I ordered the MKR1000 Wifi and 7 capactive soild moisture sensors like these:
The Arduino has 7 analog inputs, that part I'm good.
Next, I will need to give each of the 7 sensors a line of 5V and GND.
Now, I'm a bit of a newbie here, I'll need to split the 5V and split to GND, each into 7 different wires. Is there an elegant way of doing that? Some special connector\splitter, or will I need to solder my own 7 to 1 wire. Is there a good alternative?
Thank you...!
Later Edit: This seems like it could be useful for me, referring to the PCT218, 8 port terminal. So 2 of those, one for the 5V and one for the GND, should that do the trick for me?
Plan to calibrate each sensor with it's own wire attached and keep the calibration values so your program code can use them. Best to number the sensors with permanent marker.
Paul_KD7HB:
Plan to calibrate each sensor with it's own wire attached and keep the calibration values so your program code can use them. Best to number the sensors with permanent marker.
Paul
I realize that they'll have different values and I'll need to mark them accordingly. I'm more worried about splitting the 5V into 7 sensors. Can I just use a terminal like the one in my edit in the original post? And in terms of current, no problem to drive 7 sensors, each with an operating current of 5mA?
moryoav:
The MKR1000 will be powered from the USB port, a 5V/1A. Should be sufficient?
The question was about the power supply to the sensors, not to the Arduino. If you power the sensors from the 5V pin on the Arduino, no problem. If you power the sensors from a digital output pin, which you might do if the circuit was running on battery power and you need to switch the sensors off to save battery power, then that could be a problem.
Your connector idea is not really suitable. Those connectors are meant for mains wiring and may not grip signal wires. They are too crude and overkill for this project.
Do the sensors come with a wire with a plug to fit the sensor's socket? What connector is on the other end of that wire, if any?
Assuming there is no connector on the other end of the wire, and/or you need to extend the wires anyway, I would suggest buying a proto shield for the mkr1000 or build one yourself from stripboard. You can then use 0.1" PCB header sockets to make 3-pin sockets for your 7 sensors. Obviously, to do this, you will need to invest in a crimping tool and soldering iron.
PaulRB:
The question was about the power supply to the sensors, not to the Arduino. If you power the sensors from the 5V pin on the Arduino, no problem. If you power the sensors from a digital output pin, which you might do if the circuit was running on battery power and you need to switch the sensors off to save battery power, then that could be a problem.
The mkr1000 uses a samd21 chip, right? That's a 3.3V chip, so the maximum input voltage on any pin, including analog pins, is 3.3V.
I plan to connect the sensors to the 5V on the MKR1000 board, similar to what's done in the diagram here:
The output voltage of the sensors is 0-3V, so I'm ok with an input voltage per analog pin.
It was just a question of splitting the 5V output from the MKR1000 to 7 different sensors (like the diagram in my link, except with 7 sensors...).
So I understand it should be fine. Maybe my biggest concern should be the AWG of the wires, if several of the sensors are a bit far, that's a different question.
Thank you.
moryoav:
I ordered the MKR1000 Wifi and 7 capactive soild moisture sensors like these: Capacitive_Soil_Moisture_Sensor_SKU_SEN0193-DFRobot
The Arduino has 7 analog inputs, that part I'm good.
Next, I will need to give each of the 7 sensors a line of 5V and GND.
Now, I'm a bit of a newbie here, I'll need to split the 5V and split to GND, each into 7 different wires. Is there an elegant way of doing that? Some special connector\splitter, or will I need to solder my own 7 to 1 wire. Is there a good alternative?
Thank you...!
Later Edit: This seems like it could be useful for me, referring to the PCT218, 8 port terminal. So 2 of those, one for the 5V and one for the GND, should that do the trick for me?
The length of power and ground wires adds resistance but that means you lose a little power as long as the wires are not too thin. You still don't need thicker than 20 ga (jumpers are mostly 22 ga).
What to deal with is how long are the wires with the analog signal, they should be short.
You could put an ATtiny onto each sensor, have it digitize the analog and send that as binary to the main MCU on request. The ATtiny chips can be programmed for I2C and all connect to the same bus wires/pins on the master.
Consider that analog read takes ~105 usecs and time to send data takes a small fraction of that. With 7 sensors you can have 6 busy reading while the 7th is reporting.
GoForSmoke:
The length of power and ground wires adds resistance but that means you lose a little power as long as the wires are not too thin. You still don't need thicker than 20 ga (jumpers are mostly 22 ga).
What to deal with is how long are the wires with the analog signal, they should be short.
Consider that analog read takes ~105 usecs and time to send data takes a small fraction of that. With 7 sensors you can have 6 busy reading while the 7th is reporting.
Ideally, I'd like each sensor to be read once, maybe twice per day, and the sensors don't all need to work at the same time. So I could have very long delays between analogRead(X) and analogRead(X+1)... The most distant sensor will be about 2.5m from the board, the closest will be around 0.5m, the rest will be somewhere in between. Also, since time is not an issue, I could read and average results over a period of time to average noise and such. I guess I'll just try and see. I prefer not to add a digitizer at this point.
moryoav:
I plan to connect the sensors to the 5V on the MKR1000 board, similar to what's done in the diagram here:
That image shows a 5volt Arduino.
The MKR1000 WiFi is a 3.3volt Arduino.
Maybe better to power the sensors from the (regulated) 3.3volt pin of the MKR1000.
Leo..
Wawa:
That image shows a 5volt Arduino.
The MKR1000 WiFi is a 3.3volt Arduino.
Maybe better to power the sensors from the (regulated) 3.3volt pin of the MKR1000.
Leo..
according to this:
If powered by 5V source (like I plan to do with the USB port) then there's a 5V pin for power output.
Would that be a problem?
moryoav:
Ideally, I'd like each sensor to be read once, maybe twice per day, and the sensors don't all need to work at the same time. So I could have very long delays between analogRead(X) and analogRead(X+1)... The most distant sensor will be about 2.5m from the board, the closest will be around 0.5m, the rest will be somewhere in between. Also, since time is not an issue, I could read and average results over a period of time to average noise and such. I guess I'll just try and see. I prefer not to add a digitizer at this point.
Maybe you could calibrate the sensors after setup or make sure all of the sensor wires are equal length and gauge but semi to fully closed loops will cause problems of their own besides being vulnerable to EM interference. Whatever you do, do not coil up a long sensor wire going to a close sensor just to make things neat because that coil will have properties of its' own.
Wawa:
That image shows a 5volt Arduino.
The MKR1000 WiFi is a 3.3volt Arduino.
Maybe better to power the sensors from the (regulated) 3.3volt pin of the MKR1000.
Leo..
I immediately thought the same thing, but then I checked the link in the OP and changed my post, after checking there had been no more responses. Unfortunately, morayoav replied before I saved my change! My bad. But @morayoav please go back and re-read my updated post.
Anyway, the sensors need 3.3V~5V and output only up to 3V which is no problem for the samd21. Better to power the sensors with 5V, then the voltage drop in a long wire will probably not be a problem.