Temperature sensor / weatherstation

Step 2: Build the RS232 interface

I like to build the 1-Wire busmaster so small that it can just sit in the back of the computer in the rs232 port.

Step 1)
Figure out how small you can make it.
Put all the components on a perfbaord. Place them with the circuit in mind. We don't want to add any wires to the bottom of the circuit! Se image.

Step 2)
Cut out the right size perfboard.
Just drag a sharp knife a few times over the row of holes where you want to cut.
Do this on both sides, then just break it in two. It usually breaks at the fault line you created.

3)
Solder the components in place. and connect the solder points to complete the circuit.

Comments

[andy70707]

Will this interface work with other 1-wire devices such as iButtons? And can it do bi-directional serial (read+write) or just simply reading from the device?

[bhp0528]

I'm a little shy (actually lazy) when it comes to circuit boards and solder. I noticed a similar tutorial was using a http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2982 to interface from serial to RJ-45.

Looking at the documentation it appears this would do the same as your diodes and soldering and give you a RJ-45 to boot. The site appears to spec the device for $21. Any idea how that would compare to soldering diodes in price and functionality?

[bhp0528]

After looking at the site a little longer I found a number of different adapters (USB, Serial, etc). Has anyone tried these?

http://www.maxim-ic.com/products/ibutton/products/adapters.cfm#rs232

[aramja]

Hi - I am new to the electronics field. Is it possible for you to explain why the RS232 interface circuit is wired the way it is. Apologies if this is too basic a question! cheers

[chr]

I'm not totally sure how it works myself :) The basic idea is something like this: The RS232 port (at least according to specification) outputs a high voltage logic signal. -10 and +10 volts, whereas TTL level electronics such as requires a 5v operating voltage, and 0v and 5v logic signal. The DS1820 sensor uses "parasite" power, which means it's powered from the same wire as data is transmitted. The RS232 interface steps down the voltage from the seriell port to 5v to power the device, and steps down the data signal to 5v aswell.. Someone please correct me if I'm wrong here :p

[aramja]

Ok that makes more sense to me now - many thanks for that!