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Bens foray into building a cap bank with uzzors charger

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vk2fro

Fri Jul 15 2011, 02:37AM

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

I'm surprised too - usually I have 1 or two flyback transformers hanging around. I will have a couple of transformers next week so all is good (some busted TV's to rip into)

edit:

I'm still working on this folks. I have 2 TVs now to gut the EHT transformers out of, for their cores, just waiting on some other components to arrive.

I have selected a 200 watt 10K ohm discharge resistor. Now just need to find a nice big contactor to switch it in when the switch on the control box is dialed to "dump" :)

The resistor should dump the bank in 5 minutes. A circuit will keep power from the 12V source to the led meter until the bank is below 12V, so its basically "while that meter is lit, stay away" :)

Edit:
A week or so later and television number one has been delivered, and has had its mainboard stripped from it. Amoungst other nice parts, I have one intact flyback. A second TV will be on its way in a few days. First edit was meant to mention "I have 2 TV's to gut being delivered by friends". One has turned up :)

All thats left to do with the telly is neck the tube and toss it into the bin.

Waiting for: Copper, SCR Clamp (on its way), plexi box, and a bigger control console box :P

vk2fro

Sat Oct 01 2011, 06:56AM

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

Well folks, progress!

I've found a local company who can make up my bus bars. I've also found a silicon chip article that entails a cap reformer circuit which is intelligent (uses a pic micro) and probably a good idea as I dont know the history of my caps, and dont want one to go boom near me.

I'll put the cap reformer kit inside a large plastic toolbox, which will also house the cap under test, and sit it outside. Since it runs off 12v, I'll pop a car battery nearby to power it.

My SCR has arrived, along with its clamp and a shedload of other bits and pieces.

I still need to order my bus bars, wind my transformer (I got the core out of a flyback today using a pair of needlenose pliers to remove the clip, and zippo cigarette lighter fluid to dissolve the glue. A AAA battery makes a great plunger to push the core out of the FBT :) I have some 3M acetate overhead projctor transparancy to use as insulation between the secondary windings. (conveniently pinched by a friend from his work LOL)

I also got some nice switches for the control panel, and a nice sloping panel box for the control cabinet that has one little problem! TOO SMALL *doh!* It'll get used for another project though, so I have to go back to RS components and order its bigger brother. (the box is not deep enough for my switches). I also got a 200 watt (!) 10K aluminium clad resistor. Its as big as a sausage roll! It will be my "dump" resistor should I choose not to fire the bank.

TO DO:
1. Order a freewheeling diode of ebay (big bugger)
2. Finish adding the components to the PCB (on their way from ebay)
3. Wind the transformer, replace globes in press buttons with LEDs
4. Build the control console
5. Build the SC cap reformer and reform my caps
6. Build cap bank box, order bus bar, attach caps to bar
7. Reform 11 more caps and add them to the bank.

7 will come later when I have spare funds to buy the extra caps. They will bring the bank total power to 5kj, which should be MORE than enough for a home version of the geek groups "Thumper" :)

Forty

Sun Oct 02 2011, 10:34PM

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

I haven't looked around on ebay yet for diodes, so i'm not sure if this will help, but I did find this:

vk2fro

Tue Oct 11 2011, 05:12AM

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

Thanks forty - that looks the business and cheaper than stuff I've seen on ebay (I dont really need a puck diode).

Might order 2 of them. My fast diodes turned up so I have fitted them to the PCB. All I am waiting on now is the 110K resistors (got 3000 assorted resistors from ebay) and a 5K trimpot.

The circuit will function without them, they are only the meter output, but I'd rather have the board finished ready for installation.

I also need to find a vibratory horn (for the firing alarm)

I also need to get off me bum and wind the step up transformer :)

vk2fro

Fri Oct 21 2011, 02:18AM

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

Hi guys

Further updates. I've ordered copper bus bar for my caps, along with a larger sloping panel box so I can get the control panel built.

I need some suggestion for the IO socket. It will carry low current (tops 300ma) at 12V to power relays in the cap bank box, for charging, bleeding, firing, and disconnection of the charger from the bank. I assume an 8 pin din will be suitable for this task? The incoming 12V will be fused with a 1A fuse, the max the control box will draw is 600ma, thats with the three illuminated switches lit, and the display, along with the trigger handpiece button (spectator control) lit. This is an impossible situation, as the charge light will immediatly go out once the selector switch is moved from charge to fire. Likewise, the remote and bleed/fire lights go out when the selector switch is moved to "charge".

So is an 8pin din suitable for this purpose. The bank will have its own inbuilt SLA batteries, and a key that needs to be inserted to power the box. (a shorted 30A pair of andersons).

Without the control box connected, the bank box will be in a state of no charge, no fire, bleed resistor connected. This is with or without the "arming" anderson key inserted.

As well, a 4 pin (as found on CB radios) microphone socket and plug will interconnect the trigger remote to the control box, and a bnc will connect the up to 90VDC (10:1) from the voltage divider on the bank to the display board.

The only thing going back to the control box that is over 50v is the low current feedback voltage off the voltage divider, everything else is 12V or below. (5v for the display board etc).

Any suggestions of easily obtainable connectors in australia would be appreciated.

Oh, and I wound my transformer secondary onto a nice little former, and then test fitted the ferrite and clips, and sat there with a satisfied grin, only to notice that there was NO room on it for a primary :P God i was so pi$$ed! I'll be sticking with the flyback core :)

vk2fro

Tue Nov 15 2011, 08:26AM

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

Bus bars look good - solid copper (and cost a small fortune LOL)

Now need a drill press and can get started making the bank proper :)

edit:
found a simplex 4040/vibratone 350 horn on ebay!! now I have a similar alarm to TGG, but this ones 24V ac, so I can drive it with a baby inverter and a transformer (they're cheaper than making a dedicated 24V AC inverter for 12V)

edit 2: looks like I made an error. The horn has arrived. Its 24VDC, so thats easy as I already have a 12-24Vdc converter that has enough current to run it.

I built a timer module to blast the horn at one second bursts. So I just hold down the alarm button and it will automatically do its thing. I finished the inverter (yep transformer finally wound) and fixed an error on the pcb (Which was fatal when the first one got plugged up to 12v), so have ordered a new set of PCB's. These have the bonus of the transformer being onboard, and the hv bridge. They only have one range though - 900V. I've decided not to go with bus bar shifters to make the system dual range (i.e. switch fom series to parallel for 450v and vice versa for 900V). The circuit will however, be adjustable from 50v to 1200 volts, so should be suited to anyone who wants to build one. (will sell them as kits once I've tested them). The hysterisis on the lm 393 has been improved with a 555 timer and relay (for user isolation). Once a charged state is reached, the charger portion is disabled for 5 seconds, to prevent the board oscillating as the voltage rises above and drops below the target voltage. The transformer is based on a philips FX2440 core which will mount right on the board.

Trigger board for the big scr is also on its way as well. You feed it 12V, and to fire, you short 2 pins. Its a seperate board so it can be mounted close to the firing SCR, and thus reduce the chance of false triggering by noise from the inverter board.

vk2fro

Mon Nov 26 2012, 08:44PM

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

Hi folks - this project has been on hold up until now - and now I am having SCR issues.

Each module that I build I test to ensure I dont blow up expensive components (like my hockey puck SCR). I built the SCR trigger circuit on this page:

http://www.powerlabs.org/pssecc.htm

and replaced the trigger switch with a relay so an AVR can trigger it. When I measured the voltage across the gate output (which would normally connect to the gate of the big SCR) and ground, I'm seeing 0V when powered on, and a few millivolts (e.g. 7.6mV) when I fire the relay. Shouldn't I be seeing a few volts here?

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