Hey all,
I've built a power inverter, just out of curiosity of mains re-generation. I figure if I can get it going, I can plug in a mobile phone charger and charge my mobile in the car.
I mean, it ain't going to power much more.
Basicaly, I took a sine wave generator from here:-
http://www.national.com/nationaledge/jun04/article.html
At appx50hz, it feeds an old PA amplifier from Maplin Electronics, a TDA 2005 amplifier with a microphone input, and a power transformer in reverse to step up the output from the amp up to 240volts.
I've only been able to get 215 volts so far.
The secondary impedance of the transformer is 00.3 with my meter set to 200ohms range! I take it that, its a 3 ohm load which the amp sees. This must mean maximum transfer of the amps output through the transformer.
Would their be a good enough drive from the oscillator to the amps input, seeing its a microphone input? The volume has to be cranked right up. Without a scope, I can't work out much.
I assume the microphone for this amp, would be a cheapy cassette type of thing, rather than battery type. My supply voltage is 12 volts/car battery and please don't suggest I buy a mains inverter 'cos they're cheap enough. I want to learn, and I'm using what I have to hand. I have made a similar version using the PC to generate a wave, and a 50watt amp and drove a Cassette deck and a CD player with it.
Can you help, remember, I'm only wanting to power a mobile phone charger.
Cheers Mike 😕
I've built a power inverter, just out of curiosity of mains re-generation. I figure if I can get it going, I can plug in a mobile phone charger and charge my mobile in the car.
I mean, it ain't going to power much more.
Basicaly, I took a sine wave generator from here:-
http://www.national.com/nationaledge/jun04/article.html
At appx50hz, it feeds an old PA amplifier from Maplin Electronics, a TDA 2005 amplifier with a microphone input, and a power transformer in reverse to step up the output from the amp up to 240volts.
I've only been able to get 215 volts so far.
The secondary impedance of the transformer is 00.3 with my meter set to 200ohms range! I take it that, its a 3 ohm load which the amp sees. This must mean maximum transfer of the amps output through the transformer.
Would their be a good enough drive from the oscillator to the amps input, seeing its a microphone input? The volume has to be cranked right up. Without a scope, I can't work out much.
I assume the microphone for this amp, would be a cheapy cassette type of thing, rather than battery type. My supply voltage is 12 volts/car battery and please don't suggest I buy a mains inverter 'cos they're cheap enough. I want to learn, and I'm using what I have to hand. I have made a similar version using the PC to generate a wave, and a 50watt amp and drove a Cassette deck and a CD player with it.
Can you help, remember, I'm only wanting to power a mobile phone charger.
Cheers Mike 😕
Hi Mike,
Regeneration has been discussed here before: http://www.diyaudio.com/forums/showthread.php?s=&threadid=18066
- and I stand by my summary of playing with my investigation of the approach you're basically trying, which is here: http://www.acoustica.org.uk/other/mains_regen.html
The reason you're not seeing all the voltage you expect at the ouput of the transformer is because the DC resistance doesn't matter mmuch. You're stepping -up voltage, which goes linearly as the ratio of the windings - but impedance is transformed as the square of that ratio. So the amp has to drive the losses in that transformer at such a loss. The cruel outcome is that voltage regulation at high step-up values is...very poor unless you wrap a feedback loop around the whole transformer (which you can only do at low frequency before the system ocscillates due to phase shift in the power transformer..!)
Don't let this stop you trying, it's very informative to play like this!
(Now the unhelpful part - if all you want to do is charge a mobile, you can simply use an LM317 - use your car's raw supply as input, and set the 317 to the required Vin for the mobile 😉 )
Regeneration has been discussed here before: http://www.diyaudio.com/forums/showthread.php?s=&threadid=18066
- and I stand by my summary of playing with my investigation of the approach you're basically trying, which is here: http://www.acoustica.org.uk/other/mains_regen.html
The reason you're not seeing all the voltage you expect at the ouput of the transformer is because the DC resistance doesn't matter mmuch. You're stepping -up voltage, which goes linearly as the ratio of the windings - but impedance is transformed as the square of that ratio. So the amp has to drive the losses in that transformer at such a loss. The cruel outcome is that voltage regulation at high step-up values is...very poor unless you wrap a feedback loop around the whole transformer (which you can only do at low frequency before the system ocscillates due to phase shift in the power transformer..!)
Don't let this stop you trying, it's very informative to play like this!
(Now the unhelpful part - if all you want to do is charge a mobile, you can simply use an LM317 - use your car's raw supply as input, and set the 317 to the required Vin for the mobile 😉 )
I'm getting Deja Vu. What's going on Mike me old breakfast cereal? 😉
PS I have emailed you over the past few weeks and got no response.
PS I have emailed you over the past few weeks and got no response.
Actually, all what you need (because mobile phone charger 99.9% SMPS), it's 340VDC. You can use 12/340 push-pull invertor, e.g. typical caraudio ones contains: tl494; pair irfz44; 1" toroidal ferrite trafo; rectifier.
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