boost converter

[scuba14c]

I tried to wind a transformer, but it didn't work. I used a square ferrite block and wound 1 turn of 24-26 AWG wire on one side and 32 turns on another. What am I doing wrong?

 

[audioguru2]

A single turn of wire doesn't make much magnetism or pickup much in the core unless it is carrying many hundreds or thousands of amps, or unless it is used for low impedance, low level very high frequency circuits like the tiny balun transformer in a 75 ohm TV cable splitter box.
Ferrite is good only for high frequencies.

Try it again with 32 turns on both sides. If the coupling is good and the unloaded transformer doesn't use too much current, try 1000 turns on one side. ;D

 

[scuba14c]

That was what I thought was wrong, I just didn't want to wind so much. I'll report back when I get one wound.

 

[scuba14c]

I want to run this by you before I wind this. I have a bobbin shaped piece pf plastic with a hole in the middle. Can I wind around this and separate it in the middle, and then use a steel rod through the middle? Right now these are the only materials I can get.

 

[Alun]

Or better still go to the local dump, pickup an old TV and use its flyback transformer.

 

[scuba14c]

I tried to use a microwave transformer, but it didn't give me anything. Wouldn't a flyback charge too slowly because it is outputting a higher voltage?

 

[scuba14c]

I found some DC Wall transformers. Would one of these work?

 

[Alun]

Higher voltages will make the capacitors charge up to a higher voltage and higher current sources will make it charge faster.

Microwave transformers connected are very dangerous don't use them unless you know what you're doing as the output voltage and current is more than enough to kill, in fact it's a lot more dangerous than the mains.

Using a microwave transformer in this project is a bit safer, but still dangerous as a 12V pulse can still create a back emf of hundereds of volts on the primary which can be steped up to >5kV.

If you really want to use a microwave transformer in this project connect the mains side to the output transistor but don't blame me if anything bad happens.

A DC mains adaptor transformer is perfect for this, cut it open and remove the transformer, connect the low voltage side to the output transistor and the mains side to the diode and capacitors, if the voltage is too low then try swapping the connections on either the low voltage or high voltage side.

Be warned though big capacitors charged to high voltages can kill you and be carefull the voltage doesn't exceed the maximum rating of the capacitors or the will explode.

 

[scuba14c]

I know the dangers of the capacitors, and the only reason I tried the MOT was because I was out of options until I remembered I had two of the wall transformers.

 

[Alun]

I think in general you're better of using a pre-built transformer rather than winding your own. I've done this before, I used a ferrite cube core from an old PC switcing power supply and it worked though it arced over pretty quickly. I tried again and used a layer of insulation tape between each winding it lasted a bit longer but it arced over again. Winding transformers is very time consuming and you need 1000s of turns on the secondary to get very high voltages and it's very frustrating when they go wrong.

 

[scuba14c]

I think that the wall converter should work, but I have one question. The side that was origionally plugged into the wall and is now my secondary doesn't register with the continuity test on my DMM, but it does conduct when I connect a battery. When the DMM is connected it registers .5 on the screen. Do you know what the number means?

 

[Alun]

The mains side won't register because the resistance is too high,use the ohms setting to measure the resistance, you won't get a valid reading with the battery connected and it might damage the meter as well.

 

[scuba14c]

the battery wasn't connected when I measured it. The charger is only giving me a 2-3 V charge when I use just the transformer. Any ideas??

 

[Alun]

What transformer did you use?

Did you try altering the frequency?

Which sisde did you connect to the circuit? - it should be the low voltage side.

Did you try reversing the connections on either the low or high voltage side of the transformer?

 

[scuba14c]

I don't think I've figured out how to build and/or use the driver yet. Will someone explain how to assemble it and operate it?

 

[Alun]

What materials do you have access to?

I would personally etch a PCB, but you can buy strip board or you could even solder it togeather with bits of wire if you want but I wouldn't recommend it.

 

[scuba14c]

I have it soldered together with wires, but I can't get the switch to oscillate. I have tried it on the boost converter, the converter using the transformer and a flyback driver. Could you give me a diagram showing me how to connect the boost converter driving circuit (what wire goes to which pin, how I start operating it). How do I start the switch oscillating?

 

[Alun]

Try using strip board.
Why are you having trouble with pin numbers?  The circuit you first posted had the pin numbers on.

 

[scuba14c]

The pin numbers aren't the problem, I can build the 555, but the switch I'm using won't oscillate. It only boosts until 30V, with either the boost converter or transformer. I'm not sure if the equipment I'm using is wrong or if I don't know how to operate the circuit.

 

[scuba14c]

Just realized what you were asking. I meant the pins on the IGBT or transistor.