Hello everybody!
In the past month I succesfully worked on a 1-wire DC motor controller, with the priceless contribution of some of you.
Now that I made all the tests and I'm ready to deploy them together with a 1-wire network in my house, I have a newbie question about electronics.
I'll run through the walls two cables: one CAT5 cable for 1-wire and future upgrades, and one power cable to run the DC motors.
For the sake of simplicity I powered the breadboard circuit I made with the same power supply and it worked flawlessly.
The L298 and the motor are powered with 7V voltage which is compliant with the specifications.
Is it better to have separate power and logic voltage supply (with a common ground) or it doesn't matter?
These are the two circuits (do you suggest anything easier than Word to design circuits? :D)
The capacitors size is wrong, they are 100nF polyester ones.
VCC is directly coming from the power supply (+7V), while VSS would come from +5V Arduino supply. Take into account that the cables will be about 40 meters long, and I would power one motor at a time.
Can you test the breadboard version of the circuit with the 40m long cables? Even if the cable is coiled up, loosely, you'd get some idea if there was a problem.
Thank you for the reply!
I tested the 1-wire bus with a 40m CAT5 cable and it worked, but not with a 40m power cable because I don't have such a long wire right now.
I suspect most of the problems could arise when deploying all the controllers, with a few 1-wire bus branches.
If I go for the separate power option, I could have greater flexibility for voltage operation, like increasing it to 9V to power other devices/sensors.
Since they're powered by the same power supply, do you think the common ground should be closer to the controller or doesn't matter?
For the CAT5 junctions do you suggest to use a telecom splicing connector like this below, or just solder it?
PS. This is my 100th post!!!
The telecom splices are usually gel-filled to keep the joint safe from moisture, so that may be an advantage in your application (depending on where the wires need to go). But, they are not designed to carry very much current, just the line current of a phone system.
with a few 1-wire bus branches.
Not a good idea to have branches in a long bus, this causes multiple reflections on the line. Even if it makes the line longer you should stick to a single wire. I would go for a ground as close to the controller as possible, this avoids a phenomena called "ground bounce", that can upset your signals.
Thank you guys for the precious suggestions!
I agree that splicing connector is practical, but from a electrical point of view is it better or worse than just soldering? Because if soldering is better, I'd do it even if it means more hassle
I'll redesign the cables path to use only one really long CAT5 cable. I read on Maxim's application note for 1-wire networks that short "stubs" (like 1-2 meters branches from main wire) are allowed. Do you agree them or should apply just the one long cable criteria everywhere?
One more thing, do you suggest me to buy "The Art of Electronics" book as an answer to all my newbie electronics questions / do you know any book for basic electronics introduction?
There us a 1-wire device call a HUB to deal with branches. A DS2409 Micro-lan (AKA 1-wire) coupler. Actually, it allows you to turn branches on an off... eliminating the conditions that cause 1-wire to fail.
Pwillard, the DS2409 is an interesting device I haven't heard yet.
The datasheet doesn't illustrate clearly a topology with it, but if I understood correctly you would have a primary bus with only DS2409s and several branches, one with each DS2409 with other 1-wire devices.
To save cost and development time, I think I'll go with the one long cable route, and if it doesn't work, cut the cable into several branches and use this.
There is a little about 1-wire over Arduino (I had to write by myself the DS2406/DS2412 sketch which I published here)... is it better to use a dedicated master controller? Does it handle longer wires?
do you suggest me to buy "The Art of Electronics" book
Yes I would highly recommend that book it is very good. I especially like the sections where they give you a circuit and ask you why it will not work.