DrV

As it happens I've just made up a dimmer to control 12 independently dimmed sets of a.c. fairy lights for an amDram show. I've chopped the sets up into 12 volt sections. You identify sections by finding the place where there are only two wires between adjacent LEDs rather than three. Each section is 3.1V so 4 sections makes a nominal 12V length. I'm then driving them through L298 stepper motor power modules. One output of an Arduino Mega provides a square wave at about 1kHz and this drives the direction inputs of all the modules and the enable inputs come from the rest of the PWM outputs. The dimming is rubbish at the bottom end, as expected, because the PWM outputs are only 8bit, but otherwise it works fine. The 12V supply has been tweaked up very slightly to compensate for the slight forward drop in the modules. You do need to monitor the current when setting it as there are no series resistors. Each L298 has two H-bridges so can drive two sets and they were only about £1.50 online. The PWM frequency for the enable pins is set higher than the default at 3kHz. Dave

I used one of those little 3 pole things with a locking ring. CPC AV15047 and AV19316. The panel mount plug has a small enough footprint to fit inside and it has the advantage that it locks. Actually there's a thread on here which includes those two parts and a Behringer desk - maybe that's the psu you want??? http://www.blue-room.org.uk/index.php?showtopic=54311 Edit to add - just realised it's THIS thread! Time for bed...☺

My limited experience with the PSUs is that they do indeed put out a pretty well regulated 31v and I think mine were rated at 110mA for a 100 light string i.e. 10 lots of 10 LEDs running 11mA each. I also tried running them from 24v but they didn't come on until about 27v IIRC. I believe they don't have any current limiting resistors so the voltage is critical.

... one of whom could be the puppeteer with the false arm trick.

You would need to check with vendor but that looks like a single 18V transformer. You need a centre tapped transformer (18-0-18). There ARE 3 wires on the output lead but one of them might be connected to mains earth. As I say, ask the vendor whether it is 18-0-18. Dave

That's the nasty little 3 pins in a row thing isn't it? Best thing to do with it is drill a hole in the back panel and fit a proper connector. Horrid little thing...

If the mics have just a single core and a screen then the only way to wire it is so that the core (pins 3 & 4) goes through the adapter to the tip. No other connections needed. The voltage you see is expected as this is the bias which is supplied through a 10k ish resistor by the pack. I would expect the SMT part to be a resistor rather than a cap as some packs supply the bias separately and you are expected to provide your own resistor, chosen to match the mic spec. HTH Dave

IIRC that means it thinks the lamp has blown. P &T freeze so it doesn't scatter broken glass everywhere. Check the output from the light sensor. Seen many of these which have cooked Dave

I think this is a good point although... I think what you mean is that when the choke saturates it will become a lower impedance as it becomes purely resistive at that point. Net result is the same - less impedance in the way -> higher fault current. The opposite would be the case the rush of current would in fact be filtered since it is a "high" frequency occurence in contrast with the normal 50Hz mains load. True up to the point where the choke saturates, but we are dealing with a fault current here. And the chokes in your average dimmer rack aren't of such vast reactance that they offer any substantial impedance to 50Hz - they are designed to filter out the sharp edges caused by the semiconductor switching. Consider the risetimes quoted in dimmer manufacturers' literature; 100uS standard, 450uS for a quiet version. Dave

I think this is a good point although... I think what you mean is that when the choke saturates it will become a lower impedance as it becomes purely resistive at that point. Net result is the same - less impedance in the way -> higher fault current. And regarding the issue of fitting devices with the right gate sensitivity, the only place I have seen sensitive gate devices fitted has been cheap sound triggered disco lights where there is very little electronics between the mic and the triac. Even the cheapest dimmers usually have a "proper" firing circuit, either using a pulse transformer or an opto/opto-triac. In the repair business it makes sense to fit a high current device - the cost differential is negligible, but when you are buying thousands of them perhaps manufacturers sometimes make savings where they shouldn't. Dave

The current itself is not all that meaningful in relation to popping a fuse rather than a triac - it's the I2t value that is important. At the risk of asking the bl33ding obvious are you using quick blow fuses? Sorry - had to ask - years of tech support phone calls which end with "you have plugged it in haven't you?" :blink: Dave

Just possible that the two steppers are not aligned with each other i.e. when one of them is on phase 0 the other one is between phase 0 and phase 1. To correct it you have to power the unit up and, with the head stationary, you loosen one of the motor pulleys then tighten it up again. This allows the motors to match up. HTH Dave