I think about using an Arduino to control my camper which I will build in the following weeks / months. I would like to have a main touchpandel where I can switch on/off led's and some other consumer like the fridge, the water pump and all the stuff you can find in a camper. Now I have some questions about this:
Power supply: how to ensure that the arduino always gets a constant voltage? The voltage in a car can vary between something around 11,5V - 14V. Would a DC/DC converter be a good choice?
Of course I need to switch on/off some consumers. Any advtanges / disadvanteges between a classic relay or a mosfet (which acts like a relay then)? I guess a relay is easier to use but on the other hand it makes noises (the typicall "click").
I already own an Arduino Due which runs on 3,3V. Is it possible to use this anyway, since most relays / mosfets require 5V as an input?
I plan to use several sensors inside the camper, like the ds18b20 and some other. They will be spread all over the car. Do I have to take care about the length of the wires? What about shielded wires?
Hope to get some answers so I can adjust my setup before I start building the furniture. It may be difficult to lay wires after this step
That sounds like a huge project, to build a camper. Good luck!
To run any Arduino powered by the 11.5 - 14.4 I would use buck converters to produce 3.3, or 5 volt.
Depending on the consumers I would use a secondary battery for the consumer section in order to always have a battery for starting the motor.
@Railroader: yes, it will take months to finish this project The electronics will be only one part of the entire project.
And yes, a second battery is defenitely planned. Also solar power and all that stuff.
@larryd: I guess some cheap relays will do their work But I am a bit perfectionisitc ( ) and therefore I think about the typicall "click" sound a relay makes. The more I think about it the more I do not want to have these sounds. I would like to switch all me consumers silently.
In the meantime I found the irf3708 mosfet which could be the missing part I was looking for.
Now, I still have to find an answer to my last question.
Is there a possible issue about wire lenghts and the fact the the sensors are spread over the whole car? Do I always get perfect signals, even if there are some power cables alongside which can carry severals Amps?
Keeping power cables and signal cables apart is good. When the cable lengths grows there are different measures to take like twisted pairs, shielded cable, decoupling caps...... Investigate which cabling looks like being the proper one and start with that. For instance, it's no disaster if one reading per hour makes a jump because of other consumers being switched. Balance the severity of a single error to what it might cause. Filtering, in code, like demanding a few readings giving the same value is one way.
Remember that You're not building a Mars satellite/rover that must work failfree for 20 years.
One more. Don't let the content of Your drawer affect the design of the build. Get the hole picture clear and if necessary, change a circuit and let the old one wait for new missions.
larryd:
I’ve never seen a relay fail. (out of many thousands! )
I have seen transistors fail many times ;).
Let the relay switch enough number of times and You will see it. I once investigated a circuit board that had failed and it was intended for a real space flight. No service cars up there so better use good stuff....
Checking the test, validation procedure, and summing up the number of relay switchings during the test procedure it was discovered that the the expected life of the relay was exceeded....
larryd:
Operations easily exceed 70,000 Specifications, data sheet?
Okay, in 45+ years I’ve seen a few intermittent contacts. The kind of load affects the closing contacts. Both inductive and capacitive loads affect the life of the contact function.
Ds18b20 sensors are 1wire
Wire lengths should be somewhat equal.
If you have some long runs and some short runs you can put them on different pins.
Things like a BME280 that use I2C need to be shorter wires.
I would suggest that you make a place for a remote arduino and run 3 or 4 Cat-6 cables between locations.
While the area is open it is easy even if you never use them.
Possible power. signals. outputs. networking...
I would suggest you make a list of Every possible feature you might ever want, lights pumps heat etc.
Weight/level fuel for heater or water......
Then think what it would take to add them after you are done.
