NE555 smps (Nixie)

[demym]

Hi,

i am going to build a NE555 smps as seen in the many tube threads:




I have some questions priori to handle those voltages:

1) can i measure Vout using a multimeter, as i would do with any 9V circuit ?
2) what is the correct procedure to discharge the big 2.2uF cap (rated at 400v) ?
3) shall i need some particulare type of resistors for this scheme ?
4) does 1N4007 equivalent to the UF1004 shown in the schematics ?

Thanks a lot in advance !

[Pigyboy]

1. Yes
2. Screwdriver tip (I did one with my finger the other day and it is just a tiny pinch)
3. No
4. Yes

[demym]

Thanks very much !

I forgot one thing: really no heat sink is needed for this smps ? (that's what i understood reading the bug multipliers thread)...

[frequencycentral]

4) does 1N4007 equivalent to the UF1004 shown in the schematics ?

NO NO NO NO NO!!!!!

The UF4004 is an ultra fast recovery diode. IN4007 won't work.

[frequencycentral]

Thanks very much !

I forgot one thing: really no heat sink is needed for this smps ? (that's what i understood reading the bug multipliers thread)...

I always use a heatsink. The MOSFET will get really hot under load. Overheating will cause it to slowly die.

[defaced]

2) what is the correct procedure to discharge the big 2.2uF cap (rated at 400v) ?

The correct way is to put a bleeder resistor across the cap.  Something like 220k, which is the ubiquitous value in tube power supplies.  You will need to pay attention to the break down voltage of the resistor, 400v is enough to move some electrons across a resistive barrier.  

4) does 1N4007 equivalent to the UF1004 shown in the schematics ?

No.  UF is an ultra fast response diode.  Being that this is an SMPS, it may very well depend on that faster response time.  If you post a schematic (layouts are great for some things and not for others) we can see what's going on and comment further.  

[Pigyboy]

4) does 1N4007 equivalent to the UF1004 shown in the schematics ?

NO NO NO NO NO!!!!!

The UF4004 is an ultra fast recovery diode. IN4007 won't work.

[frequencycentral]

^^^^

(points and laughs)























(runs away)

[Pigyboy]

OK, I'll wear the Scarlet L(oser)!

[PRR]

> put a bleeder resistor across the cap.  Something like 220k

R1 VR1 R2 act as a 221.5K bleeder, ASS-uming wiring is correctly done. (Vero makes me cross-eye.)

Time-constant is 2.2uFd times 221K or a half-second to reach 37% of normal voltage.

And yeah the operating frequency is probably too high for a 1N4007, use the speedier UF part.

> really no heat sink is needed for this smps?

If everything were perfect the heat would be zero.

Using modern fast MOSFET, fast diode, fat coil, and a very sharp pencil, the heat in any part should be less than 5%, maybe 2%, of the output power.

An odd-parts project is liable to have 5%, 10%, or more losses in some part. That will be HOT.

[Renegadrian]

http://www.diystompboxes.com/smfforum/index.php?topic=74088.0

that is the topic dedicated to voltage multipliers. the nixie has been discussed there and also  you'll find its schematic on the first page.