On 18/01/12 12:35, p4trykx wrote: > I like it. I was thinking about DS2482-800 myself but that voltage level > was too much for my skills ;-) > > I was thinking about using Analog Devices I2C isolator ADUM1250 > http://www.analog.com/en/interface/digital-isolators/adum1250/products/product.html > Apart from galvanic isolation I think it can also do the voltage level > conversion. > People use 1-wire for many outside sensors so they are prone to lightning > strikes. > Does anyone know if using ADUM1250 might help for those kind of risks or > optoisolators are better? > ADUM is even available in one Polish on-line shop around $5 so I think > it's popular. > > I've made a serial<->1-wire converter with DS2480B and ADUM2402 isolators > from Analog Devices and it works fine. I'm not sure if the isolation is > needed and in what situations the 1-wire can actually damage the connected > computer. I an imagine some situations when wires get mixed and I connect > accidentally higher voltage to 1-wire also when a lightning strikes nearby > some current can be induced in the wires. Could someone with more > electronics knowledge explain it? > > > Some things I noticed on your boards: > > I've read DS2482-100 datasheet and I think if You want to have strong > pull-up You have to add an external mosfet. Look at the 1 page "typical > operating circut". Strong pull-up is needed for powering sensors in > parasite mode so the supplied current can be high. Without the mosfet the > current flows through internal pull-up resistor which limits it.
Not including the strong pull-up was done to keep costs down, and the board as simple as possible. > Would it be possible to do one side board. It's easier to make it with > toner transfer method at home. Or if it's difficult just minimize > connections on the bottom (blue ones) so people can solder few wires > instead of the layer. With a cost of ~$1 per PCB I don't see that much can be saved with a DIY approach. > You could also add another full GPIO header to attach the > Gertboard(another Raspi expansion board) on top or bottom. Another idea is > to put just a small I2C header so you can connect it to Gertboard which I > think has I2C signals routed to another header. Look at the Raspi site > there are pictures of the Gertboard( I can't give the exact link because > they are on strike against SOPA) The boards are really meant as proof of concept, all the un-used connections are available on additional headers on the board, apart from i2c (perhaps I'll revise the board to include this. > Could you tell me what are those 3 legged parts between two resistors R5 > and R8. Sure, they're N-Channel mosfets to handle the level conversion to 5v for the DS2482-xxx Stuart ------------------------------------------------------------------------------ Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
