Hey guys.
I'm looking to building a High V transformer driven by mosfet and everybody here has said previosly to drive the the mosfet PWM-ly. and so i searched on that 555 ic circuits. first made a 4pin CPU fan speed controller as summers here go to 40'C/104'F regularly. complicated to set on thread board but its successful.
Now to run a Mosfet and transformfer.
I googled. most circuits come the same with few exeptions, but THEIRS all work, where mine however refuses to/run transformer...
THEIRS:


MINE:

my Mosfet turns on @4v
my PSU is 17.5V measured@1A max
in simulation:
NOTE:
VCC is not 17/2=8.5V
1)''Whys my voltmeter constant or atleast 0 at 555 & 2n2222 off state???
2)''Whys my voltmeter not @ around 1200(17V*71 turn ratio)???
3)''Why isnt mine working in real life made with all the exact parts???
as you can see mine is the same however i had to in the end add LEDs to "show" me all is working.
*first red to see if freq is changing(before my volt divider and blew 555 red LED was changing, now nothing).Red comes on but doesnt flicker with changing values and cant here my transformer ring to judge either.
*then the green to see if the 2n2222 actually 'opened' for current to flow. as one expects it will /did but doesn't anymore flicker in sync with red LED. the 2n2222 part is ok,it opens atleast.
*then blue LED. i understand that the blue will be inverted to red and green, as simulation shows. but i have NO blue light. I checked my mosfet, it's fine and won't get hurt from this PSU.
555 is ok too, i checked the pin1 vs 2-8 diode values, all under 0.600v
4) So either my 555 parts are wrong,(NB i only have 22nF caps to work with,
5) Or my volts are too low reaching the GATE.?
6) Or wrong mosfet?
7) is it because of no heat-sink?( doesnt get hot as it seems it doesnt go on

I DID TRY WITHOUT 2N2222, also doesn't work, so its the 555 side?

Can any one please help me set this straight.
Please.

 

The LED cannot indicate if the 555-timer is working or not. If the 555-timer is oscillating at a high frequency the LED will be lit and that does not indicate that the 555 is oscillating.

You need to test the 555-timer circuit at low frequencies, lower than 10 Hz.
Use larger resistance and capacitance values in the order of 10 kΩ and 100 μF.

 

If the Red, Green, and Blue Dots are actually LEDs, the Circuit will not work.

If the Red, Green, and Blue Dots are actually LEDs, they will flash so fast that You can't see the change.

If the Red, Green, and Blue Dots are actually LEDs, were are the LED Specifications ?

The MOSFET is completely wrong for this project, ( 0.5 RDS ??? ),
I would be surprised if it wasn't already burned-up.

When driving a Transformer You want an exactly 50% Duty-Cycle.

There are better 555 configurations for insuring a 50% Duty-Cycle.

When driving a Transformer it's generally better to use a Split-Primary-Winding
in a "Push-Pull" configuration.


You would be much further ahead by using a Push-Pull-Regulator-Chip
designed specifically for driving a Transformer. SG3525AN
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Can any one please help me set this straight.

I would try the circuit using component values and configuration as seen below.
Forget the LEDs for now.

 

Hi
1.What for is the big resistor of 1 kOhm in series with transformers primary?
2. Small resistor of about 20 Ohm in gate is recommended, as in the first post
3. It is not a push-pull coonfiguration, so pulse duration to the mosfet should be much shorter than the pauses. Check duty cycle
4. A damping circuit- diode, capacitor and resistor- in parallel to the primary is recommended to protect the mosfet

PS. Add 100 uf capacitor between Vcc and GND

 

Hi
1.What for is the big resistor of 1 kOhm in series with transformers primary?
2. Small resistor of about 20 Ohm in gate is recommended, as in the first post
3. It is not a push-pull coonfiguration, so pulse duration to the mosfet should be much shorter than the pauses. Check duty cycle
4. A damping circuit- diode, capacitor and resistor- in parallel to the primary is recommended to protect the mosfet

PS. Add 100 uf capacitor between Vcc and GND

Hello there. thank you for reply. may i ask why i must add the big capacitor? ive seen them in videos but why do i need them? to smooth PSU ripples?

 

The LED cannot indicate if the 555-timer is working or not. If the 555-timer is oscillating at a high frequency the LED will be lit and that does not indicate that the 555 is oscillating.

You need to test the 555-timer circuit at low frequencies, lower than 10 Hz.
Use larger resistance and capacitance values in the order of 10 kΩ and 100 μF.

thank you for reply. yes i know if they flash too fast i cant see, thats why potentiometers are 20k and 500k, so i can set the freq so i see it, but i get your. lights are on may they do flicker and my problem is mosfet. ill try a different mosfet.

 

most circuits come the same with few exeptions, but THEIRS all work, where mine however refuses to/run transformer...

I've seen lots of things that work on YouTube that don't work for long or work at all in real life. Would suggest you start with a design that is designed to do what you want and forget about copying things you see on YT.

 

IS the transformer suitable? i.e. it needs to be gapped to cope with the DC current in the primary.

 

REally, like posts # 8 &9 mention, except that they were being polite, the youtube (cartoon channel) circuits seem to often lack much relationship to reality, at least the ones that show up here asking for help. So what sort of transformer are you using with this circuit?? Some forms of iron tend to easily become permanently magnetized and after that they tend to resist being more magnetized, which will make a very poor transformer action. There is quite a bit more to producing an adequate transformer than just a turns ratio.
AND, the high-value capacitor across the power supply terminals is to assure that the power is available despite supply connections impedance.
And for your circuit, obviously, the transistor is not being switched on strongly enough.
Specifically, if that circuit and those component values are what was published, the whole thing is an obvious fake.

 

ok then forget the politeness.
guess i hv to state this
i dont have:
*osciliscope, so voltages cant bee seen and multimeter wont pick up output volts,hense my led testers from earlier.
*ceramic caps other than 22nf so my values are built around that
*other IC chips. andly 3 555 left.

my trans is a normal ferrite core from off a circuit board. 3 turn primary, about 220 secondary, ratio of 71 to 1

funny enough how i build my thing like EVERY variable freq 555 mosfet transformer out there, and doesnt work, which means all are fake and people that suggest to me that i must drive a mosfet transformer with 555 is talking rubbish (Moderator: Please be careful of your use harsh language here) then...

*i took away leds. doesnt work. works better in simulation but not real life.
*i know of no way to drive the 2n2222 harder as lowering 2n2222 base resistance seems to lower 555 output volts and increasinging vcc to 15v only marginally raises base voltage in the simulation to 0.740v

has anyone here ever built this circuit so they can help me make my circuit work.

PLEASE

 

Hello there. thank you for reply. may i ask why i must add the big capacitor? ive seen them in videos but why do i need them? to smooth PSU ripples?

555' for proper operation requires supply with low internal resistance. Capacitor will help in this , as your "supply" is a resistive voltage divider. In general, it's much better to use a good and cheap chip 7809' to reduce Vcc

 

It might also be worth stating that 555's come in a few different flavors. And I'm not the 555 expert here, so take this with a grain of salt.

 

OK, so here is a suggestion to evaluate the present circuit with what you have: First, temprarily disconnect the transformer primary positive terminal from the +17.5 line, and add an LED and 1K ohm resister in series with the transformer, that add another capacitor across C1. That cap could be a 0.01MFD, or even a 0.1 MFD cap. The object is to slow the pulses so you can see the LED blink. If it does not blink, then disconnect the LED + resister from the transformer and connect it to the transistor collector, still with the transformer disconnected. That will tell you if the transistor is switching. AND it will be slow enough that the meter can respond

 

has anyone here ever built this circuit so they can help me make my circuit work.

Have you tried the modified circuit in post #4?

 

Have you tried the modified circuit in post #4?

i did this first. took away one potentiometer.... the transistor base gets 720mV to 800mV so its supposed to be activated and does activate it seems. i swopped ou my transformer with weaker one and added an LED on the secondary of the transformer... it seems after soldering a few wires it did work. the light went on an mosfet got hot. but it works only if i touch the drain connection with one finger. i have nooooo idea what that means.. and no matter what i cant get the 555 output voltage through the resistor more. not even at 1 volt. and bypassing that base resistor will blow my transistor as it will shoot the output volts to input volts(in simulation) so i must lower my voltage in the divider to to base accepted voltage.
my stuff on real circuit dont make sense. a divider with equal resistors HALVES the voltage....but i get 12v at Vcc. but 2.2v at output before transistor.... what the hell.

 

OK, so here is a suggestion to evaluate the present circuit with what you have: First, temprarily disconnect the transformer primary positive terminal from the +17.5 line, and add an LED and 1K ohm resister in series with the transformer, that add another capacitor across C1. That cap could be a 0.01MFD, or even a 0.1 MFD cap. The object is to slow the pulses so you can see the LED blink. If it does not blink, then disconnect the LED + resister from the transformer and connect it to the transistor collector, still with the transformer disconnected. That will tell you if the transistor is switching. AND it will be slow enough that the meter can respond

i understand thank you

 

What is the purpose of the Transformer's Output ?

How many Volts @ how many Amps ?

Is the Frequency important ?

Will it remain an AC-Output ?, or will it be Rectified to DC ?
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It seems like the transistor is ON, and it also seems like the very fast pulse rate is preventing you from seeing any problems. And you don't have a larger value of capacitor to get a much slower pulse rate. WITH the transformer disconnected.
But there are a whole bunch of big flaws in the circuit as posted in post #16. First, the supply voltage is way too low for correct 555 timer operation, and using a voltage divider to power a 555 timer IC will assure poor operation. Next, the collector load resistor is too low a resistance, while the current limiting resistor in series with the transformer primary is too high. The adjustments make it better than the first version in post #4, but it still will not work.
FIRST, supply the 555 timer with12 volts DC, and then the evaluation can continue.

 

What is the purpose of the Transformer's Output ?

How many Volts @ how many Amps ?

Is the Frequency important ?

Will it remain an AC-Output ?, or will it be Rectified to DC ?
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bugzapper

1000-2000v planned to use ac volt doubler to make it moooore to dc and safer

freq not important aslong as it works optimally and increase freq means increased volts on output so i would like to make freq adjustable

volt multiplier rectified dc