Quote from: wanderson on Aug 15, 2012, 09:29 pmYes logic level, means that the gate will respond when at 5V.Yes, I believe a MOSFET is the most effective method, I do not like relays and if the motor for the pump is DC, you can use a MOSFET with PWM to adjust the power of the motor (but it is not a linear relationship), which you can't do with a relay.I had decided on using a MOSFET over a relay, I was trying to be even more general than that. Keep in mind I'm clueless about most of this stuff.So do I have to specifically get a MOSFET that supports PWM right? Any model suggestions?Also what do you mean by it is not a linear relationship? How accurate do you think I can get? How could I improve this?Sorry for so many questions, I just need to be pointed in the right direction here and I can take it from there.
Yes logic level, means that the gate will respond when at 5V.Yes, I believe a MOSFET is the most effective method, I do not like relays and if the motor for the pump is DC, you can use a MOSFET with PWM to adjust the power of the motor (but it is not a linear relationship), which you can't do with a relay.
No, any MOSFET will work with a PWM technique, but the motor itself might not. By linear, I was referencing the fact that at 50% (AnalogWrite(2.5) the there might not be enough voltage for the motor to work at all. The range of control may be much less.
Here is an Application Note, that may help you for this project; the note itself is for PIC's, but the techniques should be the samehttp://ww1.microchip.com/downloads/en/appnotes/00857a.pdf
Yeah, but I'm thinking though, if I do that, why use PWM in the first place. It was suggested here, I actually hadn't though of it, I planned to do analog straight to the mosfet then to the motor.
the reason for using PWM instead of DC control (a variable linear regulator) is that a linear regulator or variable voltage power supply dissipates the "Unwanted" power as heat. So at low flow rates the DC power wasted will make the control element quite hot. A PWM power supply only has two states off and on, power is controlled by the period of the on signal as it gets narrower in relation to the off period the lower it's "Average voltage" is and the lower the speed the motor runs at.
I think I'm missing something here. Can't I put out a low voltage directly from the Arduino with an analog pin? Nothing should be wasted in that case.
Perhaps part of the problem is we're not being exacting with language.There isn't an analog out (AO) pin on the Arduino.There are only digital outputs (DO).Some of the DOs are PWM.A PWM DO can mimic an AO in some cases.To further confuse things, analogWrite() is used to set the PWM rate.
I'm not 100% getting it yet, but I'll figure it out.So PWM is the best way. Now is PWM -> mosfet -> capacitor (smooth it out) -> motor ideal do you think?