Buck converter for small wind turbine project

[rossw]

It looks hot and scary that top trace.

I don't think I ever saw anything quite like that before.

Looks to me like a fair whack of AC on there. The CRO has been in AUTO trigger and it's a bunch of sweeps superimposed.

[Burnit0017]

Hi, I have been trying to find material on how to use the scope. The channel grounds are the same points and all the channel grounds are the same as chassis ground. It is the only way I could get the sweep to show on the display.

When I try to measure the circuit using a DC channel mode the power supply over current protect feature on the bench power supply  kicks in and the power supply shuts down. What is the correct way to use the scope? It is a Tektronixs 2246. Any help will be greatly appreciated.

[Wolvenar]

Not sure if this helps but.

http://aries.ucsd.edu/najmabadi/CLASS/COMMON/XYZ-Scope.pdf

[Burnit0017]

Hi, thank you. I have reviewed the material. The only thing I can think of is the ground of the scope is at a different potential than the ground of the power supply. I have one scope that lost the trace during testing and I am not sure if it was because of age and just happen to stop working at the same time I was testing the circuit or the testing of the circuit was the cause for failure. I am trying  to avoid having a repeat of scope failure. Should I connect the scope chassis ground to the power supply chassis ground? Comments welcome

on page 45 it says the scope should have the same ground as the circuit being tested.
Is that the power supply chassis ground or the -V of the power supply? The power supply has three terminals, V+,chassis ground, and V-, maybe I am connecting the power supply wrong.   

[Burnit0017]

photo of power supply

[rossw]

Hard to tell from the pictures.
Take your multimeter.
Disconnect outputs from your power supply. Set it for about 10V.
Measure from + to - and tell us if it's 10V or 20V.
Measure from gnd (earth, the centre banana socket) to + and -.
Is there any voltage from ground to either? If so, how much?

If it's as I *SUSPECT* it is, you'll have 10V + to -, and nothing gnd to + or -.
If thats the case, you should jumper gnd to - in this case.
(Many of these power supplies had a solid jumper link installed between the banana sockets)

Now take your multimeter. Make sure the CRO and power supply are plugged in the same outlet.
Measure from power supply gnd/- to CRO ground. There should be no voltage.
Check from power supply + to CRO ground. There should be 10V.
Check ohms from gnd/- of the power supply to CRO probe ground. Should be under an ohm.

If that's all as indicated above, then you have a "normal" setup.
You CRO probes ground can go to the "ground" (0V) part of your circuit *ONLY*

If you're in doubt, you can connect a 10R in series with the cro probe ground to wherever you intended to put it.
10 ohms won't make any difference to the CRO readings - which should have a minimum input impeadance of 1M, and probably 10M. But if you try to "earth" to something that's 12V or more away, your 10R will smoke rather than the CRO.

(I once installed such 10R resistors in the little ground wire from the probe, when students kept blowing sh!t up)

[Burnit0017]

Hi, I found a manual for the power supply on line.

http://cp.literature.agilent.com/litweb/pdf/06284-90002.pdf


It has rear panel jumpers. I have to review the manual to determine what is the correct way to set the jumpers up. I did some measurements as instructed and found

Measurements from front panel, set for 10 volt output:

+ to - (10 volts)
+ to Gnd (0volts)
Gnd to - (-10volts)

It looks like the real panel jumpers affect the output of the front terminals.

Not sure how to set up jumpers on the rear panel, if anyone has experience with this type of power supply comments are welcome

[Burnit0017]

Hi, project update, thank you rossw, the power supplies are back on track.

[Burnit0017]

Hi, the power supplies have new rear panel terminal configuration. I am unable to increase the voltage at Vin of the buck converter.  I may still have rear panel connections mis-wired.

The top wave form is Vin of IR2117 and the bottom is Vs after mosfet.

I still have to add the fast recovery diode, it should be here in a few days.

The wave form at Vs shows the mosfet is turning on and off.   Comments are welcome.

[Burnit0017]

Hi, I managed to resolve most of the problems with the proto circuit when using the bench power supplies.  They were mainly caused from the power supplies and I had the new oscilloscope probes set to x10.

I still have to resolve one problem. The output from the 555 oscillator has a severe ringing that is transferred to Vs of the mosfet.  But the boot strap appears to be working with the Vs from the IR2117 connected to Vs of the mosfet and the mosfet is turning on and off.

[Burnit0017]

Hi, video shows manual operation of PMA and buck converter to a resistive load.
The mosfet is turning on during the off cycle of the IR2117. Is there a solution to this problem???  Comments welcome.

[Burnit0017]

Hi,
I found a reference to the problem on page 8 and 9.

 http://www.nalanda.nitc.ac.in/industry/appnotes/IR/ASSETS/TECHDOCS/APPNOTES/An978.pdf

It recommends increasing the boot strap capacitor to a valve greater than 0.47 uf. I will post results when available. 

[Burnit0017]

Greetings, I added the larger caps to the boot strap and the ringing is still there but only noticeable at lower RPM’s.

I am still using the 555 timer. I increased the duty cycle to 80% and inverted the output so the duty cycle at the input of the IR2117 is 20% high. I connect a 12 volt 50 watt light and spinning the PMA manually I was able to illuminate the 50 watt light with relative ease. Wow, a shorter duty cycle made all the different. The PMA was much easier to spin and even maintained momentum for a short period when I stopped spinning the PMA.

Without the buck converter I was unable to illuminate the 50 watt load under manual operation. 

I am still using the bench power supply to power the IC’s.

Performance has definitely improved.

I still need away to control the duty cycle at different PMA RPM’s and find away to power the IC’s from the battery or PMA. Next step is to try charging the battery. It maybe time to start thinking about adding a micro controller. Thank you for all the suggestions.     

[boB]

Greetings, I added the larger caps to the boot strap and the ringing is still there but only noticeable at lower RPM’s.

I am still using the 555 timer. I increased the duty cycle to 80% and inverted the output so the duty cycle at the input of the IR2117 is 20% high. I connect a 12 volt 50 watt light and spinning the PMA manually I was able to illuminate the 50 watt light with relative ease. Wow, a shorter duty cycle made all the different. The PMA was much easier to spin and even maintained momentum for a short period when I stopped spinning the PMA.

Without the buck converter I was unable to illuminate the 50 watt load under manual operation. 

I am still using the bench power supply to power the IC’s.

Performance has definitely improved.

Hopefully, performance will improve ever time you play with this stuff.  Expect to
blow it up from time to time while fooling with it though.

So, is the light changing brightness from you changing rotation speed ?  It doesn't look
like the duty cycle is changing there but the voltage is changing.   How about changing
the duty cycle and keeping the rotation constant with a motor or something ??
That's a cool thing to see working too.

I still need away to control the duty cycle at different PMA RPM’s and find away to power the IC’s from the battery or PMA. Next step is to try charging the battery. It maybe time to start thinking about adding a micro controller. Thank you for all the suggestions.   

[Burnit0017]

Hi, The pulsing from the light is caused from manual method I am using to the spinning the turbine. It does not allow for continues rotation, I am forced to release the belt drive pulley after a half a revolution, but it does increase the RPM to illuminate the 50 watt load. I am searching for away to supply power to the IC’s from the battery bank or from Vin.

This turning into a real learning experience. Getting the Mosfet to turn on and off  with a resistive load  is just the first part of the project, the circuit does not operate using a battery for a load at this time.

Using a shorter duty cycle does require less torque to spin the PMA. I am still trying to understand the MPPT algorithm. 
I am searching for a circuit that will adjust the duty cycle as the RPM increases.

Comments welcome.