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View Full Version : Chatter Has anyone tried any of the cheap DS1820 Dallas Temp sensors from China on e-Bay?



zoopydogsit
01-08-2012, 05:52 AM
Folks,
I was thinking of doing some temperature sensing around the house, and was considering the Dallas DS1820, though they are usually quite expensive. However I've found some unbelievably (too good to be true?) cheap prices for 10 units including shipping. Obviously I'd prefer to deploy more sensors at a cheaper price than few at a more expensive price.....

Has anyone tried these and actually found them to work? Or is this just another rebadge of an existing semiconductor to make a few quick bucks?

$12.88 & free shipping for 10 units, where I'd pay $8.88 each + shipping at Element14, and similar prices from the other guys.
http://www.ebay.com.au/itm/10pcs-DS18B20-DS1820-1-Wire-Digital-Thermometer-Dallas-/180692488653?pt=LH_DefaultDomain_0&hash=item2a121c91cd

I may have to do the experiment, buy one locally, get it to work, then buy the cheapies from China and confirm they are the real thing.

Also, if you've used the DS1820s which variant have you had the most success/prefer.

ElectricAye
01-08-2012, 06:02 AM
... I'd pay $8.88 each + shipping at Element14....

I'm not sure where you're located but Digikey has them at about $5 each, Priority Mail would get them to you in about 2 days if you're in the USA. http://search.digikey.com/us/en/products/DS18B20%2B/DS18B20%2B-ND/956983

Of course it's hard to beat those Chinese prices. Hard to tell if they're counterfeits, too. Until they fry out.

If you work with these sensors, you might have a look at the following thread:
http://forums.parallax.com/showthread.php?136782-There-is-something-wrong-with-Micah-Dowty-s-1-Wire-object-in-the-Obex.&p=1060896&viewfull=1#post1060896

Tubular
01-08-2012, 10:16 AM
Altronics wholesale $2.44ea for 10+, $2.22 for 50+,
But for around the house you will probably be fine off ebay

doggiedoc
01-08-2012, 01:04 PM
Heck, for $12.88US - I'd say just order some. Like tubular said, for around the house tinkering - no worries. If you are building a project for a client though, I'd think twice.

Paul

erco
01-08-2012, 03:57 PM
Yes, I've tried an Ebay China $12 10-pack of DS18B20, and they worked as advertised with a PicAxe. I just gave two of them them a quick go/no go test which they passed, but I can't comment on their accuracy or reliability.

kwinn
01-08-2012, 04:39 PM
Not much one can do about reliability but you can add correction factors to the software for calibration as long as the readings are repeatable.

ElectricAye
01-08-2012, 05:27 PM
Not much one can do about reliability but you can add correction factors to the software for calibration as long as the readings are repeatable.

kwinn has a good point. If they were dumped because their lot was out of spec, then you might be able to tweak their outputs. My recent pack of DS18B20 sensors indicate they were made in Malaysia, so the Hong Kong dudes might be trafficking in genuine industrial surplus, out of spec lots, or "third shift" production runs. Who knows?

erco
01-12-2012, 09:34 PM
http://www.phanderson.com/picaxe sells them for $3.75 each, or in a weatherproof (waterproof?) cable for $6.95. ~2/3 down the page.