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

 

[Aidan345733]

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

I’m

 

[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?

 

[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.

 

[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]

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]

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.

 

[anorlunda]

Thread reopened.

 

[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]

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.

 

[Aidan345733]

Sorry that second video was supposed to be this:

 

[anorlunda]

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?

 

[berkeman]

I am going to supply 120 vac from an electrical outlet

Can you say a few words about how you will make this connection to 120VAC Mains power safely? Where will you place the switch, will it be single pole or double pole? What fuse rating will you use and why? How will you handle the Line lead differently from the Neutral lead? Will your use of the AC Mains be singly-insulated or doubly-insulated? How does that affect whether you use a 2-prong or 3-prong power cord? How can the use of an AC Mains Isolation Transformer be useful in some test setups?

If you don't know the answers to those questions by heart, you should not be tapping into the AC Mains directly as a power source.

 

[Rive]

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

As I see the OP is not really good with clarifying matters and giving answers. With that we does not even know how he want to utilize the line voltage. Directly powering the primary coil? Putting the 120V AC to the transistor? Adding some kind of power supply what he just forgot to mention? The possible consequences are quite different and I don't think we have to take the risk to guide an unwilling pupil here...

The key point is that with the involvement of the line voltage no part of this circuit can be considered safe any more. Adding in any details about why and how at this point makes no difference and feels like wasted effort. It does not feel like the OP could be trusted either.

 

[Aidan345733]

I understand your concerns and take them seriously, especially since others will be around this apparatus. I will not connect directly into the AC mains but I was planning on using the 120 volts that is standard in most outlets using a proper transformer that I have acquired. The connected wire will be double insulated and will have a three prong connection in the outlet. And I will continue to do the calculations and ensure that the circuitry is plenty strong enough to handle such power.

 

[anorlunda]

I understand your concerns and take them seriously, especially since others will be around this apparatus. I will not connect directly into the AC mains but I was planning on using the 120 volts that is standard in most outlets using a proper transformer that I have acquired. The connected wire will be double insulated and will have a three prong connection in the outlet. And I will continue to do the calculations and ensure that the circuitry is plenty strong enough to handle such power.

Forgive our directness, but what you've shown us so far do not impress.

Hand waving, "I'll put in a transformer," is not persuasive unless you have to skills to ensure that there is no chance for a short circuit between primary and secondary. The picture of your original layout looks as unsafe as it could be.

You have not commented on this;

The only Tesla coil I've seen IRL (at the Griffith Observatory in LA) was safely enclosed in a Faraday cage.

You are getting ideas from Youtube videos from amateurs with unknown credentials. Now you are departing from those instructions.

Even when there is only one person in a project, a "culture of safety" is still needed.

PF members: If we were to write a "safety code" for such a project, what would it say?

 

[Aidan345733]

I guess all I can comment is, the pictures you saw before were incredibly messy and certainly unsafe. Once the series vs parallel problem was worked out I fixed everything before ever applying power again. The Tesla coil at the Griffith Observatory has millions of volts for output and is at least quadruple the size of mine. The YouTube videos were not where I was getting all of my information just references to what others have done. As to the transformer concern that was just a statement. I have a proper power source now, not some batteries on a table. I have everything properly insulated now and there is a metal rod that is grounded right near the plasmatic discharge to catch any sparks that could cause a short circuit between the coils. Going any further safety is a MUST and I don’t take lightly to the actual possibility of anyone getting hurt by carelessness. The whole reason this post is still open is because people need to see how to safely do any kind of project with high voltage and for people to comment on higher power rated parts so I can continue this project as safely as possible.

 

[berkeman]

I will not connect directly into the AC mains but I was planning on using the 120 volts that is standard in most outlets using a proper transformer that I have acquired.

It's good that you plan to use a transformer to isolate the AC Mains connection from your application circuit. But you still did not address the Line/Neutral question, the Switch question, or the Fuse question that I asked. That's worrisome for me.

The connected wire will be double insulated and will have a three prong connection in the outlet.

The wire insulation is only a small part of the safety aspects of using such a power source. If your transformer is doubly-insulated and you use other proper construction techniques, then the 3-prong power cord is not needed. If you use a singly-insulated power supply design, then you generally will need to use a 3-prong power cord and attach the Earth Ground wire to your project in some very particular ways.

I would recommend that you just use a pre-made 120V/24VAC transformer that already has appropriate UL safety approvals (or other agency approvals, depending on where you live). That is by far the best approach for your early electronics projects, until you can find a local Mentor to help you with safety aspects of higher-voltage AC Mains based projects. You can use such a packaged transformer for many of your DIY projects going forward. They are available in many power levels at reasonable prices.

https://cdn3.volusion.com/czamo.vpczb/v/vspfiles/photos/115-24VAC1000-4.jpg?1492079340

 

[Aidan345733]

I believe I have the power source problem is mostly dealt with but there is still the concern on what MOSFET to use, it must be high power and extremely fast switching, and how much I’m expecting to need the resistor to stand up to without burning. I will definitely consult a local professional for all upcoming projects that involve electrics.

 

[anorlunda]

We can't expect DIY projects to meet the same standards as professional laboratories or work shops. But neither should we offer advice to DIY projects that may cause injury or worse.

The primary safeguard is to see that the DIY project has oversight from an experienced mentor. Sometimes, local hobby clubs can provide that.

The first thing that the mentor can do is to compare the skills of the hobbyist with the intrinsic dangers of the project. In a case such as this one, I would advise the OP to abandon the Tesla Coil project, and to choose a less risky one.

The second thing for the mentor is to look for the many ways that things can go wrong and to suggest to the hobbyist ways to avoid them or to mitigate them.

Online public discussions with strangers is no substitute for a face-to-face relationship with a mentor.

So, I'm going to enforce PF's rule forbidding public discussion of dangerous topics. Thread closed.