Hi! I'm a newbie in Arduino and eletronics, but I'm loving it!
I'm thinking in a project that should use 6 independent 5v solenoids like this one from Sparkfun:
Reading about solenoids, I have found a lot of material about higher voltages solenoids, but almost nothing about these of 5v. I had read also something about the necessity of a diode to protect the circuit because the solenoid could act like a generator.
So, I'm asking for some guidance about how to build the circuirt using 6 independent 5v solenoids with Arduino Uno R3.
In the comments at Sparkfun, someone wrote that it is 240mA.
So you need a seperate power supply of 5V for the solenoids.
When the solenoids are switched off, the inductance of the coil will generate a voltage peak that could destroy electronic components. A fly-back diode will allow that current to "fly back" and stop the voltage peak.
The Arduino can control them with transistors or darlington transistors or mosfets or chips. What do you prefer ?
The ULN2803 has 8 darlington transistors + 8 fly-back diodes. But the solenoids will get only 4V instead of 5V.
So, It will be necessary two independet power sources, one of 5v to Arduino, and another one of 5v for the solenoids, is it correct? I will search about the best way to do that.
About the transistors, I will need to study about them, all of this is really new to me. Seems to me that the ULN2803 is the best option, but how the solenoid should act with 4v?
So, It will be necessary two independet power sources, one of 5v to Arduino, and another one of 5v for the solenoids, is it correct?
You can have the same external power supply for botht he arduino as well as the solenoids BUT do not supply power from any of the availabe ports on the arduino like 5v or VIN to the solenoids , in other words keep the power source connections to the solenoids external to any of the header pins on the arduino.
Seems to me that the ULN2803 is the best option, but how the solenoid should act with 4v?
The solenoids may work ok-ok with 4v but they may undershoot or not be reliable at times as their coil is not getting enough voltage so this may not be dependable , you can use TIP 122 or other similar sort of power transistor to actuate and control the solenoids,