In the datasheet it says the average input current to the opto is 25mA, thus you can put a 550 ohm resistor between the 555 and opto.

 

its putting out -15.10 volts out of the opto i have to get more optos before i can go any further

 

This is very strange. Maybe you confused the negative and positive terminal of the multimeter. You have to check it step by step.
Start with the power supply and then check the output of the 555 with the scope (peak of the square wave near 15V).
Then check the input of the opto with the scope, there the peak voltage of the square wave will be about 1.2-1.8 V.
Then disconnect the IGBT from the opto and connect a 1K resistor on the opto's output and check the wave form with the scope (peak value of the square wave almost 15V).
Then check the IGBT alone by applying 15V on its gate, make your load just a resistor and check if it switches on/off. If yes and the other part of the circuit works connect it to the opto to see what happens.
Finally, come here and tell the problems.

 

its putting out -15.10 volts out of the opto i have to get more optos before i can go any further

If you want you can remove the opto from the circuit and replace it with a BJT transistor. The opto is just for safety, nothing more.

 

i do have square wave output from opto but only at .o1 on the scope

i put the probes on neg pin 5 and pos on pin 8 it reads 15.10 i put the postive probe on the opto output it is 0 i reverse it and leave postive on pin 8 and neg probe to output it says -15.10


im still having problem grasping how the igbt works im putting the anode of diode on the collector and the emitter is getting a 10k 1 watt resistor to the gate which forces it off emitter is hooked to ground

 

i have some pnp and npn mosfets

 

i have some pnp and npn mosfets

There are no npn and npn MOS.
Do you mean pnp and npn bipolar transistors?
Or n-channel and p-channel MOS?

 

i just looked all the mosfet i have are n channel

i have 2 2n6400 scrs

some cny17f opto couple

nte3048 opto

9014 bjt transitors


i also found one brand new opto i put it in the circuit and it was -15.10v

i just double and triple checked the power going into the opto is 15v pos going into the number 8 pin

 

Don't put the probes of the scope like that, you may destroy it if the probes are not floating. Maybe this is the reason you measure wrong voltages. Always put negative probe on ground. Anyway, it is late here, I am going to sleep and we talk tomorrow. Check the circuit again carefully.

 

thank mik3 its getting late here to i will check it some more tommorow

will talk to you tommorow

 

i took the opto out of the circuit and replaced it with a n channel mosfet that feeds to a p channel fet i now have a 15 postive signal comming out


i hooked it to the igbt with 5 watt 10 ohm resistor and another 10 ohm 1 watt resistor going from the emitter to the gate i tried putting power thru and would not switch on i removed the emitter to gate resistor and was able to turn on what sould i increase the emitter to gate resistor to


i found out the opto will not work if the ground is on the same power supply as the 555 that is why it is pushing out 15-

 

The resistor between the gate-emitter should be 10K and not 10 ohm.

 

i have to pick out some higher rated igbts and order them im pretty much stuck till then any suggestions on what type i should buy i have a 120 volt load at about 14 amps

 

There are MOSFET in ebay at reasonable prices. Have a look there. You can use a MOSFET instead of an IGBT.

 

i tried a mosfet before the igbt i didnt do what i needed it to the two signals entrained and it turned into a half wave dc with square waves imposed on it when i was trying to cut the half wave into 4 half on half of section but it probably my doing and not the mosfets fault since i dont know what im doing

 

i tried a mosfet before the igbt i didnt do what i needed it to the two signals entrained and it turned into a half wave dc with square waves imposed on it when i was trying to cut the half wave into 4 half on half of section but it probably my doing and not the mosfets fault since i dont know what im doing

Can you explain better what happened and provide a diagram. Also, it would be better if you use commas and dots sometime!

 

sorry about the punctuation

i enclosed a digram of the way i tried to make the circuit function with mosfet

 

I told you to interchange positions of the 100K and 1K resistors but you didn't. You are using 5V for the 555 but you should use 15V. Where is the MOS? If the square box on the left of the IGBT is the MOS it won't work. Can you tell us what modifications you did again and clearly.

 

mik3 that drawing was of an old circuit were i tried to use a mosfet

that was the wave form i got out of it and what made me try igbt cause i was told that it would chop up the signal better

the new circuit is exactly as you specified

i dont have any igbts left i should have new ones in a day or two

i called the company to see if the opto pdf might be wrong for the pin 5 and 8

the tech person told me the opto will put out 15- if it is connected to the same power source as the led

 

This circuit didn't work because you were using 5V for the 555. Most MOS need 10V gate-source voltage to turn on. Also, if the MOS was a p-channel one and you had connected its source to ground is an other reason for the circuit not to work. Anyway, for the current circuit take an n-channel mos and connect is source to ground, its gate to 555 via a 10 ohm resistor and use a resistor as your load. Also, connect a 10K resistor between the gate and source and measure the voltage on drain with the scope. What is more, make sure the MOS is able to handle the rectified voltage. What is the peak value of the rectified voltage?