Your capacitor selection depends entirely on it's role in the circuit. Different ones are best for different applications, that's why there's so many! I'm sure one of the senior members here would elaborate further on which types are most used for what. What circuit are you using them in?
No idea, Lefty! It's not my design But the test itself has been unchanged for years... I can only assume those who designed the setup know what they're doing.
The sounders don't actually come with seal tabs on them (which seems odd, as all the ones I've actually bought came with them and I don't normally pull them off until I'm done with them). If the IPA has done something horrible to the innards then I suppose there's little I can do other than apologise and make some more...
I wonder, is it worth opening one up completely to investigate any possible internal damage? We've got thousands on the shelf so I could compare a new one to one that I've molested to see if there's any difference.
Electrical noise is unwanted signals causing undesired operation. Imagine if you're trying to listen to a faint tone against a background of loud static... in simplest terms it's a little bit like that.
EDIT: Here's a thing on RC filters to get you started.
I had a minor mishap at work today and I'm hoping you guys might be able to shed some light on it. I was doing something in work involving attaching wires to sounders - a simple job. Sounders in parallel at one end, hirose crimp connector at the other. For some reason, even though they continuity tested OK, they failed their functional test in which a signal is pumped in and the dB levels measured - they were far too quiet and some sounded crackly. We can't find any problems with the test gear itself, and it doesn't look like there's an issue with the brand new ones in the tube.
Can these things be damaged by cleaning with IPA after soldering? I'm wondering (and it is a bit of a long-shot but so far we can't figure out why they're buggered) if flux residue dissolved in the IPA has gone up inside the thing and hardened again, messing with the little diaphragm somehow. Any ideas on what to try? It'd be nice to rescue them and not have to re-do the entire lot.
At work, I use a 120W iron normally set to 320C, and leaded 60/40 solder. Gets up to temperature and transfers heat to the workpiece quickly, and with the occasional tip-change the same iron works for everything from soldering shielding tape over everything, doing wiring looms, connectors and sticking stuff on PCBs. I'm hardly an expert (although I rarely fuck anything up so badly it can't be re-done), but the golden rules for me are:
1) Plenty of flux 2) Clean EVERYTHING with plenty of IPA before working on it 3) Keep that tip tinned and shiny 4) Use the brass brillo pad things instead of a wet sponge
Lead-free solder is horrible, nobody I work with likes it, and thankfully we're not required to use it due to an exemption. I'd NEVER use the stuff at home either. Just wash your hands after handling it and there's no real harm... although good luck finding it at Maplin these days!
I think the gate-to-ground resistor is there to pull the gate low and keep it there unless something drives it high on purpose, to prevent accidental or unwanted switching. Could be wrong... but I seem to recall that's what it does.
You'll probably need to fit an external 16mhz crystal and a couple of 22pf caps. Taken straight from an UNO, the fuses on the chip are going to be set for an external crystal which you'll need to provide if you want it to work. Have a look around for some arduino to breadboard circuit diagrams and you'll get the idea.
Also, I would consider slightly more beefy batteries. I can't see a couple of coin cells lasting very long if they power it at all... but that does depend on the power requirements of your project, which I can't guess at without measuring it