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Boost Converter 4.5VDC-330VDC

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youngcoilgunner

Sun Sept 14 2008, 02:34PM

Registered Member #1633 Joined: Tue Aug 12 2008, 04:21AM
Location:
Posts: 45

as someone in an earlier thread in hv forums once posted, a boost converter is limited to charging to 20 times its input voltage. I would suggest using 12v or 24v input, its not that hard and wont take up too many batteries or money. a couple of 9v should do the trick. I have also found that using larger inductances results in a higher voltage, but if you use too high an inductance it will take too long to charge. Also, usually but not always, higher inductances = higher resistances = slower charging time. If you want a schematic, I can repost a link to my boost converter

Marko

Sun Sept 14 2008, 03:02PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

voyagerscout wrote ...

hello everyone
I know this al lot of people asked this question before, but..
I've been trying to make sense of the boost converter schematics from anothercoilgunsite, but, with no result
the only thing is want is a converter that converts 4,5 VDC to 330VDC
the converters out of disposible cameras kinda suck, so...
does anyone have the schematics ?
please?

greetz, Voyagerscout, The Netherlands

Do not use a boost converter for this application. It is the poorest possible solution you can have for stepping up 4.5V to 330V.

voyagerscout

Sun Sept 14 2008, 05:42PM

Registered Member #1696 Joined: Sat Sept 13 2008, 06:01PM
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Posts: 21

I need it to charge capacitors

what should I use? you say boost converters are the poorest possible solution, so...

rp181

Sun Sept 14 2008, 06:01PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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Posts: 1529

use a higher input voltage.

My 555's keep blowing, why is this? im using 14.5v, with 3kohm resistors to limit current. The 555's dont even get hot, the top of the case just blows off (top part explodes, and sparks shoot everwhere)

Firefox

Sun Sept 14 2008, 07:39PM

Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346

I had this problem as well, RP191. I couldn't reproduce the current spike that was killing them, but I had one spectacularly blow in half. I found that shorting the charged cap through a 1000ohm, 10W wire wound discharge resistor tended to fry the 555 every time, though I'm not sure why. Shorting the caps through a .9 ohm wire to explode did nothing to the charging circuit.

The problem went away when I replaced the safety resistor to a normal 500kohm bleeder.

rp181

Sun Sept 14 2008, 11:05PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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Posts: 1529

how does shorting the cap cause it to explode? It works with a 9v.
Once i ran it, but i forgot to connect VCC, the only thing connected to + as pin 4. There was a puff of smoke and a crack came on the 555. I took pin 4 off, and connected Vcc, which then it proceeded to blow up violently (gave me a bruise on my thumb). The weird thing is its been working for a couple of weeks, until now. I the only thing i changed was the 200ohm ressitors where replace with 3.3kohm resistors. I have a 12v voltage reg, ile try it with that.

guitardude012

Mon Sept 15 2008, 12:52AM

Registered Member #968 Joined: Fri Aug 24 2007, 04:54PM
Location: Norman, Oklahoma
Posts: 104

Shorting a 9v can also cause it damage.

Killa-X

Mon Sept 15 2008, 02:17AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Yeah. Like with my gun, maybe something didnt hit the Capacitor lead, but I tryed 4 for a first time, and i felt like u know, either my multimeter is reading WAY off (it is extremely low battery) cuz like, it shoots shit comparing to when i was doing 2 capacitors. But like i said.. I even connected it to my calculator output, aka around 2V.. and it read 150V on its 200V setting.. So im hoping when my charger says "300V" its really like 70V... I had this happen a long time ago where i was like wtf not working, replaced battery, was only using like 1/8 what it said :(

aonomus

Mon Sept 15 2008, 05:41AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

I recently pushed my coilgun to 440V and had my 555 explode, taking out the LM311 with it, I'm not sure exactly what happened but I'm thinking that without 'soft start' the 555 gets subjected to the turn-on current spike/dip and after a while it has some damage done to it. When my 555 exploded I accidentally left the safety bleeder connected.

Killa-X

Mon Sept 15 2008, 05:13PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

aonomus wrote ...

I recently pushed my coilgun to 440V and had my 555 explode, taking out the LM311 with it, I'm not sure exactly what happened but I'm thinking that without 'soft start' the 555 gets subjected to the turn-on current spike/dip and after a while it has some damage done to it. When my 555 exploded I accidentally left the safety bleeder connected.

Poor you...Hope this doesn't ever happen to me when I get to making the booster...

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