Jqf4 solenoid valve, no airflow. Help required

I bought some of these: http://www.tcs-motor.com/en/product-details-193.aspx info shows 3vdc and 115ma

My test rig is as follows. Uno pin 11 with analogWrite value 127 ie im trying to get 50% duty cycle. This goes to base resistor of a 2n222a, emitter to gnd, collector to -ve terminal of device, +ve of device to 5v. The setup is exactly as I would have for buzzer or relay, lazily ommitting flyback diode.

I cant get any airflow in or out of the damn thing. I have varied base resistor, duty cycle, and even used an external psu at 5v, 6v even 9v.

I have measured current through the beast at e.g. 100ma with 6v in @ 50%. This seems to me to be ideal operating point., but no airflow. I even had 175ma through it at 9v with 2.2k base resistor...still nowt.

Other points...I tried 2 or 3 to rule out a dodgy unit. Same results. In all cases mentioned above the unit buzzes (appropriately for the duty cycle if u know what I mean) so it sounds/seems like the thing is working...but it aint! I even dismantled one to see if it had its own oscillator like an active buzzer, but all there is is a magnet and sprung moving coil.its like a tiny loudspeaker in fact minus the cone.

Any ideas?

Try it with DC and a series resistor of about 17 ohms, it could be it is reacting too fast and switching at the PWM frequency.

Or try it with an emitter follower configuration and have a potential divider reduce the 5V out of the arduino to 3.7V to apply to the base. That will give you 3V on the emitter.

JohnLincoln: How about testing the solenoids at their rated voltage, using a couple of AA cells, before using PWM which they are most probably not designed for.

Because its a pump, operated by a solenoid, and need to be pulsed to make it pump. With a single 3v supply coonected, it goes "clunk" exactly once. Using pwm of 6v @ 50% cycle ..if I understand things correctly ... is the equivalent of giving it 3v, but in pulses. Ifs how I drive a buzzer, which works fine. Same result as youd get if you connevted an aa to speaker..youd get one click, not a continuous tone.

Grumpy_Mike: Try it with DC and a series resistor of about 17 ohms, it could be it is reacting too fast and switching at the PWM frequency.

I dont understand...I want it to switch at the pwm speed! It needs to pulse to be able to pump. Are you saying the pwm is too fast? Thatscsomething I hadnt considered. I will try bit-banging it at varying speeds rather than accepting arduinos pwm speed, and publish the results.

Thanks

.I want it to switch at the pwm speed!

Oh, I thought you wanted to use the PWM to reduce the effective voltage because you didn't have access to 3V.

It seems unlikely that you can turn a valve on and off at 500Hz or 1KHz ( depending on which pin you use ) and I am not at all sure why you would want to do such a thing.

Grumpy_Mike:

.I want it to switch at the pwm speed!

Oh, I thought you wanted to use the PWM to reduce the effective voltage because you didn't have access to 3V.

It seems unlikely that you can turn a valve on and off at 500Hz or 1KHz ( depending on which pin you use ) and I am not at all sure why you would want to do such a thing.

Solved. Rather red facedly. For various reasons, not least chinese translation, exaggerad / misleading ebay descriptions and probably some senilty, I thought this unit was a vacuum pump. It isnt. It is just a valve. Doh! And huge embarassment. All is not lost, since my driver circuit is fine to create that one clunk that closes the valve.

Methinks it would be more useful for what im doing (suction cup vertical wall climber) if it were normally closed, as sucking 100ma to keep it closed is a battery killer... I will find a use for it...I might make an air powered AND gate or something....

Sorry for wasting yr time znd thanks to those who replied.

Anyone know where to find a mini vacuum pump?.......mind you in my current state of stupidity I may as well reverse the contacts on my mini air pump