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You know sometimes just being willing to try to fix stuff allows you the freedom to buy things that you otherwise would’ve steered clear of, even though they’re not really broken. I was in one of the local guitar shops not long ago; one that sells second-hand pedals. In their pile they had this: It’s an MXR Phase 90 with the back cover missing (and replaced with some electrician’s tape): I asked how much they wanted for it and they told me that it was broken. I said I was still interested, figuring it might be worth my while to try and repair it if the price was right. After some discussion with the pedal owner (one of the guys who works in the shop), they asked me for NT$300 (about US$10), reminding me again that it was broken. I figured for ten bucks it would be worth it for parts alone, so I readily handed over the cash. The guys in the shop were amazed that I was willing to buy a broken pedal. Meanwhile I was amazed that that seemed so strange to them. So I got it home and peeled ...

This regulator was designed for use with a  generator with a higher output voltage. This  type of generator can be found on some boats  and on vehicles for the emergency services.  They are really just an adapted version of the  standard alternator normally found in cars.  The field winding is connected to the 12 V  (or 24 V) battery supply, whereas the generator winding is configured for the AC grid  voltage (230 V or 115 V). This AC voltage now  has to be kept stable via the 12 V field winding. Although it’s perfectly possible to use a  switching regulator for this, we deliberately  chose to use the old and trusted 723. Circuit diagram : Regulator for Three-Phase Generator Circuit Diagram The generator is a three-phase type, with the  field winding rated for 12 VDC. The output voltage of the generator depends on its revs  and the current through the field winding.  Since the output voltage is relatively high, it  is fed via opto-couplers to the 723, which is  used in a standard co...

Principle of Phase Angle Control Top - Output Voltage Bottom - Gate Drive Signal Image source: Wikipedia (http://en.wikipedia.org/wiki/File:Regulated_rectifier.gif) The photo above clearly illustrates phase angle control: output voltage controlled by the gate drive signal applied to a thyristor. What is phase angle control? That is what I'm going to talk about in this article. Phase angle control is a method of PWM applied to AC input voltages, usually the mains supply. Of course, the AC supply could be from a transformer or any other AC source, but the mains supply is the most common input – this gives the phase angle control method its greatest usefulness. It has of course become quite obvious from the title (and I’m sure most of you reading will already know this) that the purpose of phase angle control is to control or limit power to the load. The power device used in phase angle controllers is a thyristor – mostly triacs or SCRs. (There are methods of phase controlling employi...