13-04-2013, 09:28 AM
It's amazing what you can get for such low prices! I've been looking to buy some panel meters for work, and of course we can't buy from eBay, so have to use Farnell, RS, etc, and you're looking at many 10s of pounds for just simple meters. For home use, the Chinese copies are perfectly OK, and considerably cheaper.
For example, I've just ordered one of these:
http://www.ebay.co.uk/itm/321104772389?s...K:MEWNX:IT&_trksid=p3984.m1439.l2649
This is actually a pair of them - for £10.70 including delivery! The cheapest LED panel meter that RS sell is £18+VAT, and that's a module that has to be mounted on a PCB behind a window or bezel that you provide yourself.
Of course, it remains to be seen how good they are - the 7107 is a standard chip, but the implementation matters. You have to use a good quality integration capacitor, for example. And if you use the internal voltage reference, the readings can drift slightly (because the LED drivers warm the IC). But, at that price, I don't mind doing a bit of engineering, and the picture implies standard through-hole components and a socketed DIL 7107 IC, so it should be nice and easy to work on. There's even a multi-turn preset! How do they do it?
Back to David's mains monitor, here's the same meter but with a BIN (£11.45 plus £1.30 postage!) - a little more expensive, but saves faffing around with an auction:
http://www.ebay.co.uk/itm/Digital-AC-300...7675.m1850&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D11%26meid%3D6929381957542187014%26pid%3D100011%26prg%3D1005%26rk%3D3%26sd%3D171017630138%26
Very tempting
For example, I've just ordered one of these:
http://www.ebay.co.uk/itm/321104772389?s...K:MEWNX:IT&_trksid=p3984.m1439.l2649
This is actually a pair of them - for £10.70 including delivery! The cheapest LED panel meter that RS sell is £18+VAT, and that's a module that has to be mounted on a PCB behind a window or bezel that you provide yourself.
Of course, it remains to be seen how good they are - the 7107 is a standard chip, but the implementation matters. You have to use a good quality integration capacitor, for example. And if you use the internal voltage reference, the readings can drift slightly (because the LED drivers warm the IC). But, at that price, I don't mind doing a bit of engineering, and the picture implies standard through-hole components and a socketed DIL 7107 IC, so it should be nice and easy to work on. There's even a multi-turn preset! How do they do it?
Back to David's mains monitor, here's the same meter but with a BIN (£11.45 plus £1.30 postage!) - a little more expensive, but saves faffing around with an auction:
http://www.ebay.co.uk/itm/Digital-AC-300...7675.m1850&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D11%26meid%3D6929381957542187014%26pid%3D100011%26prg%3D1005%26rk%3D3%26sd%3D171017630138%26
Very tempting
