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Topic: Solenoid Issues (Read 1 time) previous topic - next topic


Feb 01, 2013, 03:03 am Last Edit: Feb 01, 2013, 03:10 am by schoolsterz123 Reason: 1
I have two 5V solenoids that I have hooked up to two transistor circuits which are in columns 16-25 in the attached picture. For some reason, the circuit 21-25 makes the solenoid move just fine, however the one that is in 16-20 only makes the solenoid move a very little bit and will only go to its full extended length if its touched with your finger. When the power is removed both will move back to their original position like normal.

At first, I thought that maybe something was wrong with my solenoid on 16-20 but when I switch them, it works just fine. So it seems to be something wrong with the circuit. I'm not sure what could be wrong because I'm using the same diode, resistor, and NPN transistor for each one. They both are connected to an I/O pin (green wire) and the 6V power rail.

I also tried hooking both solenoids onto columns 21-25 but then neither of them move at all unless you move them to the extended position and then will stay there until turned off. I am really frustrated because I can't seem to figure out what is wrong. Thanks for the help!

To complicate things even more: when I attach a 5V motor onto columns 16-20 it works completely fine... just not with solenoids...


Perhaps your solenoids require more current.
Is the 330 Ohm the resistor to the base of the transistors ?
What is the type of the transistor ?
Perhaps the connections are not so good, or the ground on the right is not the same as the ground on the left.


Yes the 330 ohm resistor is between the I/O pin and the Base pin of the 2N2222 transistor. The grounds for both of them are connected to the Arduino and the ground of 6V DC power adapter, they are just plugged in to different ground rails on the bread board but everything is connected.

The thing that puzzles me the most is a motor works completely fine in this circuit but a solenoid does not.


What is the resistance of the Solenoids?
What is the voltage rating of the Solenoid?
If you swap the transistors does the problem swap?
When the Arduino o/p is at 5 volts, what is the voltage at the collector (to GND) of the 2 transistors?
It is hard to see the breadboard wiring, please draw a schematic of the project.

The motor may be a lower current rating therefore it works.
Note: the gain of the 2N2222 is 75 but it can vary.
No technical PMs.
The last thing you did is where you should start looking.


The 2N2222 is a rather old transistor, not well suited to switching the sort of current that your solenoid almost certainly needs (e.g. Vce(sat) = 1.6V max @ 500mA). 2N2222A is better, BC337 is better still, ZTX851 is even better, and a logic level mosfet is best. The behaviour you observe is probably due to differences in the gain and/or saturation voltage of your two 2N2222 transistors. Reducing the base resistor to 100 ohms (assuming you are only driving one transistor per output pin) may help a little.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.


I bought the 2N2222A and ZTX851 transistors with some 100ohm resistors online and will let you know if this solves the problem when they come in. Thank you!

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