With enough inductance you can use a square wave and the inductance will round it out. I typically use a center tap transformer on the primary with VCC to the center, then grounding one side then the other gets the polarity reversal. I have used TIP120s (Darlington) and 2N3055s for the transistors. -----Original Message----- From: email@example.com [mailto:firstname.lastname@example.org] On Behalf Of Jim Brain Sent: Friday, September 13, 2013 11:55 PM To: email@example.com Subject: Re: 9VAC from 5VDC? On 9/13/2013 9:57 PM, Bil Herd wrote: > Do you want to create AC from DC or from AC? (thought is was 5 VDC as > input) AC from DC. A uC will run a 50Hz/60Hz DSS routine, either outputting to a PWM channel or R2R DAC. The output will drive a power transistor to the first pin of the Xformer primary winding. The second pin will be at ground. The secondary winding will then have an isolated AC voltage. Since my AC is rusty, I realize now that 9VAC is 9VAC RMS, which is, as john notes, 12.73Vpeak, or ~25Peak to peak. So, the secondary winding needs to give ~25V. Since the primary will probably have 4.7V PtP, that's 1:5 (gives 23.5V, assuming no loss, which is not realistic, so say 22VPtP, which is 11V peak, or 7.7VAC RMS). Maybe 1:6 would be better. If such a transformer cannot be found, I could build a voltage quintupler (5 power diodes and 5 power caps, I assume heavy caps), but I'd rather let the transformer bump up the voltage. Either way, the transistor need to support 5A of power. If 1:3 can be found, I could create two half wave PWMs/R2R channels. With 4 transistors, I could drive the 5V through one way for half a cycle, then the other way for half a cycle, but that means I'm only drive 4.3V (2 PN junction drops). If I use the PWM into some FETS and do the filtering on the output of the FETs, I might be able to do 5V swing, but I am much less familiar with FET operation, so I would have to breadboard it. It also would then require larger capacitors and higher wattage resistors. Jim Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing listReceived on 2013-09-14 04:01:56
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