Peristaltic Pump Setup
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Peristaltic Pump Setup

by mrmu on Mon Feb 25, 2013 3:03 pm

Hi,

I'd like to purchase this pump:
https://www.adafruit.com/products/1150

Can someone let me know what else I will need to get it hooked into my Arduino and running properly?

Thanks,
Greg
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Re: Peristaltic Pump Setup

by adafruit_support_bill on Mon Feb 25, 2013 3:14 pm

To pump forward and reverse you will need an H-bridge, such as the ones on the Motor Shield. http://www.adafruit.com/products/81
If you only need to pump in one direction, you can drive it with one of these. http://www.adafruit.com/products/355
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Re: Peristaltic Pump Setup

by mrmu on Mon Feb 25, 2013 3:38 pm

Thanks! I only need to pump in one direction so I will get the N-Channel.

Is there any type of tutorial to wire up the peristaltic pump with the N-Channel and Arduino?
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Re: Peristaltic Pump Setup

by mrmu on Mon Feb 25, 2013 3:42 pm

Also for this Brass Liquid Solenoid Valve - http://www.adafruit.com/products/996

It mentions that you need one of these diodes along with the N-channel: http://www.adafruit.com/products/755

Will I need this for the peristaltic pump?
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Re: Peristaltic Pump Setup

by adafruit_support_bill on Mon Feb 25, 2013 6:23 pm

Here is a wiring diagram - including a kickback diode:
Attachments
mosfet.png
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Re: Peristaltic Pump Setup

by mrmu on Tue Feb 26, 2013 12:36 am

Thanks, where does the 12V wire go? I thought I would be able to connect it to the voltage pin on the Arduino through the N-channel.
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Re: Peristaltic Pump Setup

by adafruit_support_bill on Tue Feb 26, 2013 7:35 am

You can connect it to the VIN pin on the arduino. Or you can use a separate 12v supply and connect the ground from that to the ground on the Arduino.

I drew it as a separate supply for 2 reasons:

1) DC motor brush noise from the pump can feed back into the system and cause erratic behavior of the Arduino. A separate supply provides some isolation from this.
2) Although the Arduino is rated to take 7-12v DC input, the 7805 regulator on the board runs pretty hot when on 12v. I don't like running them on more than 9v.
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Re: Peristaltic Pump Setup

by mrmu on Thu Feb 28, 2013 2:16 pm

Wow, awesome response! Thank you very much

While we are at it, I've had some pieces for another peristaltic pump printed out and I need to get the rest of the parts. Could you direct me to equivalents of what you have related to this list?

http://peristalsis.tentacleriot.eu/

Here is the spec for the pump:
http://www.thingiverse.com/thing:8914
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Re: Peristaltic Pump Setup

by adafruit_support_bill on Thu Feb 28, 2013 3:36 pm

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Re: Peristaltic Pump Setup

by mrmu on Wed Mar 06, 2013 3:24 pm

Hi, I got my peristaltic pump.

I'm a noob to this. Can you tell me which of the 2 metal prongs at the bottom of the pump I connect voltage to and which one I connect the wire that I connect to the N-channel?

Thanks
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Re: Peristaltic Pump Setup

by adafruit_support_bill on Wed Mar 06, 2013 5:28 pm

Don't worry, you won't damage anything connecting it backwards. Connect them either way. If it pumps in the wrong direction, reverse the leads. :D
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Re: Peristaltic Pump Setup

by mrmu on Thu Mar 07, 2013 7:41 pm

Awesome! I got it working, so cool!

Now, I'm wondering 2 things:

1) How do I control the rate of the pump? Can I do this with software or do I need another piece of hardware? I want to do this through software rather than using a potentiometer.

2) How does the MOSFET N-channel 'complete the circuit' that allows the pump to turn on? The way it is wired there is a voltage potential in the pump. The N channel absorbs that voltage, right? Then I'm wondering what exactly happens when the command from the Arduino pin is sent that allows the current to then pass through the N-channel to the ground, thus allowing the pump to turn on.
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Re: Peristaltic Pump Setup

by adafruit_support_mike on Thu Mar 07, 2013 10:38 pm

mrmu wrote:2) How does the MOSFET N-channel 'complete the circuit' that allows the pump to turn on?

Quite nicely, thanks. ;-)

The detailed answer exceeds the Recommended Daily Allowance of Quantum Physics for the average adult, but at a human level, the mosfet is basically a drawbridge for electrons.

Electronics deals with the movement of 'charge', which usually means 'electrons' but can technically be any particle that carries an electrical charge.. in electroplating tanks, the moving charges are actual metal atoms drifting through the liquid.

Voltage is the force that makes charged particles move. The amount of energy available to do work is a combination of how many partices you have and how fast they're moving, and is called 'current'. Obstacles that prevent current from flowing are called 'resistance'. Voltage pushes current through resistance, and when current meets resistance you get voltage. If you know any two, you can work out the third according to Ohm's Law.

Mosfets are made from silicon, which is.. complicated.. all "conductance and valence bands", "localization", "dopants" and the like. The upshot is that you can change the resistance in a piece of silicon by applying voltage to it.

A mosfet is arranged so the resistance is really high (several million ohms) in its natural state, but drops to only a few ohms (or thousandths of an ohm for power mosfets) when you apply voltage to it. Current flows between a mosfet's 'source' and 'drain', and the amount of current that flows between them depends on the voltage at the 'gate'.

So.. when a mosfet's drain-source resistance is high, it's much larger than the resistance of anything else on that path between the battery's positive and negative terminals. We say the mosfet's resistance 'dominates' the behavior of that path. When the mosfet's resistance is low, it's much smaller than the resistances of anything else on that path, so the other compoents dominate the path behavior.


To control the speed of the pump, you use a technique called 'pulse width modulation' or PWM.

Current measures the amount of charge that goes from here to there in a certain amount of time. If you let current flow freely half the time and shut it off completely half the time, the average current over time will only be half what it was if you didn't shut it off.

That principle extends all the way down. If your unimpeded current rate is 1 Amp, but you only open the switch for 1 microsecond per second, the average current per second will be a microamp. Over the long term, the on/off switch acts like a resistor (1 million ohms in this case) but doesn't waste energy as heat like a normal resistor does.

A mosfet makes a good on/off switch, and you can set its effective resistance by changing the relative amounts of on-time and off-time. The part where the switch is open and current can flow is called a 'pulse', and you control ('modulate') the current by changing the width of the pulse.
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Re: Peristaltic Pump Setup

by adafruit_support_bill on Fri Mar 08, 2013 6:04 am

Thanks Mike!
To control the speed of the pump, you use a technique called 'pulse width modulation' or PWM.

On the Arduino, this is most easily done via the analogWrite() function: http://arduino.cc/en/Reference/analogWrite
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Re: Peristaltic Pump Setup

by stocke on Tue Mar 12, 2013 9:34 pm

I purchased this pump, I'm able to get it to operate (the motor turns) but it does not actually pump any liquid .... I purchased two of them so I know its not just a defective one, I snapped off the pump head and it lolls like the only thing that drives the rollers is the motor spindle .... the are no gears its just friction, so the spindle just spins and the pump does not move. How is this supposed to work?
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