance of the potentiometer before power is aplied to stop this from happening again?

Tom.G

The photo seems to show that pins 1 and 2, the Base and Collector, of the transistor are connected together. They should not be connected to each other.

I question the accuracy of the schematic image regarding the connection of the secondary. To me it does not seem correct.

The schematic image and the wiring in the photograph do not match each other in regards to where the transistor Base connects to the coils.

Turn potentiometer fully counter-clockwise to decrease the likelyhood of burning up the transistor.

Can you supply a link to the site where you found the build instructions?

Cheers,
Tom

Aidan345733

Ok so the transistor wiring is not touching, sorry for the awful picture and angle, the schematic and instructions I fallowed came from . Now in the video no explanation is given as it is done and if you read the comments he states that he actually uses a 180 watt power supply with 40 volts and 4.5 amps to get the plasmatic discharge. Others also expressed their concern for the led, as said before by davenn and he explained it. I knew all of this going in and that is why I believed it would work as shown but a lot of what my inexperienced work shows is how much I inferred into how this is supposed to work. I will continue to fix the wiring and give any updates if there is development.

anorlunda

Mentor
Gold Member
Note that if you do get it working it WILL produce dangerous voltages. It would be sensible to google safety precautions for tesla coils and study some of the articles. The only Tesla coil I've seen IRL (at the Griffith Observatory in LA) was safely enclosed in a Faraday cage.
@Aidan345733 , Before making the circuit work, you need to address those safety concerns. Send me a PM about your safety precautions, and I'll re-open this thread. For now, it is closed.

Mentor
Gold Member

Aidan345733

Ok thanks for the help everyone the circuit is working and everything is safe. I have covered all open wires and ensured even discharge to the batteries I was using. I have a proper power source now and there is a grounded rod to collect unwanted discharge and keep it away from the components. The transistor is on a heat sink and is properly secured.

anorlunda

Mentor
Gold Member
What was the error that prevented it from working?

Aidan345733

I need to use this coil in a demonstration later in the week. I am going to supply 120 vac from an electrical outlet but I am not sure what MOSFET transistor to use and I don’t know the exact number of watts the resistor will need to withstand. Any suggestions on parts or even links on where to buy them would be great.

Aidan345733

The error that prevented it from working was I wound the primary the wrong way, opposite of the secondary, and so the leads had to be switched.

Rive

I am going to supply 120 vac from an electrical outlet
Now, that's a very bad idea. Are you sure you are not thinking on something else?

Any suggestions on parts
Does not matter: in this circuit 120V AC will blow anything to pieces anyway. You should just stick to the schematics (and details) you have started with.

Aidan345733

I was lead to believe that as long as the primary coil is rated to handle the voltage and the parts can handle the input then the circuit will be fine. I was going to use two high power mosfets in parallel and have the resistor go from 1/4 watt to 10-15 watts.

Rive

Are you really thinking about putting this thing to 120V AC from the outlet?

Aidan345733

Right now I have 51 volts going into it and the transistor doesn’t even heat up. The only reason for more power is to have a larger discharge then this:

Also I WILL add a top load I have no intention on killing myself or my electronics.
Here are my references
The second person uses a similar circuit and the first person just demonstrates the principle I was mentioning.

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Aidan345733

Sorry that second video was supposed to be this:

anorlunda

Mentor
Gold Member
I'm very uneasy with the OP's sources and unsure of his skills.

What do others say; is this a safe DIY project for the OP?

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