Threadjacking is generally frowned upon in most forums, especially this one. If you have a related question, but it isn't completely pertinent to the question asked by the Original Poster, please start your own thread....
For the threadjackers out there, if you try to hijack a thread, and i see it, I will award you a Yosemite Sam Award...
While a Tesla coil is being operated, it often produces high-frequency voltage spikes on the NST side of the tank circuit, especially if an arc from the topload strikes the primary coil. These spikes can be extremely harmful to your transformer and to the mains supply, so it is very important to have some sort of low pass filter to suppress them.
One of the most common filters nowadays is the "Terry Filter," designed by Terry Fritz--an experienced Tesla coil builder. They use several high-voltage capacitors and resistors to shunt the voltage spikes to ground through an extra spark gap, and to decouple the NST from the rest of the circuit.
Unfortunately, all the parts that one would need to build this may get relatively expensive, and since this is a low-budget Tesla coil, the Terry Filter is not much of an option.
Another possibility would be to just have the extra spark gap, or safety gap. If your transformer is center-tapped, as many NSTs are, you would need
The spark gap is probably the simplest part of a Tesla coil. The gap acts as a high-voltage switch that releases the energy stored in the capacitor through the primary coil at just the right time.
There are several types of spark gaps. There is the single static gap, there is the multiple static gap, and there is the rotary spark gap (synchronous or asynchronous).
The single static gap can be as simple as two bolts facing each other with a space between them. It is important that the bolts are not pointed because sharp edges can lead to corona discharge, which means loss of stored energy. This type of gap is generally suitable for most coils. However, the electrodes must be kept cool in order for the gap to fire at the correct time. If they heat up, resistance decreases and the gap can fire at a higher rate, greatly affecting the output of the Tesla coil. The gap may be cooled by moving air across the contacts, or I have also seen magnets used. Any method of extinguishing
In order for a Tesla coil to operate correctly, the tank capacitor must be matched to the transformer. An online calculator is a useful method to calculate the correct capacitance. According to this calculator, my 9kV neon sign transformer requires a 0.0176uF capacitor (17.6nF).
To find the voltage rating of the capacitor, multiply the rated output of your transformer (in my case, 9000 volts) by 1.4 to get the peak voltage. 9000 x 1.4=12,600 volts. I'll round that to 13000 for a little extra safety. Since the capacitor in a Tesla coil is often charged to twice the transformer voltage, you must now double the peak voltage of your transformer. 13,000 x 2=26,000 volts for the capacitor. So, for my transformer, I will need a 26,000v, 17.6nF capacitor.
There are a few options for tank capacitor of a Tesla coil. The first is a single, large high-voltage pulse capacitor. Though they may be effective and not take up too much space, they tend to be rather expensive. They also MUST
Finding a transformer is always the best place to start when building a Tesla coil. The rest of the coil is based on the ratings of the transformer that you choose.
The high-voltage transformer I hope to use with this Tesla coil is the 9000 volt, 60 milliamp neon sign transformer shown below:
Tesla Coil 001.jpg Tesla Coil 002.jpg
Though neon sign transformers are the most commonly used for Tesla coils, other transformers such as oil burner ignition transformers (OBITs) or microwave oven transformers (MOTs) have also been used.
Since this Tesla coil is designed for a builder with a low budget, and the transformer is often rather expensive, I had to do some real digging. My neon sign transformer came from a local neon sign shop. The owner generously gave me two old neon sign transformers--the 9kV, 60mA shown in the pictures, and a 12kV, 30mA that I may use for another project. If you do not have a generous neon sign shop owner near you, OBITs and MOTs
This blog details my journey into battery backup for small micro controller based RF connected sensor nodes.
It is worth noting that much of what is written about battery charging is by the RC people. Their use model is quite different then that of battery backup.Definition: C: battery capacity in mAh.
Charge Rate is expressed as C/x.
If one chooses to charge at 100mA or less the cost is quite low. Add an additional dollar if you want to charge at rates up to 1.5A. The assumption is that the application uses a micro controller and you have 1 analog and 1 or 2 digital IO pins free. $0.46 LM317 (100 mA)
$0.19 1N5404 (a lower current device perhaps)
Total under $1.00Feb 14
The circuit I started with is was found at Fig3 and is a typical use of the LM317 to regulate current.
Building the wings is rather daunting, there are so many pieces to put together and they all must be accurate. The joining of the wings also needs to be very strong and secure, but I think I've done it pretty well
Over the Christmas period I got to do some more on my plane. I started on the wings.
I'll start by saying, I've been using PC's and their direct desktop ancestors since about 1980 or so, and have used CP/M, DOS, OS/2, just about every version of Window$ (including Windows 3.0, and the Win95 "desktop" known as "Bob"), Unix, and Linux.I've helped people do some configuration and network setup on Vista and Win7, although i do not own (and do not want to own) copies of Vista and Win7. I have been doing this for a while... I used to run a BBS 24/7 before there was such a thing as the internet. How i actually got any work done "back in the day" with 64k of memory and a pair of 180k floppy drives and a 1Mhz 8 bit processor is beyond me, but i did manage to get a few things done i guess.... So we'll skip most of the history lesson, and fast forward to a couple of years ago. At that time almost all of the computers in the house were running WinXP, and because i was tired of kicking my children off of my computer so i could so some web browsing or amp
Some more progress