My problem is: for certain valves 3/12, there is a delay between my button press and them turning on. The rest of the "healthy" valves turn on almost immediately after my button press. Is this a problem with soldering ? I cant figure out what is going on.
Further note: If I bypass the transistor by putting a wire from the power source to the wires of any of the faulty solenoids directly, it turns on instantly. I think there is a problem with soldering on my protoboard.
Connect LED-Resistor to each problem output. Do they have the same delay?? If so, it's CODE.
If the LEDs are fast / normal, the problem IS electrical. Check the voltage applied across the problem solenoids. Maybe excessive drop in your wiring/transistors?
Also swap a 'good' with a 'bad' solenoid. Maybe they are different?
Voltage drop is the problem, the solenoid isn’t receiving the full 12 volt supply. The lower the applied voltage, the slower it turns on. Measure the different valves right at the coil to see if you can spot a difference, it should be obvious. The highest voltage will most likely be about 11 volts due to the TIP120..
I’d first try a new TIP120, you might have a dodgy transistor.
Second, try eliminating the breadboard or moving the problem circuit to a different spot on the board.
Third, try lowing the base resistor to 470 ohms.
Forth. By now it’s time to find a better switching device as the TIP120 is a really poor choice. In fact, it’s the worst possible device that could be used in the application. A simple npn switching transistor (not a Darlington) would be a better choice, a logic level mosfet would be best.
Can you please post a copy of YOUR circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
What transistor are you using?
Can you please post a picture of your project please?
If you have all your solenoids connected, disconnect the good ones and see if the slow ones speed up?
Thanks.. Tom...
rkubin:
Currently I have a circuit with 12 x 12V 160 mA solenoid valves. I use a GUI for testing so that on the push of a button I can turn on whichever solenoid valve I want. The wiring for each valve is identical and is similar to this: Controlling A Solenoid Valve With Arduino - BC Robotics
My problem is: for certain valves 3/12, there is a delay between my button press and them turning on. The rest of the "healthy" valves turn on almost immediately after my button press. Is this a problem with soldering ? I cant figure out what is going on.
Further note: If I bypass the transistor by putting a wire from the power source to the wires of any of the faulty solenoids directly, it turns on instantly. I think there is a problem with soldering on my protoboard.
Any tips?
Thanks
Do all of the valves have the same fluid pressure?
Do all of them behave identically if powered directly from the supply?
