Made my first ever inverter with only one power transistor - Page 1
Forum section: electronics / projects

author: zeal422
author_rank: Contributor
timestamp: December 12, 2023, 06:25:46 am
content: 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 voltagesThe transistor is a "2SD2500" from an amplifier that I took apart because it didn't work anymore.Here it ishttps://imgur.com/peAssmi.mp4Let me know how bad this is, I'll take it

author: Zero999
author_rank: Super Contributor
timestamp: December 12, 2023, 11:29:41 pm
content: 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.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 13, 2023, 12:27:32 am
content: 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

author: zeal422
author_rank: Contributor
timestamp: December 13, 2023, 05:24:46 pm
content: 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

author: zeal422
author_rank: Contributor
timestamp: December 13, 2023, 05:30:03 pm
content: It's just for learning / fun Tim, no regulation no nothingThe most I drew from it using a dummy load was 80W

author: Zero999
author_rank: Super Contributor
timestamp: December 13, 2023, 10:53:15 pm
content: Quote from: zeal422 on December 13, 2023, 05:24:46 pmSorry, 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.

author: Circlotron
author_rank: Super Contributor
timestamp: December 13, 2023, 11:39:43 pm
content: Definitely post a schematic. Hand drawn one is fine.

author: zeal422
author_rank: Contributor
timestamp: December 14, 2023, 11:10:25 am
content: Quote from: Circlotron on December 13, 2023, 11:39:43 pmHey there... Here it is... I took some time to make this since I'm not a good schematic drawerI wrote the values that I myself used...

author: Zero999
author_rank: Super Contributor
timestamp: December 14, 2023, 10:42:42 pm
content: Quote from: zeal422 on December 14, 2023, 11:10:25 amThere 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=vectorNote the output waveform is a rough square, not a sine wave, which will not power some appliances, although an LED bulb will be fine.

author: zeal422
author_rank: Contributor
timestamp: December 16, 2023, 06:48:41 am
content: Quote from: Zero999 on December 14, 2023, 10:42:42 pmHey, sure thing if you don't mind...

author: Zero999
author_rank: Super Contributor
timestamp: December 17, 2023, 06:37:28 pm
content: 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.

author: zeal422
author_rank: Contributor
timestamp: December 26, 2023, 04:12:28 pm
content: Quote from: Zero999 on December 17, 2023, 06:37:28 pmThank you for the simplified explanation, happy holidays