Rosemary Ainslie COP>17 Circuit / A First Application on a Hot Water Cylinder

[Rosemary Ainslie]

Rose,

The 555 is a timer or oscillator. The switch is the MOSFET or IGBT.

If what you are describing about the "altering frequency and duty cycle" is in fact the quasi-stable state the 555 can go into under the right operating conditions, and you are not able to achieve this, then I would suggest that your group try a number of different manufacturers of the 555 itself. I found the variations were quite evident, and for me, only one type produced the desired quasi-stable state.

One other factor possibly influencing this "effect" is the proximity between the 555 and the switch. Yet another, is the switch itself. Are you using the IRFPG50? If not, that might be a place to start.

.99

Hi Poynty.     Where did you get all this license to comment?  Are you on probation?  Or was that a self-appointed exile?  In any event - I don't suppose it's my business.  Just really curious. 

I thought the switch switched the transistor?  How then does one refer to the 555 switching circuit?   And yes we're using an IRFPG50. 

Poynty - how does proximty to the MOSFET change things?  And should they be further apart or nearer?  I've got pictures of this on a previous post.  I'll try and find them.

Regards,
Rosemary

[poynt99]

I thought the switch switched the transistor?  How then does one refer to the 555 switching circuit?

The 555 circuitry is an oscillator/timer (not a switch) that drives (turns on and off) the switch, the switch itself being the MOSFET or IGBT.

And yes we're using an IRFPG50.

That is the best approach if you want to achieve the quasi-stable mode of oscillation in the 555. The IRFPG50 has a relatively high inter-electrode capacitance, and this "enhances" disruptive feedback to the 555 through the Gate lead. 

Poynty - how does proximty to the MOSFET change things?  And should they be further apart or nearer?

Proximity of the 555 circuitry and associated wiring to the MOSFET and Resistive load can have a great effect on the stability of the 555 operation. The distance not only has an effect, but the actual orientation of all relative to one another, especially the 555's orientation and distance to the load and/or switch.

Electromagnetic Interference (EMI) increases greatly with frequency (or rise/fall times) and current. This setup can emit large amounts of EMI, especially if running above 100kHz, but the transients alone will wreak havoc on unshielded circuitry, such as your 555 oscillator. Running at only 2.4 kHz can still cause disruptive interference to the 555 due to high dV/dt.

If you want to de-stabilize the 555 oscillator, try moving the load resistor closer to it, and vary it's orientation also. MOSFET proximity will probably have a lesser effect with regards to EMI and orientation, but it is still present.

.99

(PS. Stefan has given me full membership once again.)

[Rosemary Ainslie]

The 555 circuitry is an oscillator/timer (not a switch) that drives (turns on and off) the switch, the switch itself being the MOSFET or IGBT.

Get it.  The 555 drives the switch.  I should have known this.  I've written it in both papers.  Thanks Ponty.

Proximity of the 555 circuitry and associated wiring to the MOSFET and Resistive load can have a great effect on the stability of the 555 operation. The distance not only has an effect, but the actual orientation of all relative to one another, especially the 555's orientation and distance to the load and/or switch.

What is 'too close'?  What's the optimal distance required between the FET and the driver?  Glen had them on the same board - and Groundloop had them both on the same board.  We've done the same here - twice - with very little difference, if any, in the configuration to Glen's set up.

Electromagnetic Interference (EMI) increases greatly with frequency (or rise/fall times) and current. This setup can emit large amounts of EMI, especially if running above 100kHz, but the transients alone will wreak havoc on unshielded circuitry, such as your 555 oscillator. Running at only 2.4 kHz can still cause disruptive interference to the 555 due to high dV/dt.

With respect - I'm not sure what you're saying here.  What 'set up'?  The switch?  The MOSFET?  What needs shielding?  There is NO WAY that our inductor is causing electromagnetic interference.  It is entirely impossible - in the circuit tested - to get a stable relationship between the duty cycle and the frequency variations that we want to test.  And at this stage we're testing the set up without any inductive load connected.  Just testing the basic efficiency of the actual switch and it's 'driver'?  In any event - the 555. 

Poynty - I have an interminable quarrel with all you guys.  It's in the way you bandy words, terms and acronyms around without giving a clear indication of their meaning.  It hardly advances anyone's understanding.  PLEASE - even if it's as a courtesy to my lack of training - just explain things clearly.  No slick technical references PLEASE.  Just plain simple english.  Science is already hopelessly confused.  Lets keep it simple.   Even that 'high dV/dt' - gets me down.  I know what it means.  It's just - surely, so much easier to say extreme changes in voltage over time - or if you want to be more technical say - incrementally large changes in voltage over time.  There are MANY readers who, like me, have NO TRAINING.  And simple english at least advances some understanding.  This is not, after all, a purely technical forum for trained experts.  And I really would prefer it that we can all understand posts. 

If you want to de-stabilize the 555 oscillator, try moving the load resistor closer to it, and vary it's orientation also. MOSFET proximity will probably have a lesser effect with regards to EMI and orientation, but it is still present.

Again.  Why would I want to destablise the oscillator?  Is this required?  Our concern is that it's unstable.  We're trying to stabilise it.   

Kindest regards,
Rosemary

(DELIGHTED to read that you're re-instated BTW - and more so as you're engaging here.  Much appreciated)   

[Rosemary Ainslie]

Guys just a brief update on a small experiment that we're putting together.  Think of the polygonal 'patches' on a rugby ball - not sure yet whether they're to be penagons or hexagons  or some combination ? then extend the shape to the centre of a sphere - in a roughly conical construct but with flat sides - reaching to a point at the end.  Then add a small curve to the surface of the polygon.  Enough of them and we'll have a sphere. 

Then.  These are to be cut out of neodymium magnets - cylindrical - with the norths at the centre and the souths on the surface or vice versa.  That way we'll have a rough equivalent of a magnetic monopole.  Then.  Add pin bearings to each side - on a stand - and the hope is that it'll generate a spin at 180 degrees to the Earth's magnetic lines of force.  IF it spins then we unquestionably will have a generator if it's placed within a copper coil.

In any event I'm digging deep into the pockets to get this construct together - and, hopefully soon, I'll be able to report on it's success or failure.  I'm hoping for some kind of result by the weekend or soon thereafter.  We'll see.

By the way - it can't be patented as the construct has been made very public, by me, on a couple of forums already - including this.  And - if it does spin then it will answer some very deep questions - I think - especially as it relates to a magnetic field.

Regards,
Rosemary

We'll also be constructing some kind of plastic sphere to encase these in as there will be some considerable forces of replusion.

[IotaYodi]

Sounds a little like a buckyball. About the same configuration they used in the atomic bomb for implosion. Might be a little hard to construct. Got me to thinking if the magnets should be manufactured in the same latitude as the experimental sphere though it probably wouldnt matter.
Ive had a similar idea but using 2 interlocked toroid shapes with one vertical for the magnetic field and the other horizontal for the electric field. Iron would be the magnetic field toroid and a copper winding on the other toroid for the electric field. Maybe a resonant tuning on the coil. Orientation to the earths axis may come into play.  Just a wild idea.
Hope You build this sphere I would like to see it.