Just connect 22k fixed resistors across each transistor
base and ground and then you may connect the 50K Dual pot leads across
these resistors, that should imitate a 10k pot variations quite closely.
the 10K resistors connected to the Base of each Transistor and replace with 22K
resistors and connect another two 22K resistors from the Emitters to
Ground . Then connecting the 50K Dual Pot across those connections. Is this
The 10K resistors which are connected from the transistor base to the diode junctions should not be disturbed.
you have connected 10K resistors from base to ground, then replace them
with 22K resistors and connect the POT terminals across this resistor.
base to ground ?? Because I don't .
I want to make sure I've soldered it correctly before I place it into the
Inverter. When I power up the circuit, and I turn the Pot, should the
voltage at the Output of TR1 & TR2 be going Up or Down?
Pot I had was 50K Ohms, I was mistaken. It is a 15K ohms Dual Pot. Do I still
need the 22K ohms resistors, or a different value ?
Since you say that with my PWM circuit the current
consumption of the inverter shoots to a dangerous 14Amps, therefore I
just thought, probably we can solve this by reducing the drive voltage to the gates of the mosfets.
This can be simply done by
controlling the base voltage of the buffer transistors. And that is
exactly what we are trying to do by connecting a variable resistor
across the base and the ground of each transistor.
A 15K pot will do nicely here, so now you don't need anything across the base and the ground except the pots.
discussed earlier, use lamp and ammeter set-up with the inverter and
adjust the 15K pot until the current consumption becomes equal to your
square wave design.
After this, hopefully things should get simpler.
calculation, my original square wave was pulling 2 amps at 12V so that comes to
inverter or just what the inverter uses to run at idle.?
Surely it is the power consumed by the inverter with no
loads (idle) and will proportionately increase as its output gets
circuit with Pot modification, annnnddd Nothing blew up and its running.
I hope this time it starts working.
|Modified sine wave inverter circuit|
meter and PWM circuit, it was drawing 2.1 Amps, but when I tried to adjust
the Pot , nothing really happened ,the Amps did Not increase or decrease, only
when i turned the Pot almost all the way left, it would kill the wave form
,literly stopping the inverter, then turning the Pot back to the right the wave
form would come back and you can hear the inverter run. The whole time the
Headlight did not change in brightness.
were slightly overlapping. Would that not cause a problem?
probe. Unfortunately most laptop Mic's Input is in Mono, one channel. So I can't
test both wave forms at the same time to see if there overlapping.
circuits that are all using the 4017 Chip. I've noticed that none of them have
those buffer transistors that are used in my original square wave circuit.
What if I remove them from the circuit altogether. I've noticed that in all
the other circuits the Clock Input goes directly to the 4017, then out of the
two Outputs that they are using , directly to the gate of the mosfet through a
As long as mosfets are involved I won't be able to
help you. I have made good inverters, but using transistors, so I am
totally out of clue.
The LED test that we performed earlier proved that the two ICs are not overlapping, and that's exactly why we did the test.
So friend now it's totally up to you, and now it has to be completed only through some trial and error.
may try different configurations taking the help of other circuits but
always keep the series bulb connected, it will prevent the mosfets from
blowing off if something goes wrong.
ground of both transistors, this time when I did the Headlight, Ampmeter to
Inverter in series Draw test, I got a reading of 1.80 A, Exactly the same
as the Square Wave circuit, it drew 1.82A
the Gate of both banks of Mosfets, the wave form on the Gate that is driven
by IC2 is corrupt, it is missing a pulse, I've sent two screen shots. The screen
shot that is missing a pulse comes from the Gate of the Mosfet driven by IC2 and
the other screen shot that is not missing a pulse is comes from the Gate of
Mosfet driven by IC1.
You will also have to check the waveform at the diode
junctions to make sure whether its the fault of the PWM section or is it
happening due to the lamp and the base resistor.
I guess it's because of the lamp that's restricting the formation of the waveform.
can perform one more simple test by reducing the output load to the
Mosfets. For this we don't need to connect a lamp in series.
the present transformer with a much lower power transformer, say a
12-012/1 Amp transformer, after this you may proceed with your waveform
checks and also by connecting smaller loads at the output (like a 10watt
120V lamp) and see the results.
A smaller transformer will
definitely stop the mosfets from blowing off and also give us a clue
regarding a transformer mismatch in the present design.
Remember we don't need a headlight lamp in the above modified test design.
junctions and the wave form is good there. I have a small transformer out
of an old 12V 2Amp battery charger ( not sure if this trans is OK to use for
test) , and I connected it altogether with No headlight in series. I
turn on the circuit and it runs but when I check the frequency at the Gate
of Mosfet #2 driven by IC2 it reads over 360Hz, and the same frequency on the
Gate of Mosfet #1 but the wave forms are different, not the same. I,ve sent you
two screen shots. Each shot is labelled accordingly. This has to be happening
because of this transformer , I think. What do you think ?
better. They were on the original transformer, with the headlight in
setup without the Headlight in series, with a couple of sacraficial
Mosfets I have, that I know work with the Original settup. I'll let you know my
OK let's see what happens...........I'm totally helpless without being able to check the practical set-up myself.
was just thinking to engage the couple of idle gates with the diode
junctions and connect their outputs with the transistor base.
This will nicely buffer the PWM pulses and stop them from disorientations.
But then the diode junctions will have to be connected with a resistor of any value across them and ground.
seconds then a mosfet blew up. No Go.
idle gates with the diode junctions " which Idle Gates were you talking
about? Unused gates on the 4017's ?? Not sure what you mean.
I think three gates from IC 4069 are lying idle, we can
pick two of them and use as buffers at the outputs of the diode
I mean the input of each gate will go to the respective diode junctions and their outputs will go to the transistor bases.
But very importantly the diode junctions will need to be grounded through a resistor, any value will do, preferably above 1K.
connections. I've sent a diagram depicting the connections you want , are they
connected OK ???
Please check the attached file.
on both transistors, should I remove them or keep them in the
With the present configuration using gates at the diode junctions, 22k resistors can be removed, they are meaningless now.
Do everything just as shown in the diagram, which I gave you yesterday (all 10k resistors are important).
Swagatam, here the revised circuit schematics for our circuit. This
schematic begins from the Two Diode banks 1 and 2 of our circuit.
are 21K Ohms resistors 1/4 W, and Mosfets Q1,2,3,4 are IRFZ44 , the
Transformer is a Center Tap Transformer 12-0-12 on the Primary side.
rewinding a microwave Transformer, unsuccessfully. When I rewond the New
primary side for 12-0-12 the Voltage Output on the now secondary side
was not what I expected, It was 55V AC, not the 120V AC I expected.
wrong but on this microwave Transformer I have, has it's coils wound in
Parallel , side by side. The other Two working Transformers I have,
have it's Primary coil wrapped over top the Secondary Output coil.
Swagatam is my observation valid about the transformer coils