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LAN_403

|)4+80!|-|\\/

Tue Feb 06 2018, 12:08PM

Registered Member #61803 Joined: Thu Sept 21 2017, 09:18AM
Location: Bhopal,India
Posts: 34

profdc9 wrote ...

Here's an idea: get a red laser diode module and modulate that, and use a phototransistor to pick up the signal. Forget fiber optics, go free space! It will have to be aimed carefully, of course. I found the following on Amazon India:

Modulated Laser Diode

Photosensor

You might be able to adapt these for the interrupter signal. Go wireless!

Dan

Hmm... you surely are onto something...
I'll surely try this and let you know!!

|)4+80!|-|\\/

Tue Feb 06 2018, 12:19PM

Registered Member #61803 Joined: Thu Sept 21 2017, 09:18AM
Location: Bhopal,India
Posts: 34

So, can I use something like grounded rg174 coax with an optoisolator like 4n28??

teravolt

Tue Feb 06 2018, 08:36PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

yes, although I don't know what 4n28 configuration is or how fast. Open collector is probably what you want. but you must ground both ends of your coax in case of a strike. if you berry it in wet ground or copper pipe you will be better off. How much of your coil have you built, do you have pictures.

|)4+80!|-|\\/

Wed Feb 07 2018, 04:27AM

Registered Member #61803 Joined: Thu Sept 21 2017, 09:18AM
Location: Bhopal,India
Posts: 34

I've built the secondary , the inverter and the driver
A 4n28 is just an optocoupler
I don't understand how can I bury both ends of the coax to rf ground and have the signal transmitted??

profdc9

Thu Feb 08 2018, 05:02AM

Registered Member #58522 Joined: Tue Mar 15 2016, 08:33PM
Location:
Posts: 50

If you use the coax, you need to connect the outside of coax to a large capacitive body, like a metal chassis or a metal sheet as a counterpoise. The problem I think is that your Tesla coil is producing strong electric fields. The signal in a coax is carried on the center conductor and on the INSIDE surface of the shield. The electric field generates a high voltage on the OUTSIDE surface of the shield. At the ends of the coax, the inside and the outside of the shield meet, and the high voltage on the outside of the coax is connected to the circuit. You need to keep the high voltage outside of the circuit. The way this is usually done is to put the circuit into a metal box, and have a grounded coax connector with the outside conductor connected to the box. That way the box surface forms an extension (really a Faraday cage) that extends the outside of the coax shield. The inside of the coax is shielded by the closed volume of the coax shield + enclosure. You need to do this on both sides of the coax to prevent the fields of the Tesla coil from getting in, that is, both the interrupter and the Tesla coil driver need to be in metal boxes, and the coax connectors need to be grounded to their respective boxes, and ideally the metal boxes and coax connectors would be grounded to the chassis or a counterpoise or large capacitive body. An optoisolator sort of helps this, but the coax still acts as an antenna and a high potential will be present at the optoisolator that it will have to withstand.

This is going to be difficult to get working I think, but it could be done. I think it's better to use an optical link if possible, but there's no reason you could not get coax to work, assuming you are careful about shielding everything.

Dan

|)4+80!|-|\\/

Thu Feb 08 2018, 06:10AM

Registered Member #61803 Joined: Thu Sept 21 2017, 09:18AM
Location: Bhopal,India
Posts: 34

So, the chassis need to be grounded as well??
What ground should this be?
Rf ground or the driver''s ground?

profdc9

Thu Feb 08 2018, 03:31PM

Registered Member #58522 Joined: Tue Mar 15 2016, 08:33PM
Location:
Posts: 50

I think you need to join the ground of the circuit to the inside of the box. The coax connector should be something like this:

You drill a hole through the box and insert the coax connector through. On the inside of the box, you attach to the center conductor and the tab.

Joining the grounds at both sides may cause a ground loop. I would power the interrupter using a battery or an isolated transformer, for example, a wallwart with a transformer and a linear regulator in it. Also, you need to ground the case of the interrupter as well to a counterpoise or RF ground. If the interrupter is improperly grounded, touching the interrupter case might shock you! I don't think it will be easy to get all of this right.

Dan

|)4+80!|-|\\/

Fri Feb 09 2018, 08:59AM

Registered Member #61803 Joined: Thu Sept 21 2017, 09:18AM
Location: Bhopal,India
Posts: 34

So, how will the circuit work properly if I connect it's ground to rf ground??

teravolt

Mon Feb 12 2018, 05:43PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

a ground at the tesla and a safety ground at the interrupter just don't get struck while holding the interrupter

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