Mee_n_Mac:
Hmmm, a "9"v battery really isn’t 9v but I thought the Li would supply the <200mA w/o dropping too much voltage. Could be that’s just not the case. If it works for the motor and not the valve and the wiring is double checked then the battery is just too weak for this case. You could try to find a 10V wallwort (that’s something of an odd voltage) or build your own “10v” battery from AA (or other) cells. 8 rechargable NiMh cells in series (like using 2 of [these in series) gets you 10V. You can buy 8xAA battery holders but there’s no reason you couldn’t make on yourself that would look like a crude version of this.FWIW you want to increase the frequency of the Arduino’s PWM which will shorten the time it takes the Arduino to repeat the PWM waveform. That way the on/off/on/off… pulses happen so quickly that the valve can’t mechanically move to follow each on/off command, and the pulsed current through the coil will produce a force that’s proportional to the average of the on/off times. That way the valve doesn’t mechanically flutter (much), it just goes to the position you want. Something that repeats 500 times/sec takes 2 msec to do 1 cycle. Something that repeats 1000 times/sec takes 1 msec to do 1 cycle.
If I may ask, how many $$s was it for that valve ? It just seems very fast (to me) for the kind of $$s I’d expect to spend for a science project.[/quote]
The valve was around $60… I was on a valve hunt for days before I found this one. We are making a water rocket engine to be used on a small rc car and maybe other things.
The same company that makes this valve also has a driver board: http://www.kpiwebsite.com/products-DrvBrd.html
I’m considering buying the driver board to use with the arduino but it requires 12vdc…
I contacted the company and also asked about the driver board… and here’s what I got back:
"The driver board may be a great way to use micro controller to amplify the current to the valve. The driver board can use the control signal from the PWM controller, and amply the necessary current, but it would need to be used with a 12 volt power supply, since you have a 10 volt coil valve. Would you have access to a 12 volt power supply voltage? Your valve will need 180 milliamps, so the power supply would need to handle this.
Regarding the PWM from your contoller: The typical range of PWM hertz is a minimum of 500 hertz, and as high as 10,000 hertz. This makes sense, since the response time is limited to 2-3 milliseconds.
As far as the response time, we have had the mini valve react as quickly as 2 milliseconds from fully closed to fully activated. The response time will be affected some by using water, and if you have any back pressure on the valve, but you may find the valve reacted in your application in 3-5 milliseconds. This is a measure of fully open to fully closed, so smaller changes in the control current may be faster."
The driver board is $$ and I guess that kills my plan to use a 9v… I really need this to be lightweight and not so many batteries!
Any advice? I feel like I should compensate you for all the help! gotta paypal? :-)](https://www.sparkfun.com/products/9835)