First Light!

Judging by the title I bet you all very excited to what you will now see! However, don't get your hopes up just yet, there is good news and bad news.

Its been over 2 weeks and I bet your all wondering if the coil is complete, well sort off.

The new HV HC diodes came, they are the biggest and bulkiest diodes I have ever seen and they work a treat. We could only order 2 though even though we needed 3. This is not too much of a problem though as the 2 new diodes are in the voltage doubler circuit and we are leaving the dequing diode as it is. The voltage doubler lowers the current so the dequing diode should be fine as it is.

The new tachometer and hall sensor also arrived, they have been fitted and work great.

Everything was ready for the first test. We ran the coil! There was no output =(. TO be honest this was completely expected, a project of this magnitude was never going to work on the first few tries. 

We then looked over everything to find out where the problem was. We know the tank circuit is working because induction was happening. There was an arc forming at the two ends of the strike rail completing the circuit. We have since covered both ends in insulation to stop this from happening.

We then put a grounded rod next to the topload and an arc formed only about 10cm long. This proves that the circuit is working but is extremely out of tune. We called it a night and focused on analyzing everything to see what the problem is.

This is where are dead line comes in. If you read on of the firsts posts on this blog you will see that we took our small Tesla Coil to a local school to do a demo for an event. That even is yearly and will be taking place next week. Last year we said that the big coil would be done in time, however, the event is getting scarily close and the coil is not done yet. We have spent the past week doing all we can to get the coil ready for Wednesday next week and so have not had time to make posts.

After redoing all of the calculation I found an error. The calculations themselves were right but the figures being inputted were not. It turns out the voltage doubler circuit multiplies the peak AC voltage not the RMS. This means our calculations were off by 3000 volts and so the capacitance was completely wrong. We quickly recalculated it and luckily we could adjust the capacitor bank to match.

However there was yet another problem. Our spark gap motor burnt out. We were saved however when we discovered that we had an old angle grinder we did not need. We completely refitted the spark gap and it is now version 5. This new spark gap is even better though as it can go much faster and easily reaches are desired RPM of 3750. We remounted the hall sensor and fan before fitting it into the cabinet along with the rewired MMC.

We then ran the coil all night long continually testing and tuning different parts of it until we got the best output we could. Here is the biggest official first light.

Its not much yet but at least its bigger than my small coil output.

As you can see this is clearly not 2400w. The coil should be kicking out up to 2 meter arcs! There is clearly something still not right so we went back to the workshop and kept thinking of what it could be.

Firstly, I rewired the capacitor bank again adding 2 more capacitors as it was slightly off. Then we had a realization. The current limiting magnetic shunts in the MOTs are lowering the power. We are using 6 MOTs as a charging choke so that means that there are 12 current limiters restricting the amount of current throughput in the coil.

 I spent most of yesterday hammering them out. It takes a long time and really put your tools through their paces but it should pay off. I even made my own tool by snapping a fork in half and using the handle as a chisel. If needs be I can even remove the limiters from the MOTs in the power supply but I will not do this yet as this might draw too much current and break the coil. 

As of now, this is where we are. I am going to test the coil loads tonight and if it works, the coil is officially complete. This blog will not be over though as we will keep making improvements and modifications to make it better. There will also be a proper video of it running. Wish us luck!

Next: The Coil Is Working!