I have a project that controls two solenoids. I originally set it up with an Uno, and then switched it over to a Teensy 2.0 so everything would fit on a single small breadboard and into a small project box.
Everything works on both setups with the exact same code (except changing PIN numbers for the Teensy), except one thing.
On the Uno setup I have two pins from the Uno go to the respective first pins of the TIP120 transistors that control the solenoids. Pin 2 of each TIP120 goes to the ground of the solenoids. There's a 2.2K resistor between pin 1 and pin 3 of each transistor. A wire connects pin 3 of both TIP120s, and pin 3 from one of the transistors is connected to the ground of the 12V power supply. Lastly the live connections from both solenoids are connected, and then from there are connected to the 12V power supply.
This works perfectly on the Uno. On the Teensy only the solenoid that connects directly from pin 3 of of TIP120 to the 12V power supply is activated. The second solenoid is never activated, even though it's wired exactly the same as on the Uno. Any ideas why this setup would not work on the Teensy?
I've tried replacing the transistors, the resistors, the wires, and nothing seems to help. I can't figure out if there is something electrically different going on because of the Teensy. I can't imagine what that would be, but it seems like there is some difference that I'm not recognizing. Any help would be greatly appreciated.
Its impossible to follow your description of a circuit where you give transistor pin numbers.
Transistors have a base, an emitter and a collector - these names are informative and clear,
use them. Pin numbers are a detail of a package only relevant when wiring up a circuit. Name
all signals.
And the Fritzing diagram is confusing and difficult to trace out, as its a wiring diagram, not
a high level circuit schematic.
Whenever you have two identical circuits where one works and the other doesn't, you simply
have to swap parts until you find the fault, as the fault will move with the faulty part.
“Whenever you have two identical circuits where one works and the other doesn't, you simply
have to swap parts until you find the fault, as the fault will move with the faulty part.”
Swaping can to lead to blowing up healthy devices so care should be taken.
I've been swapping parts and testing everything with a multimeter, and I haven't been able to find a problem, which is what is driving me crazy. That's why I thought maybe there is some fundamental difference with the Teensy.
I'm attaching a newer version of the diagram that shows the wiring a bit better on the original Uno version. Apologizes for not posting a schematic, but I'd likely make a mistake doing that, so I'm more comfortable showing the physical connections in the Fritzing diagram.
