PopularFX
Home Help Search Login Register
Welcome,Guest. Please login or register.
2017-12-14, 02:16:38
News: A feature is available which provides a place all members can chat, either publicly or privately.
There is also a "Shout" feature on each page. Only available to members.

Pages: 1 2 3 4 [5] 6
Author Topic: Magnetic CARA - Proof of Concept  (Read 24327 times)

Hero Member
*****

Posts: 1219
Ok,  yes, automated switches would be great.  No i don't have any, but i can order some,   reed relays, 5V, 12V?
12V would be best.  Do you still have some CMOS gate chips (eg. from the CD4xxx series) that you used in the Dally project and some small Darlington transistors or mini MOSFETs ?
If you have some old computer modem cards you can cannibalize them for the little relays.


I have another bobbin which i can put some thicker wire on, is  AWG 23 enough or thicker? (i now have AWG 28 on).
I was thinking 2x the diameter of AWG28.
   

Hero Member
*****

Posts: 1181

DMMs and fingers are too slow :(

ok,  you mean something like this, see screenshot

Yellow is across the CSR (A-B)
Purple is across C1 (A-ground)
Blue is across CSR-C2 (A-C)
Green is current in L1 (B-L1) @ 1A/Div.

Using bottom half of the pot core only, so 11mH, 30V drain voltage, pulse set at 1ms (1KHz) on the FG.

Itsu
   

Hero Member
*****

Posts: 1181
12V would be best.  Do you still have some CMOS gate chips (eg. from the CD4xxx series) that you used in the Dally project and some small Darlington transistors or mini MOSFETs ?
If you have some old computer modem cards you can cannibalize them for the little relays.

I was thinking 2x the diameter of AWG28.

i do not recall using any cd4xxx chips in the Dally project, but i have some in my parts stock, also some mini MOSFET's
I found some little relays on old modem and router cards.
Awg 23 is almost twice the diameter of awg 28.

Itsu
   

Hero Member
*****

Posts: 1219
OK,  you mean something like this, see screenshot
Let's see:
At the beginning C1 had 30V across it and since C1 has capacity of 39.82uF and this represents 17919μJ according to E=½VC2
After the pulse the voltage in C1 has fallen to 23V which represents 10532μJ
Si the energy loss in the C1 is 10532μJ - 17919μJ  = -7387μJ

C2 (1.154uF) started at 0V and ended with 90V after the pulse which represents 4674μJ of energy gain. (mechanical energy gain is not counted here)

So the Out/In energy efficiency is 4674μJ / 7387μJ = 63%  ...which is pretty bad, but I think that we can get it above 90%.

   

Hero Member
*****

Posts: 1219
I do not recall using any cd4xxx chips in the Dally project, but i have some in my parts stock, also some mini MOSFET's
I found some little relays on old modem and router cards.
OK, so set up two relays to be driven by the Sync output of your signal generator via a miniMOSFET.  The SG outputs around 4V so this might not be enough to drive the MOSFET.  If this is the case use a small MOSFET driver or use a small Darlington BJT transistor instead.
Put a small flyback diode in series with a 47Ω resistor across each of the relay's coil.  All of these do not need to be high power components.

One relay will be acting as switch S0 and the second relay as switch S3 (the one that shorts C2) just like in my Falstad simulation.

I will PM you with the SG settings so people are not bored with stuff that is relevant only to your test gear.
   

Hero Member
*****

Posts: 1181
Let's see:
At the beginning C1 had 30V across it and since C1 has capacity of 39.82uF and this represents 17919μJ according to E=½VC2
After the pulse the voltage in C1 has fallen to 23V which represents 10532μJ
Si the energy loss in the C1 is 10532μJ - 17919μJ  = -7387μJ

C2 (1.154uF) started at 0V and ended with 90V after the pulse which represents 4674μJ of energy gain. (mechanical energy gain is not counted here)

So the Out/In energy efficiency is 4674μJ / 7387μJ = 63%  ...which is pretty bad, but I think that we can get it above 90%.




Ok,  good to know,  i wound a new coil, now with AWG23, it measures 80mH when clamped together and 2.6mH with upper half removed.
Using the same setup, here is the screenshot

Yellow is across the CSR (A-B)
Purple is across C1 (A-ground)
Blue is across CSR-C2 (A-C)
Green is current in L1 (B-L1) @ 2A/Div.!!!!

Using bottom half of the pot core only, so 2.6mH, 30V drain voltage, pulse set at 1ms (1KHz) on the FG.

Regards Itsu
   

Hero Member
*****

Posts: 1219
I wound a new coil, now with AWG23, it measures 80mH when clamped together and 2.6mH with upper half removed.
And what is the resistance of this coil?

Using the same setup, here is the screenshot

Yellow is across the CSR (A-B)
Purple is across C1 (A-ground)
Blue is across CSR-C2 (A-C)
Green is current in L1 (B-L1) @ 2A/Div.!!!!

Using bottom half of the pot core only, so 2.6mH, 30V drain voltage, pulse set at 1ms (1KHz) on the FG.
So this time the C1 voltage has fallen from 30V to 3.5V and the C2 voltage has risen from 0V to 140V, which represents energy changes -17675μJ and +11309μJ, respectively.  This works out to 63% Out/In ratio, ...again.
This is not surprising if the time constant for the L1 circuit is comparable with the pulse width and according to this we should be operating at much shorter pulse widths than this time constant when the current waveform is still a straight line.

   

Hero Member
*****

Posts: 1181
And what is the resistance of this coil?

Coil measures 1.5 Ohm.

Regards Itsu
   

Hero Member
*****

Posts: 1181
OK, so set up two relays to be driven by the Sync output of your signal generator via a miniMOSFET.  The SG outputs around 4V so this might not be enough to drive the MOSFET.  If this is the case use a small MOSFET driver or use a small Darlington BJT transistor instead.
Put a small flyback diode in series with a 47Ω resistor across each of the relay's coil.  All of these do not need to be high power components.

One relay will be acting as switch S0 and the second relay as switch S3 (the one that shorts C2) just like in my Falstad simulation.

I will PM you with the SG settings so people are not bored with stuff that is relevant only to your test gear.


Ok,  got it going, 1 relay with 2 separate contacts (make), one making S0, the other making S3 (shorting C2), see screenshot1

Yellow is MOSFET driver input (CH1)
Blue is the relay drive transistor collector
green is the current through L1 (500mA/Div.)

Screenshot 2 is expanded time base, same traces (current is 1A/Div.)


Regards Itsu
   

Hero Member
*****

Posts: 1219
Are you driving the transistor driving the relay coils from the CH2 Sync output on the front panel ?  Is this blue signal active when HIGH?
I am asking because if it is active when HIGH, then the the L1 driving pulse is occurring while the relay's coil is energized, which is wrong.
   

Hero Member
*****

Posts: 1181
Are you driving the transistor driving the relay coils from the CH2 Sync output on the front panel ?  Is this blue signal active when HIGH?
I am asking because if it is active when HIGH, then the the L1 driving pulse is occurring while the relay's coil is energized, which is wrong.

Sorry for being ambiguous, yes i am driving the transistor driving the relay coils from the CH2 Sync output on the front panel.
And no, this blue signal is not active when HIGH.

See new screenshot where i added the purple trace being the CH2 sync signal from FG.

Video here:  https://www.youtube.com/watch?v=1x0Pwl4kaaM&feature=youtu.be


Regards Itsu  
« Last Edit: 2015-02-21, 12:02:28 by Itsu »
   

Hero Member
*****

Posts: 1219
Do you know what is the delay between the deactivation of the relay's coil and the relay's points actually opening ?
This delay in my last relay was above 2ms and I am afraid that the relay's points might be closed so long, after the relay's coil is deenergized, that they are still closed when the L1 is pulsed by the Q1 MOSFET.

Also, did you measure the voltage between the collector and emitter (C-E) of the final BJT (bipolar junction transistor), that drives the relay's coil, to see whether this voltage exceeds the allowable E-C voltage in its datasheet.  If the voltage spike across C-E exceeds the maximum allowable C-E voltage rating of this transistor, then decrease the 47Ω resistor to avoid its damage.
Furthermore, you should not be driving the Bases of the push-pull BJT pair (de facto, a current amplifier with unity voltage-gain) directly from the signal generator without a resistor in series  >:-)  
Compare the maximum Base current in these transistors' datasheets and the maximum output current of your signal generator on its Sync output.

Finally, when you lift one of the core halves, you see a one cycle of a sine wave of L1C1 self-oscillation because the inductance of L1  decreases and this accelerates this self-oscillation so much that it can complete one full period of oscillation while the Q1 MOSFET is closed.  This does not happen because of core saturation.  Such saturation is manifested by the curving up of the current ramp and is easier to achieve when the core halves are clamped together.


P.S.
Quite a clunker you have built ;)  
Maybe it would be good to slow down the pulse repetition frequency (PRF) so your words on the video are not jammed by the clunking noise and the relay does not wear out quickly.
« Last Edit: 2015-02-22, 07:50:45 by verpies »
   

Hero Member
*****

Posts: 1181
Do you know what is the delay between the deactivation of the relay's coil and the relay's points actually opening ?
This delay in my last relay was above 2ms and I am afraid that the relay's points might be closed so long, after the relay's coil is deenergized, that they are still closed when the L1 is pulsed by the Q1 MOSFET.

The relay is an ALA2PF12  (5A), and it seems it takes 15ms to open or close  
So no adjustment is needed as there is 24ms between opening of the relay and activating of the MOSFET, see screenshot.

Quote
Also, did you measure the voltage between the collector and emitter (C-E) of the final BJT (bipolar junction transistor), that drives the relay's coil, to see whether this voltage exceeds the allowable E-C voltage in its datasheet.  If the voltage spike across C-E exceeds the maximum allowable C-E voltage rating of this transistor, then decrease the 47Ω resistor to avoid its damage.

The used transistor 2SD1266 can handle 60V C-E voltage according to its specs, and the blue trace shows that it never exceeds that, so looks OK to me.

Quote
Furthermore, you should not be driving the Bases of the push-pull BJT pair (de facto, a current amplifier with unity voltage-gain) directly from the signal generator without a resistor in series  >:-)  
Compare the maximum Base current in these transistors' datasheets and the maximum output current of your signal generator on its Sync output.

OK i will check on the resistor needed between the FG (CH2 sync) and the push-pull pair.

Quote
Finally, when you lift one of the core halves, you see a one cycle of a sine wave of L1C1 self-oscillation because the inductance of L1  decreases and this accelerates this self-oscillation so much that it can complete one full period of oscillation while the Q1 MOSFET is closed.  This does not happen because of core saturation.  Such saturation is manifested by the curving up of the current ramp and is easier to achieve when the core halves are clamped together.

Roger that, removing one half decreases the inductance, thus decreasing the chance of saturation.

Quote
P.S.
Quite a clunker you have built ;)  
Maybe it would be good to slow down the pulse repetition frequency (PRF) so your words on the video are not jammed by the clunking noise and the relay does not wear out quickly.

 ;D   Yes make a lot of noise, but i wanted to show you how with unchanged FG settings the thing behaves, i will play with the PRF to slow it down.


Thanks,  regards Itsu
« Last Edit: 2015-02-22, 13:46:45 by Itsu »
   

Hero Member
*****

Posts: 1219
The relay is an ALA2PF12  (5A), and it seems it takes 15ms to open or close  
That's excluding contact bounce time ;)
If you scope the current through the coil and the current through the relay's contacts, you might find a very different number.  (for this test it's best to supply the relay's contacts from a DC PS, or a battery, through a 10Ω CSR)

   

Hero Member
*****

Posts: 1181

I have increased the relay de-energize time from 25ms to 50ms just to be sure (CH1 burst delay time)

Then i measured "in circuit"; yellow is voltage across a 12 Ohm CSR resistor in the relay coil supply line, green is the current through the L1 coil.

We see the bouncing contacts when the relay closes and a clean cut off when the relay opens, then 50ms later the current through the L1 coil, see screenshot.

So the MOSFET switches correctly outside the C1 load / C2 discharge window.

I have added a 1 KOhm resistor in the FG CH2 sync / base of the push-pull relay driver line.

Regards Itsu

   

Hero Member
*****

Posts: 1219
OK, so now you have successfully automated the closing of the S0 and S3 switches by an electromechanical relay.

Now, we should hunt for the energy leaks with an immovable (clamped) core.
According to conventional Electronic Engineering, the energy recovery into C2 can can achieve 100% efficiency theoretically, and practically it can achieve >95%, as evidenced by the observed efficiencies of switching power supplies (operating in inverting buck-boost mode) that function on the same principle as the CARA circuit with clamped core, with the difference of C2 being in place of the load.

The obvious energy leaks are the resistances (including the RDS(ON) of the Q1 MOSFET) as well as the 0.9V voltage drop of  D1 and hysteresis losses of the core (which should be minimal for a ferrite core at these frequencies).
I'm open to suggestions where other energy leaks might be (e.g. this one)

I hope the major energy leak is not due to D1 because if it is then we will have to do synchronous rectification like some of the commercial buck-boost solutions (see here and here)


« Last Edit: 2015-02-25, 02:17:43 by verpies »
   

Hero Member
*****

Posts: 1181

I am not sure from who you expect these suggestions, but as i seem to be the only one around here i suspect you mean me.

Well, i did not even know we had energy leaks  :o, so the one mentioned by you are fine with me.

But i don't think we would get rid of them, i mean the Rds(on) of Q1 is 0.5 Ohm and we might improve that to 330mOhm with another MOSFET.
Or what about replacing also Q1 with a relay?

The 0.9V voltage drop of D1 is something we are stuck with, right?
What about the 0.1 Ohm csr?  We could get rid of that by using the current probe only.


Regards itsu
   

Hero Member
*****

Posts: 1219
I am not sure from who you expect these suggestions, but as i seem to be the only one around here i suspect you mean me.
No i was writing to the lurkers out there.

Well, i did not even know we had energy leaks  :o
Well if the recovery efficiency is only 63% then 37% is leaking out somewhere.

But i don't think we would get rid of them, i mean the Rds(on) of Q1 is 0.5 Ohm and we might improve that to 330mOhm with another MOSFET.
We could but I do not know if it is worth it.  I need to calculate the resistive losses first.
Could you scope the voltage waveform across D1 to see that the losses are there?

Or what about replacing also Q1 with a relay?
Too slow.  It would be feasible only with reed relays and a much larger (and slower) coil in multiple Henry range.

The 0.9V voltage drop of D1 is something we are stuck with, right?
No, we could try a silicon diode that has a voltage drop or get rid of the diode altogether and substitute it with synchronous rectifiers.

What about the 0.1 Ohm csr?  We could get rid of that by using the current probe only.
We don't really need it.  It is useful for probing only.
You can short it with copper wire for a while to see how much difference it makes in recovery efficiency.
   

Hero Member
*****

Posts: 1181
Quote
Could you scope the voltage waveform across D1 to see that the losses are there?


Ok,  see screenshot 1,  voltage across D1 (yellow) compared to current through L1 (green).


Screenshot 2 i did take yesterday and is the voltage across C1 (Blue), the voltage across C2 (yellow) and the current through L1 (green)
Back to 2 second PRF, 50ms delay after dropping the relay to activate the MOSFET.

Regards itsu
   

Hero Member
*****

Posts: 1181


Calculating the efficiency of C1 versus C2 from the above 2e screenshot data leads to 64.2%

C1 39.82uF @ 30V = 17919uJ
30 - 2.6 = 27.4V
C1 39.82uF @ 27.4V = 14947.6uJ
C1 lost 17919 -  14947.6 =  2971.4uJ
C2 1.154uF @ 57.6V = 1914.35uJ
Eff = 1914.35 / 2971.4 = 64.4%



After bypassing the csr i now calculate the efficiency from the data from the below screenshot as 69.7%   :)
 
C1 39.82uF @ 30V = 17919uJ
30 - 3.5 = 26.5V
C1 39.82uF @ 26.5V = 13981.8uJ
C1 lost 17919 - 13981 = 3938uJ
C2 1.154uF at 69V = 2747.1uJ
Eff = 2747.1 / 3938 = 69.7%


Regards itsu
   

Hero Member
*****

Posts: 1219
Yes that's an improvement, but I think that the largest energy leak is in D1

Look at the little red area that I marked on the scopeshot below.  The current should not be reversing through D1 at all.
The negative current excursion is a leak and a fuel for oscillations that follow it.

Also, the current through L1 should have much longer rising ramp than the falling ramp.  More like the proportions here.

P.S.
CH1 should not be inverted in your latest scopeshots because it creates a graphical illusion that C2 absolute voltage is decreasing while in fact the absolute voltage across C2 is increasing with time (albeit it's a negative voltage)
« Last Edit: 2015-02-24, 23:30:05 by verpies »
   

Hero Member
*****

Posts: 1181
Yes that's an improvement, but I think that the largest energy leak is in D1

Ok,  i checked out severall diodes for lowest forward voltage and this RU4D diode came out as lowest; 0.439V, together with a mica spacer  between the pot core halfs to create a "much longer rising ramp than the falling ramp" current through L1, i redid the efficiency tests which now came out at 89%, see screenshot 1 data
The pulse period was set at 1.369,863,0ms

C1 39.82uF @ 30V = 17919uJ
30V - 4V = 26V
C1 39.82uF @ 26V = 13459.2uJ
C1 lost 17919 - 13459.2 = 4459.8uJ

C2 1.154uF @ 83V = 3974.95uJ

Eff = 3974.95 / 4459.8 = 89%

The voltage across this RU4D and the current through L1 can be seen in screenshot 2

Quote
Look at the little red area that I marked on the scopeshot below.  The current should not be reversing through D1 at all.
The negative current excursion is a leak and a fuel for oscillations that follow it.

That ringing signal on the current (through L1, not D1) appears only when attaching the ground lead of the probe at the anode of
the diode when measuring the voltage across the diode.
It is NOT there when removing the probe, see screenshot 3

See screenshot 4 for comparing current through L1 (green) and D1 (purple)

Quote
Also, the current through L1 should have much longer rising ramp than the falling ramp.  More like the proportions here.

Ok, as mentioned, i had to add a mica spacer to get a similar current pattern like that.

Quote
P.S.
CH1 should not be inverted in your latest scopeshots because it creates a graphical illusion that C2 absolute voltage is decreasing while in fact the absolute voltage across C2 is increasing with time (albeit it's a negative voltage)

Ok,  done that at screenshot 1.

Regards itsu
« Last Edit: 2015-02-26, 07:48:33 by Itsu »
   

Hero Member
*****

Posts: 1219
Good independent work  O0

The scope probe at anode as the cause of ringing is good news.
I have to think about it, now.
   

Hero Member
*****

Posts: 1181

I used another larger Pot Core, a Siemens P7042 and a new coil:

0.4mm wire (AWG 26)
16.3mH @ 10Khz without ferrite
18.5 Ohm DC resistance

Screenshot:

yellow: voltage across C2
blue:    voltage across C1
green:  current through L1

Pulse period 10ms

Calculations:

C1 39.82uF @ 30V = 17919uJ
30V - 17.6 = 12.4V
C1 39.82uF @ 12.4V = 3061.36uJ
C1 lost 17919 - 3061.36 = 14857.64uJ

C2 1.154uF @ 158V = 14404.2uJ

Eff = 14404.2 / 14857.64 =  96.9%


Regards Itsu
   
Group: Elite
Hero Member
******

Posts: 3036
It's turtles all the way down
Good work guys, sorry I haven't been able to join in.

Right now I'm trying to write a sim for a free running version of CARA that will recycle the energy back into the supply capacitor, so that I can play with tuning and easily see the effects of tuning in real time operation

. When I get the basic idea finished, I will transfer the circuit to the real world variable inductance setup. (the sim doesn't allow for variable inductance)

It will be based on a flyback converter with spring loaded movable core materials operating at mechanical resonance.

I've been thinking this could also be attempted with a small amplifier feeding the core and a position sensor, pickup coil or accelerometer to provide positive feedback.

Such a method may have been used in the TPU, i.e. letting the coils sing or squeal at their acoustic resonant frequency with an acoustic feedback sensor of some type feeding the amplifier that drives the coils. So simple, no wonder we may have missed it.
This would surely explain the gyroscopic effect, especially if two frequencies were used in the filter.

Regards, ION


---------------------------
Just because it has a patent application or is patented does not always mean it really works.
   
Pages: 1 2 3 4 [5] 6
« previous next »


 

Home Help Search Login Register
Theme © PopularFX | Based on PFX Ideas! | Scripts from iScript4u 2017-12-14, 02:16:38