The final bits.

Hi. This must be the last job on my Tesla Coil build. I need to make an earthing point on the main Tesla coil body. Most of the earth leads in my Tesla are connected to the earthing point on the neon transformer. These are

1. Connection to the strike rail underneath the primary coil perspex covering disc.
2. Connection to the lower terminal on the secondary coil.
3. Connection to the central rail on the Terry filter.

So I need to connect this point to my earthing plate on the conservatory wall. I could just run a wire from the earth plate through one of the vent holes in the Tesla base to the earth terminal on the neon transformer. The problem with this solution is that it would be impossible to remove this lead as the ring terminal needed on the end of the wire will not pass through the vent hole. Even if I enlarge the vent hole it would still involve removing one of the perspex walls of the base unit to attach/detach this wire.

After some thought I decided to fit an earthing point on the outside of the back perspex wall of the main Tesla unit. This would consist of 2 copper terminal lugs, one mounted inside, one mounted outside, connected through the perspex by a M6 bolt.

Above is the hardware for the terminal, I will probably replace the stainless M6 bolt with a homemade copper stud but will need to procure an M6 die first.

I made a small lead that finishes in a ring terminal to connect to the new earth point. I fitted the lead to give me a better idea where to site the hole for the terminal.

Marked up the point to drill the 6mm hole. I drilled the hole freehand, there were no obstructions and it was pretty easy to keep the drill at right angles to the perspex.

Result was a nice neat 6mm hole. My OCD placed it on the centre with the vent holes and level with the end of the neon transformer.

Here's the hardware fitted. I used 2 of the copper lugs from Alan at teslastuff.com. These are the best quality electrical lugs I have seen.

The terminal was connected to the short lead from the neon transformer earth point and the perspex sidewall replaced. Job done.

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More "Ground" Work on the Tesla Coil

Hi again. Over the last couple of days I have been working on the grounding system for my Tesla. As mentioned in my last post, I had already sank one copper rod in the lawn. Plan was to get another couple of rods form B+Q and have 3 ground points spread across the lawn. Slight problem, I sank the first rod several weeks back and I now can't find it!

So 3 rods were purchased from my local B+Q. The rods are about £12 each, they are 1m long 10mm diameter copper plated rod with a nice copper terminal clamp.

The 3 grounding wires will pass through the conservatory wall and meet in the pattress box. They will pass through 3 separate holes drilled with a super long 8mm masonry bit.

I removed a small piece of turf (about 18" square) and dug out some earth down to about 10". Here's a picture of the first hole. The wire will be sank under the turf by cutting a line with a spade and easing the turf up and pushing the wire under (a trick learned watching Virgin installation engineers).

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The copper plated rod was hammered into the centre of the hole. You have to fit the clamp onto the rod before you sink it as the hammering will splay out the top of the rod making it impossible to slide the clamp over afterwards. The grounding wire was attached using a solder ring terminal and the hole back filled and turf replaced.

Above you can see the position of the second ground wire. The process was repeated exactly the same as the first ground point.

And here is the 3rd and final ground wire laid out. All the wires run into the gravel filled trench that runs around the conservatory wall. You can see Karel (wife) covering the two completed grounds.

Here's the last rod being sank. Think I was pretty lucky that all the rods went in without to much trouble.

Here are all the 3 wires in place. Next job is to wire up the grounding plate in the conservatory wall.

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Grounding point for the Tesla Coil

I am going to need some way to ground my Tesla coil. Obviously dumping these high voltages into your household wiring isn't a good idea. I have heard of several other ways, one suggestion was to ground to your cold water pipes (thanks Mike), others include wire mesh lied flat on the floor etc. I wanted a neat and more permanent solution. I am going to install 3 copper grounding rods into my lawn. These four foot rods are available from B+Q, I have already sank one into the centre of the lawn, the other 2 will be close to the lawn edges as far from the central rod as possible. I have some really meaty 5 awg silicon coated wire which will run from the submerged tops of each rod, under the lawn to the wall of my conservatory.

The 3 wires will run under the drainage gravel around the edge of the conservatory and will run up the wall just to the right of the wall basket.

They will pass through the wall and come together in a single pattress box mounted in the conservatory wall.

The box will be sank into the wall just behind Milo to the left of the double plug socket. There is no existing house wiring to the left of the sockets, the mains wiring travels clockwise around the conservatory. I measured up and picked a drilling point on the outside wall which would bring me out central between the plug socket and the corner in the wall.

Drilled through with my super long 8mm masonry bit, slowing down and reducing pressure approaching breakthrough to prevent blasting a hole in the plasterboard.

I threaded a short piece of the 5 awg silicon wire through the hole just to check hole size was OK.

Here's the components for the earthing point, a 26mm deep single pattress box and a 100mm square 3mm thick copper plate. There will be some kind of terminal central in the copper plate, not decided on it's final design yet.

I masked up the plate and marked up the positions for screw holes to mount the plate to the back box. The 3.5mm holes were drilled and countersunk.

You can simply put the pattress box over the hole for the wire, draw round it and the remove the plaster. I used my Dremel with a spiral cutter, it made short work of the plaster, took about 60 seconds to work around the outline of the pattress. The cut out plaster can then be remove with an old flat bladed screwdriver or chisel.

I attached the copper plate to the pattress box and placed it into the cut-out. I am not going to permanently fit the back box yet. I will do it when I address the wiring to the 3 grounding rods.

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Bonding the Secondary coil acrylic end caps with Dichloromethane

Got lots of Tesla related stuff done this weekend. Firstly my little bottle of Dichloromethane turned up from from APCPure, a solvents seller on eBay. This meant I could glue (if that's what you call it) the toroid mount to the top cap of the secondary, and the small blanking plug to the bottom cap. I have never used Di-chlo before so was a little apprehensive. I knew if you get it anywhere else other than the bonding surfaces it marks your lovely clear acrylic. Anyway it went OK, I don't think I used quite enough as I ended up with air gaps but the bonds are absolutely solid.

Here's a shot of the toroid mount bonded in place, you can't really see the offending air gaps and the bond is good and completely seals the central hole used for mounting on the winding jig. Glueing the blanking plug to the base cap went much the same. A slight change of design here, I glued the blanking plug to the bottom of the end cap so it protrudes from the base of the secondary. I will adapt the Tesla base so the plug acts as a central locating pin into the primary mounting disc.

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Work on the Secondary Coil End Caps

I was hoping to finish off the top and bottom coil end caps today but this didn't work out. I needed to bond an acrylic plug into the central hole in the bottom cap. This is to close up the hole needed to mount the coil in the winding jig.

I also trial fitted the eight nylon bolts that will hold the coil down onto the Tesla body.

Here's a close-up of the plug in place. I also planned to bond the toroid mounting assembly to the top cap of the coil. This would, again, close up the hole needed for the winding jig.

Bonding was going to be achieved by using Tensol acrylic cement which a had purchased a while back from Trent Plastics. When I dug out the bottle the liquid was thicker than I had anticipated. From videos I had seen, bonding sheet acrylic was done using a water-like solvent that used capillary action to penetrate between two close fitting acrylic sheets. The liquid I had was like syrup and there was no way this would seep into a fine gap. I assumed all Tensol was the same and you know what they say about assumption. After a bit of investigating I think I have Tensol 12 which can be used for bonding gaps between rougher cut acrylic pieces. Tensol 70 is the version more suited for close fitting sheet acrylic but it was averaging out at £40 and minimum qty 500ml. Too much and too much. More homework was needed.

Here's what I found out. These water-like acrylic cements don't actually "glue" things together. It's more like a weld. The solvent dissolves the surfaces of the two pieces and the molecules merge from either side. The solvent evaporates and the two pieces become one. The solvent in these cements is Methylene Chloride also known as Dichloromethane. It's pretty nasty stuff but apparently it's all you need to bond close fitting acrylic and you can get it from eBay or Amazon. I paid £4.79 for 250ml, delivery was almost £8.00 because of it's hazardous nature. It should turn up tomorrow so will try it and let you know.

Anyway, crack on. I bought some shorter (12mm) cheese head slotted M4 nylon screws to fix the top and bottom caps in place. The 20mm bolts are a bit excessive!

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Secondary Coil Ground Terminal

I have just finished the lower electric connection to the secondary coil. As explained in previous posts this connection is made up of a 70mm x 23mm copper plate on the side of the secondary coil. The plate will be glued in place using 2 part epoxy. After deciding the final position of the copper plate I surrounded the area with masking tape, not really to offer any protection to the surrounding area, just as a guide. The inside of the area was deeply scored with sharp craft knife to produce a good key for the epoxy.

The copper plate was tinned (to aid soldering) and then the lower lose tail of the windings stripped of varnish and soldered to the copper plate. I used my new Dremel VersaTip to do the tinning and soldering. I bought it really to use as a small blow torch for tinning and delicate metal work, however I was very impressed with its soldering capabilities.

Here's a shot of the tail end of the windings attached to the copper terminal. The back of the plate was cleaned up with a brass wire wheel on the Dremel 8200 then cleaned with meths to remove all soldering residues. I removed the masking tape from around the scored hatchings on the coil, this would allow me to position the plate better by eye.
I mixed up a blob of 2 part 5 minute epoxy glue and applied it to the back of the copper terninal plate. Forgot to mention I had cross-hatched the back of the plate to aid bonding.

I positioned the plate onto the coil and lined it up parallel with the windings and made sure the lose tail was positioned nicely around the coil and taught. I held in position for about 5 mins while the epoxy hardened.

The plate got warm as the epoxy went off,  so easy to judge when it was safe to release pressure. I neatly positioned the tailing winding wire so it made a nice spiral from the end of the windings to the copper terminal.

Then I used a small brush to cover the tailing wire with insulating varnish which will protect and hold the wire in place on the form. I gave the tail wire 3 coats.

Here's the finished terminal. Think it looks pretty good.

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Winding the Secondary Coil for the second time.

The new secondary coil form has been sat in my homemade coil winder for long enough. It's time to start winding.

In my last post I gave the new stats for the replacement coil. The only change I have made is to start the windings 4.5cm from the base of the coil rather than 4.0cm. This change is just to allow a little extra room at the base of the coil to accomodate the copper plate that will act as the lower electrical connection. This will mean with the same number of turns (1050) the windings will finish 0.5cm higher, 8.3cm from the top of the coil.
 Before starting the winding I thoroughly cleaned the outside of the coil with meths to remove all traces of grease. I ran a line of masking tape around the coil with the top edge of the tape exactly 4.5cm from the base of the form. This would ensure that the windings would start exactly level with the base of the form. I measured 67.2cm (total height of windings required) from the top edge of the tape and marked this point on the form with a small pen dot. I would coil tightly up to this point then loose coil to the top of the form.
Well almost ready to start. Not quite. This time there's no help available..... and believe me, its better to have an extra pair of hands when winding a coil especially if you are relying on human resources to tension the feed wire and direct the winding wire onto the coil. Manual winding requires both hands, one to feed the wire (left in my case) and the other hand to push the coils together either with a non scratch implement or the back of your finger nail. This means you have no free hands if you need to stop (or start) the winding motor. My winding motor is powered by a variable power supply on the bench the winding jig, not exactly "to hand". I would need some way to switch it on/off remotely.
Bingo. Idea.

I plugged the power supply into one off those remote control mains switches. This one is a cheap as chips version from Maplin similar to the one linked.

Here's the little controller. I can either have it close to hand or even put it on the floor and press the off button with a press of a toe.

The winding wire end was clamped under the head of one of the white plastic bolts that holds the base coil end in place. You need to have a plan in place to clamp the wire end tight when you finish the windings, I decided to clamp it with the same method as the start, using one of the bolts that holds the top coil end in place.

Time to turn.

Well it took about an hour and went pretty well. Stopped just once when I realised I had left the door open. Two kittens and turning a tesla secondary coil are not compatible. Here's a quick vid of the finished coil. I have put on a couple of coats of insulating varnish. Still needs another couple of coats.

I am really happy with the finish. The varnish has a better finish than on my first coil. Next up is a few more coats and then fitting the copper plate electrical connection at the base of the coil.

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Secondary Coil Design and Begin

Today I started prepping for winding the new secondary coil. I have already worked out winding wire diameter and number of turns as explained in previous posts. I have chosen a design to work to with the help of Stefan Kluges excellent pages on producing the ultimate secondary coil, pages can be found at http://www.capturedlightning.org/hot-streamer/stk/tc/coilbld.htm.

The first job I had to do was to construct a rectangular copper plate that I will use as the bottom electrical contact to the secondary coil. It provides a very large area for electrical connection rather than just a small point of attachment. I thought it best to produce this plate first so I could confirm that the starting and finishing points for the winding were appropriate. I found a nice piece of copper sheet in my stock which was perfect.

These are the winding figures I planned to work to.

Length of turnings =1050*0.64

=67.2

Total form length =80cm

Windless portion =12.8cm

Windless portion bottom =4cm

Windless portion top =8.8cm

As you can see I have 4cm from the bottom of the coil form to the start of the windings. This is the gap that the copper plate will sit in. Here's the diagram from Stefan's page.

A good size for the plate was 70mm by 23mm so I masked up the piece of copper and marked up the dimension. Then, using a pair of 6" tin snips, I cut out the copper plate.

 The corners of the rectangle need to be rounded so I nipped them off with the tin snips and finished them off with a flat file.

The copper sheet was quite thin and so very easy to work. My coil form is already fitted on my coil winding jig. I placed a piece of masking tape 4cm from the base to represent where the windings would start. This helped me choose the initial dimensions of the copper plate.

This plate will eventually be bonded to the coil form using 2 part epoxy so it needed to be bent gently to match the curvature of the coil form.

Above is the finished plate in its approximate final position. Next job is to wind the coil. I am guessing that will be a 2 hour job so maybe I'll tackle that one evening next week.

One last thing. The kittens are driving me mad as they now use my Tesla coil as a shortcut from the settee to the living room door. So a trip to Bury Market to get some black vinyl material and a bit of trimming with scissors and we have the Tesla kitten guard.

Kitten Guard

Patent Pending

Didn't take long before its first test!!

Lulu

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A turn around the secondary coil. Again.

Hi everybody, not done a post for ages. Been busy with a bit of decorating and think I have not been looking forward to re-doing the secondary coil so have kept putting it off. I think it's time to finish the secondary so I can get on with testing and finally fire up this monster. Plus I think I need to move the Tesla to a safer area, at the moment it's in our freshly decorated living room which used to be pretty safe place where it wouldn't get damaged. Not anymore! Sadly we lost our old cat, Coco, a couple of months back but acquired 2 little rescue kittens, Milo and Lulu. They are mad. I haven't yet worked out if Perspex is claw proof and my Tesla looks like the worlds biggest scratching post.

If you want to see Milo and Lulu live take a gander at http://cats.damow.net from 10am till 4pm weekdays or anytime after 11pm any day. Live webcam of our kitchen (cats bedroom).

Anyway on with the Tesla. I have finalised the design for the windings on the secondary coil. The goal was to reduce the number of turns and this was achieved by increasing the diameter of the magnet wire on the secondary and reducing the length of the windings. I used JAVATC to generate the figures I needed.

With 1050 turns on the secondary resonance should be achieved by tapping the primary coil at turn number 11. The predicted resonant frequency is just over 180kHz and can be seen in the data below.

The new secondary coil blank is installed on my trusty winding jig. So glad I decided not to sell the jig on eBay after completing the first doomed secondary.

I made a small change to the winding jig. I replaced the original 148:1 motor/gearbox with a 50:1 unit. This should speed up the winding process, last time it took over 3 hours. The motor/gearbox units are produced by MFA and can be obtained from Maplin in a variety of ratios.

I have already purchased a few bottles of varnish to coat the coil after the windings are done. I am using the same as last time, it's made by a company called AEV (Advanced Electrical Varnishes) and is known as Ultimeg 2000/372 a high build Alkyd air drying anti-tracking varnish. The easiest place to get it is from Brocott on eBay but it's expensive in small amounts (£4.50 for 100ml plus p+p). You can also buy it from Hi-Wire Ltd for about £28 plus p+p but the smallest qty is 5 litres.

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