Joule Thief

[Mk1]

@all

http://www.youtube.com/watch?v=BiIkeFXqRos
http://video.google.com/videoplay?docid=-1815461677597553845

Ok its a old one , but it should look so familiar .

Mark

[xee2]

@ jeanna

Some voltmeters may survive over-voltage, but not all. I have fried a few myself so be careful. I recommend using your 1:10 scope probe when measuring high voltages. Or, make you own voltage divider with two resistors. They should be over 100K each. For example, if R1=R2 then the voltmeter will read 1/2 of Vin. If R1 = 9 x R2 then voltmeter reads 1/10 of Vin.

[TheNOP]

caps use the same calculations as resistors, but not for calculating resistance.

in series voltage capacity are added but capacitance is reduced :
Vmaxtotal = V1max + V2max + V3max + etc...
Ctotal = C1 x C2 x etc... / (C1 + C2 + etc...) or Ctotal = 1 / 1/C1 + 1/C2 + etc...

with caps in parallel :
safe max voltage is the voltage of the lowest rated cap.
Ctotal = C1 + C2 + C3 + etc...

you can add diode in series to rise their max reversed voltage tolerance.
you can make 1 bridge made of  2 or more diode in series, same configuration, instead.

edited : was in a hurry to go to work, sorry.

[Mk1]

@Jadaro

Check those http://www.google.com/patents?id=gEs7AAAAEBAJ&printsec=abstract&zoom=4&dq=toroid+coils&source=gbs_summary_r&cad=0_0#PPA4,M1

http://www.google.com/patents?id=P04zAAAAEBAJ&dq=toroid+coils

http://www.google.com/patents?id=azpvAAAAEBAJ&pg=PA1963&dq=pull+push+toroid+amplification&source=gbs_selected_pages&cad=0_1#PPA1963,M1

http://www.google.com/patents?id=wjs5AAAAEBAJ&printsec=abstract&zoom=4&dq=toroid+coils&source=gbs_summary_r&cad=0_0#PPA2,M1

[TheNOP]

I recommend using your 1:10 scope probe when measuring high voltages. Or, make you own voltage divider with two resistors. They should be over 100K each. For example, if R1=R2 then the voltmeter will read 1/2 of Vin. If R1 = 9 x R2 then voltmeter reads 1/10 of Vin.

a variation of the above

i might be wrong but i think all scope probes are using a 1 meg and a 9 meg ohms resistances.

add a 1 meg ohms at the tip of your probe and using the other lead of the resistor to get the reading will give you a 2x or 11x probe, depending on what the probe is set at, 1x or 10x.
you can use other resistors too like a 2 meg for a 3x or 12x, 5 meg for 6x or 15x, 10 meg for 11x or 20x

so, if your scope is good for up to 200 volts with a 1x,
on 10x it is able to read 2000 volts safely.
at 20x it would be good for up to 4000 volts safely.

for a DMM it is different as you must know the scale's resistance first.
so the voltage divider trick is more convenient.