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Just to let you know, it's running fine with a standard 1/4 watt 5R6 surface-mounted resistor.

Thanks guys, and sorry to have troubled you. I've just found that by pressing down on the Darlington array chip (it's surface mounted) everything works fine. So it's obviously a bad solder connection somewhere, or a physical problem with the chip. The effect is the same on all channels, so it...

I'm having a problem with a really simple program that is designed to flash an LED on each of four output channels on an 08M2: main: high c.0,c.1,c.2,c.4 pause 200 low c.0,c.1,c.2,c.4 pause 2000 goto main That's all the code there is -- similar to the example in...

Thanks for the duty cycle explanation. On that basis, my strobe flash is, say (I'll have to check it), 1/5 second duration about every 1.5 seconds, so I can reduce my resistor's wattage by a factor of about 7.5? That could make a 1/4 watt smd resistor viable. Edit: Just checked my code; my...

I've got a couple of those flytron units, but I enjoy building, which is why I make my own. They're not an 'upgrade' compared with mine, for they use the same LED. Also, most of mine are profiled to fit wingtips etc., not plain circular. I'm not electronically savvy enough to figure what...

I've been using Cree XP-E series LEDs as strobes in my model RC aircraft for some years now. Because of the very short duration of the 'on' mode I've been using them without heatsinks with no problems. Running them off 5v supply I've been using series resistors ranging from 2 ohms to 5.6 ohms...

Thanks Hemi. I've got lots of hits for the smaller quantity I want; just haven't got around to placing an order yet.

It seems the reason I can't get it from my pharmacist is that here they use "surgical spirit" for cleaning wounds and preparing for needles. It's based on methyl salicylate and methyl alcohol with castor oil thrown in, perhaps to discourage the usage that hippy has alluded to :)

I intend to use IPA, I was simply being too brief when I said 'alcohol'. I'm surprised I can't get it from my local chemist (pharmacy) given its common useage, but I can get it on the internet, but just haven't got around to it yet. The reason I have acetone to hand is for cleaning equipment...

Follow-up -- don't use acetone! As I mentioned earlier in this thread I planned to use acetone because that's what I had to hand, and it certainly made a good job of cleaning. Two identical boards used for controlling points on my model railway, and one board that strobes lights on a model...

OK, I'd never heard of 'tin whiskers' growing. Google tells me that 'A single accepted explanation of the mechanism has not been established', and one photo shows one growing across two terminals in thin air without any support. Dendrite growth sounds more believable, though that is more...

On reading what people have said about acetone (I use it to clean my equipment when using epoxy resin for fibreglassing) I'll be sourcing some IPA to do my PCB cleaning from now on. I'm resonably confident it was hygroscopic flux that caused my problem, for if it had been a solder bridge --...

techElder, I'm not sure that whether or not it dissolves in water means it can't absorb water and become slightly conductive. Anyway, there's no doubt in my mind that flux was forming a path across two tracks, since removing it -- and not doing anything else -- solved the problem. From now...

Mortifyu, poor choice of resistor values may be a factor in my case because I'm not very experienced at circuit design (though I did take advice on this forum in this case). The circuit appeared not to be damp, and the flux powdered as I scraped it off and, most importantly, the fault was cured...

Thanks johnlong. I have pure acetone, the main ingredient of nail varnish remover, so will use that. Is there any chance that this, or any other solvent, might have a bad effect on components?

I've been making circuits, mainly PICAXE, for many years now and have always left the flux from my resin-cored solder wire on the PCB, as I had read on the internet that it's safe to do so. But recently I've found that it's causing malfunctions on a couple of my boards, causing adjacent...

I've connected four outputs from an 08M2+ to the eight inputs on the UDN2981A in four pairs, with everything running off 5v, and it's working exactly as required. Thank you all.

Thanks hippy. I'll build a circuit that way, and let you know how it goes.

I've now got another application requiring common -ve outputs, so I've got hold of some UDN2981 devices. Can I simply connect their inputs to the PICAXE outputs as I do with the ULN2803 subject, of course, to changing the polarity of the outputs appropriately?

Thanks hippy. My 'not migrated ... ' message had the latest date/time when I looked yesterday -- I think my list was showing latest at the top, as you suggest it should, though I can't be 100% sure. Anyway, around lunch time today Windows 10 had another automatic updating session on my PC (I...