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LAN_403

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Wed Mar 08 2006, 05:54AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

WilliamN gave a pretty detailed description of what he used... There is a schematic in the thread somewhere. I wouldn't worry about the mosfet driver, just use the 10ohm resistor and 12v supply for the 555.

For a project like this I would stay away from a mot. You could get a 240v->something wall transformer and plug the output into a corresponding 120v transformer to give about 340v when full wave rectified... Add a few 1n4007's and 5uf caps and you have 700w to play with. And it will be limited to a few watts, so it won't be as dangerous as a mot (but still should be considered deadly, especially when combined with a cap)

Good Luck!

Michael Witt

Wed Mar 08 2006, 01:35PM

Registered Member #282 Joined: Sat Mar 04 2006, 11:45PM
Location: North Chicago, US
Posts: 28

The only reason I was thinking about a mot is because I can talk to a guy at my dad's work who can probably get me some BIG caps.
(The company he works for is G. T. Schmidt, a company that makes Nd:YAG and (recently started making) CO2 pump lasers for marking, they are the ones that make the lasers that mark most GM vin tags visible through the car window) and they usually have a few extra caps. He's already given me 5 PC-104 computers, and a dozen good stepper motor controllers; so I'm sure he'd be willing to give me a few extra caps, or a PS from one of the lasers.

[Added:]
I'm working on a PS now, I should have it posted in a little while.

Simon

Thu Mar 09 2006, 01:25AM

Registered Member #32 Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549

That circuit looks okay, except using a resistive divider for any major power control is inefficient and inelegant.

If you can design a circuit to disconnect the charger when the cap is at the right voltage (op-amp + relay, for example) then using the undivided output from the PSU will be a much better solution.

Michael Witt

Thu Mar 09 2006, 01:38AM

Registered Member #282 Joined: Sat Mar 04 2006, 11:45PM
Location: North Chicago, US
Posts: 28

I guess I've been obsessed with resistive dividers recently....
I was also thinking it would be cheaper than anything else...
and I don't know any other ways

How would the Op amp work? As an inverter, controlling a relay, the NC side being charging, the NO side being done charging? Then how would I get the voltage down to the right voltage so that it doesn't blow up the chip? (resistive divider?

)

What capicatance/voltage should the cap be?

One other thing, know any way to make a light / LED indicating thet the cap is done charging? Like the way you see in a flash unit in a disposable camera?

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Thu Mar 09 2006, 02:18AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

what is the device in the center of your schematic? A camera charger?

The easiest way to make this work would be to get a logic gate that has hysteresis on the input (a mosfet driver would e great), and use a resistive divider from the cap to the input of the ucc chip. Use the bleeder resistor for the cap(s) as one half the divider, and use a variable resistor about 1/5 of the bleeder cap for the other half. Hook the mosfet driver in the middle, and use the output either to control the charger directly, or use it to control a relay (make sure to have a diode antiparallel to the coil so that inductive spikes don't kill the driver), or a mosfet to control the charger. Adjust the put to get it to stop ate the right voltage.

What cap are you referring to?

To make a neon light that flashes when there is power put a small (like 1ufd) cap in paralel with a neon light, and hook it across the bank with a 1meg resistor. It will start to flash arround 90v, and flash faster as the voltge rises. Adjust the cap to change the brightness and the resistor to change rep rate.

good luck!

Michael Witt

Thu Mar 09 2006, 04:11AM

Registered Member #282 Joined: Sat Mar 04 2006, 11:45PM
Location: North Chicago, US
Posts: 28

I'm trying to avoid mosfets, because I don't really get them. And what is hysteresis?

The cap I am referring to is the only cap in the PS schematic, it is just before the transformer (what will be used is an arc suppressor/snubber network cap from Mallory). I was just wondering if you would reccomend a capicatance and resistance.

The thing in the middle is just a transformer. The transformer would probably be just an isolation transformer, put after the rectifier.

I'm sorry the diagram is so small, I just don't know of any easy to print directly from my schematic program to an image.

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Thu Mar 09 2006, 05:09AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Hysteresis has to do with how the gate is triggered. I gate with it will only change state if the incoming voltage gets a certain voltage from the trigger point. So it a gate has 100mv of hysteresis and would normally trigger at 2.5v it would only change if the voltage dropped below 2.4v or go above 2.6v. It is is anywhere in between it just keeps it old state.

in order for a transformer to work it needs AC, in your schematic I only see it getting DC...

I don't have any suggestions on the cap.

Michael Witt

Thu Mar 09 2006, 11:58AM

Registered Member #282 Joined: Sat Mar 04 2006, 11:45PM
Location: North Chicago, US
Posts: 28

Oh yeah, I forgot that I need to put the rectifier after the transformer. Thanks.

[Added:]
Anyone know about Jameco ValuePro Caps? Those caps work out to be something like $0.13 per joule, but I don't know anything about ESR/ESL on them. Anyoneone had experience? The P/N for the one I'm looking at is 203246CB on Jameco's site (jameco.com).

Effilcdar

Sun Apr 22 2007, 08:19AM

Registered Member #655 Joined: Wed Apr 18 2007, 10:23AM
Location:
Posts: 14

Trust me get a variac. (variable auto transformer)and an up step transformer. That way you can fine tune your voltage going to the rectifier. Its very easy. I even managed to get it to work.

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