New Rosemary Ainslie Demonstration Scheduled for Sunday, 4 August 2013

[poynt99]

I'm somewhat disappointed that it appears they will be going with a 1 Ohm 5W rather than the "standard" 0.25 Ohm for the new CSR off the battery. This is insane, as my analysis indicates that with a 72V supply, 20% duty cycle, and full +/- gate drive, that 1 Ohm CSR is going to be dissipating an average of about 20W! Hope they've got a fire extinguisher on hand. LOL.

Also not good practice, is they will be shorting this new CSR when testing with the horrid original CSR array, but leaving it 'in_tact' for the remaining tests.

[MileHigh]

Poynt:

Those ceramic resistors get a nice internal red glow if I recall.  Like a hot coal, something that could burn a hole in your carpet and cause paper to ignite.  Meanwhile I think I read that Rosie wants to measure the resistance of the function generator by putting her probes across the FG leads, presumably when it's on?  That makes the multimeter very unhappy.

Also, these guys are nicely nuts!

http://www.youtube.com/user/Photonvids/videos

[poynt99]

Yes, those guys are nuts.

Imagine their 1 Ohm 5W CSR as this neon tester:
http://www.youtube.com/watch?v=AGXQNLq19FQ

[poynt99]

And btw,

If they had chosen instead to use the value I recommended, i.e. the 0.25 Ohm, it would only dissipate about 5W for the same settings. 

[TinselKoala]

I don't understand all this kerfluffle over the silly csrs. She has four perfectly usable non-inductive resistors that she can use. They are rated 1 ohm 25 Watt and are designed to be heatsink mounted easily. Two in parallel at the Batt neg post with a nice copper strap connecting them, and two in parallel at the present position on the board mounted as they are now, would make me perfectly happy. Nothing needed to be bought except for some copper strip or braid.
The "negative power product" will still be there as before, Poynt99's tests will still work as before, everything will be fine.



Here's another little puzzler for you all to consider.

Using the schematic below, the standard one but with the insertion of DC milliammeters as shown. Set the FG for DC output at whatever negative voltage that will give oscillations in Q2 and an indication of 120 mA on the meter mA1. (Or if you can't set DC output, set a short Q1 ON duty cycle and a gate drive of 0 V positive to keep Q1 off, and set whatever negative offset is necessary to make the oscillations and give the 120 mA1 reading.) For me with Little Bryan (one Q2) this is about -8.3 volts DC unloaded, of course clipped to about -4 volts when hooked to the circuit.

Now... What does mA2 read?

Next.... without changing anything on the FG... open the Switch. What do the ammeters mA1 and mA2 read?

Next.... without changing anything,  disconnect only the Drain of Q1. What do the ammeters read?

Compare, contrast, discuss.