Made my first ever inverter with only one power transistor

[zeal422]

Hey, so as the title says...

I don't have that much knowledge in electronics, only been a hobbyist for around a year or less and was focused on HV stuff (which I know can be stupid, etc) so this, I guess, was an attempt at lower voltages

The transistor is a "2SD2500" from an amplifier that I took apart because it didn't work anymore.

Here it is https://imgur.com/peAssmi.mp4 Let me know how bad this is, I'll take it 

[Zero999]

What circuit did you use? Is it just the typical blocking oscillator? Please post a schematic.

I wouldn't bother with an inverter, just to power an LED bulb. There are plenty of 12V LED bulbs available.

[T3sl4co1l]

That poor transistor... all that lead length, the high inductance transformer?

Despite that, the power input seems rather well behaved at merely a few watts.  Clearly one or two of those is going into the bulb, so the transistor can't be getting that hot / unhappy.

Guessing there's no load regulation to speak of? (Switch in a few bulbs on the secondary, does current draw increase proportionally?)

Guessing it won't meet any particular requirements (like load regulation, or efficiency, or noise, or anything else a real product might need), but just as a cute demo or proof of concept, yeah, that's all you need.

Tim

[zeal422]

Just a resistor and a CBB cap. Basically if you bridge the emitter with the base of the transistor with a cap you get what it's known as an emitter bypass capacitor, effectively bypasses the emitter resistor at AC signals, allowing AC signals to appear across the base-emitter junction. That's what I learned... again... I'm a noob at electronics. I also tested it with a nichrome wire resistor that I made... basically a dummy load and was handling 80W with the transistor temp going to 60C but the resistor in the circuit (not the load) almost burnt, so that means (I think) needs a beefier resistor. Again this is just for me to learn, nothing more nothing less

[zeal422]

It's just for learning / fun Tim, no regulation no nothing The most I drew from it using a dummy load was 80W

[Zero999]

Just a resistor and a CBB cap. Basically if you bridge the emitter with the base of the transistor with a cap you get what it's known as an emitter bypass capacitor, effectively bypasses the emitter resistor at AC signals, allowing AC signals to appear across the base-emitter junction. That's what I learned... again... I'm a noob at electronics. I also tested it with a nichrome wire resistor that I made... basically a dummy load and was handling 80W with the transistor temp going to 60C but the resistor in the circuit (not the load) almost burnt, so that means (I think) needs a beefier resistor. Again this is just for me to learn, nothing more nothing less

Sorry, that doesn't make any sense. I've no idea what you're talking about. Post a schematic, you want a serious discussion.

How did you measure the power? A true RMS meter is required to measure the current and voltage accurately and even that might not be very accurate, if your resistor is very inductive, it will have a poor power factor.

[Circlotron]

Definitely post a schematic. Hand drawn one is fine.

[zeal422]

Definitely post a schematic. Hand drawn one is fine.

Hey there... Here it is... I took some time to make this since I'm not a good schematic drawer

I wrote the values that I myself used...

[Zero999]

Definitely post a schematic. Hand drawn one is fine.

Hey there... Here it is... I took some time to make this since I'm not a good schematic drawer

I wrote the values that I myself used...

There is room for improvement, but it's clear enough.

It's a blocking oscillator.

The explanation on Wikipedia is very thorough, but might be a little difficult for an absolute beginner to understand. I can provide a simplified explanation, if you're still interested.
https://en.wikipedia.org/wiki/Blocking_oscillator?useskin=vector

Note the output waveform is a rough square, not a sine wave, which will not power some appliances, although an LED bulb will be fine.

[zeal422]

Definitely post a schematic. Hand drawn one is fine.

Hey there... Here it is... I took some time to make this since I'm not a good schematic drawer

I wrote the values that I myself used...

There is room for improvement, but it's clear enough.

It's a blocking oscillator.

The explanation on Wikipedia is very thorough, but might be a little difficult for an absolute beginner to understand. I can provide a simplified explanation, if you're still interested.
https://en.wikipedia.org/wiki/Blocking_oscillator?useskin=vector

Note the output waveform is a rough square, not a sine wave, which will not power some appliances, although an LED bulb will be fine.

Hey, sure thing if you don't mind...

[Zero999]

The blocking oscillator relies on the fact that a transformer has a magnetic core which can only store a limited amount of energy.

When the power is applied, the transistor starts to turn on, by the current through the base resistor, causing current to flow through the transformer. Current is induced in the feedback winding is connected to the base, causing the transistor to turn on harder. The current gradually increases through the transformer's primary winding, causing the magnetic flux in the core to increase. Once the core is saturated, the flux doesn't increase any more, so no more current can be induced in the feedback winding. The base current now falls, causing it to turn off more.

[zeal422]

The blocking oscillator relies on the fact that a transformer has a magnetic core which can only store a limited amount of energy.

When the power is applied, the transistor starts to turn on, by the current through the base resistor, causing current to flow through the transformer. Current is induced in the feedback winding is connected to the base, causing the transistor to turn on harder. The current gradually increases through the transformer's primary winding, causing the magnetic flux in the core to increase. Once the core is saturated, the flux doesn't increase any more, so no more current can be induced in the feedback winding. The base current now falls, causing it to turn off more.

Thank you for the simplified explanation, happy holidays