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Bens foray into building a cap bank with uzzors charger

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vk2fro

Thu Jun 23 2011, 06:13PM

Registered Member #3930 Joined: Sun Jun 05 2011, 07:27PM
Location: Sydney, Australia
Posts: 33

Version 2.0 - heavier traces, board slightly reorganised, and parts labelled properly (2 ic's and a transistor).

Comments? :)

Once you all think its looking good, I'll head over to the "hackers space" (a workshop a few suburbs over) and knock up a board :)

edit: BUM! forgot to rename the fast diodes - they ARENT 1N4004's - theyre FR307 1000V diodes. The two zener's are 5 watt jobs. Can you tell I overspec my parts?? ;)

Forty

Thu Jun 23 2011, 07:00PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

as long as you've checked over the circuit a few times to make sure everything is correct, i'd say go for it.

vk2fro

Fri Jun 24 2011, 10:38PM

Registered Member #3930 Joined: Sun Jun 05 2011, 07:27PM
Location: Sydney, Australia
Posts: 33

Heres version 2.2; now I have all my parts. The solder pads for Vin and the transformer fit the PCB headers perfectly on the 1:1 printout, along with all my diodes once I changed them to the correct device size.

Note most of the 45Â° angle turns have now gone, and the board has even SHRUNK by 1Cm :) The very busy section up near the comparator has also been made less busy, which should make for less chance of getting a solder bridge / bum board from the fab place.

I have created gerbers and have studied the circuit to make sure nothing has been miswired. I'm going to get itstore to make the boards ($25 bux for 10 is cheepo!)

Now just have to A) wait for bank balance to have money in it, and B) wait for my darn caps and IRF540's to turn up (bloody ebay!)

Cheers
Ben

Forty

Sat Jun 25 2011, 12:15AM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

get a few more posts (site rules) and you can likely sell some of your extra boards on here to make some money back.

vk2fro

Sat Jun 25 2011, 11:26AM

Registered Member #3930 Joined: Sun Jun 05 2011, 07:27PM
Location: Sydney, Australia
Posts: 33

Good thinking - I can probably sell them as kits, with the PCB, major components, and leave the variable components (voltage divider resistors, resonance cap) up to the builder (as these components vary).

The majority of people will only want one voltage, but thats easily settled, omit one voltage divider resistor and replace the switch with a wire link.

I have just added metering - the cheap LED 200V DC meters on ebay will do the trick- even stuffed an LM7805 on board to power it :) By changing the sense resistor on the board, a variety of voltages can be obtained from the Meter In pad on the pcb. Right now I have a 0-200v meter on the way, so I set the resistor to divide input voltage by 10. This will give a reading of 90 volts at 900volts across the bank. First thing I will do is snip the anode lead of the decimal point on the meter ;) They have a ground that is common with the input (measured) voltage, so only need 3 connections.

I considered powering the meter from the cap bank charge, but at 900 volts, the zener would be small, but the pass resistor would be a huge 50watt job. It would have been nice though, the meter would display voltage in the bank, even with the power off, as such, doubling as a "bank has charge" indicator.

This thing is probably going to go through a few revisions before its time to have the boards made - major changes to 3.0 include fixing the mosfets vertically, addition of metering output. Also pad spacing between I/O's allows for the use of the nice PCB mount screw terminal connectors jaycar sells (they appear to fit nice on the 1:1 printout anyway :P)

Heres version 3.0.

Forty

Sat Jun 25 2011, 05:21PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

you can get those terminal connectors on bgmicro for a lot cheaper. although i don't know about shipping costs to australia.

vk2fro

Sat Jun 25 2011, 06:10PM

Registered Member #3930 Joined: Sun Jun 05 2011, 07:27PM
Location: Sydney, Australia
Posts: 33

hehe too late - already got em - and yeah shipping - probably get them 3 weeks later - got mine from jaycar in one day. :)

vk2fro

Mon Jun 27 2011, 06:32AM

Registered Member #3930 Joined: Sun Jun 05 2011, 07:27PM
Location: Sydney, Australia
Posts: 33

Drat - cant add an attachment to my previous post or I would have edited it instead of double posting.

Look what turned up today

1309155963 3930 FT117994 Img 20110627 162014

Sitting on top in the forground is a PC psu cap - these things are huge. Each is rated at 2.4mF 450b (525 surge), which nets me a bank of 24mF at 450V or 12mF at 900V :)

I will start by adding a rotary switch to my charger, and setting it up for 80,160,320 and 450, and reform these before banking them up - will do them one at a time. For lower voltages (12 v) I have 4 7ah gel batteries. I'll just tack one on after the other in series to get to ~ 50 v

of course when I can afford it I'll be buying another 30 caps, along with an ESR meter so I can check them all, and arrange them in two parrallel strings of 20, for a whopping total of 10kJ ish :)

vk2fro

Thu Jul 14 2011, 05:21AM

Registered Member #3930 Joined: Sun Jun 05 2011, 07:27PM
Location: Sydney, Australia
Posts: 33

Since I cant attach another pic to my previous post, I apologise for triple posting.

Heres my final revision of the cap charger board in the flesh!

Observant viewers will notice the fast diodes are missing. They're too big for the boards holes. Since I dont have a 0.8mm mini drill, I will need to wait until I get one to finish adding the diodes.

As I STILL havent found a busted TV to rip the flyback out of, testing cant go ahead at the moment anyway.

If all works well, I might offer the other 7 boards (I'm keeping 3) as a kit with all components included in the buy sell section, provided my post count is high enough as mentioned earlier. You just need to supply the flyback transformer and a 12V power source.

Forty

Fri Jul 15 2011, 01:17AM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

looks very nice.
I can't believe you could design and make that, but don't have an extra flyback transformer, lol.
I don't think it technically has to be a flyback core, any ferrite core should do, given that you can fit your windings in it.

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