Temp based pump controller

Forum 2005-2010 (read only) Hardware Interfacing
#1

Hi guys, I'm trying to interface a pump that will be controlled via the PID library and a temp probe.

The pump details are as follows;

MOTOR 12V Brushless OPERATING VOLTAGE 9V DC to 15V DC MAX CURRENT 1.3 Amps FLOWRATE @ 10 kpa 15 L/min (4 gal / min) OPERATING TEMP -40° to 120° DegC PUMP DESIGN Recirculating Centrifugal

So I figure I will need something like the following;

Would something like a NPN TIP31A be suitable ?

Does the design look sane ? this is pretty much my first Arduino project.

#2

Should there be a link that has gone missing?

I think at over 1A I would use a logic level FET rather than a transistor.

#3

Did the image not show for you ?

I made it available here;

http://i378.photobucket.com/albums/oo224/nalberti/Temp_controller.jpg

So like an N-Channel MOSFET ? like an IRF510 ?

#4

like an IRF510

Like yes, but not an actual IRF510, because it won't turn on properly if connected directly to an Arduino. You need a logic level MOSFET.

#5

Ahh.. yes :)

IRL510 ?

#6

Did the image not show for you ?

No it doesn't, thanks for the link. In general this is the way to do it but as I said you need a FET because a transistor would get too hot.

Don't forget to connect all grounds together and if you use a FET you don't need the series resistor.

See this link what you need is almost the same:- http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1241963534

#7

Thanks for the link :)

Updated diagram.

http://i378.photobucket.com/albums/oo224/nalberti/Temp_controller-1.jpg

#8

Looks OK to me.

#9

Would this work with a brushless motor ??

#10

Yeah, I was a bit confused by that “brushless” part too. Did you hook up 12V to the motor just to try it at some point? If it just started turning then it’s not brushless and your circuit should be OK (except I would add some series resistance to the gate if the ATmega168 board doesn’t already have some to limit current from the ATmega168 pin).

If the motor doesn’t turn with 12V directly applied to its terminals…you have a slightly more complicated problem on your hands.

#11

The pump is a sealed bearing magnetic drive, supply is a 2 wire 9-15Vdc.

#12

Another question :)

I am considering adding thermatic fan control to the circuit, easy enough, my question is regarding the best way to switch the fan.

The fans I am looking at are 5A@12VDC, Typically they are controlled via a standard automotive relay, I would like to avoid having two components and just wire them in directly in some fashion.

Would an optocoupler, solid state relay or transistor be a potential option or am I just better off with a plain old relay ?

#13

Again a logic level MOSFET is the simplest method. Just make sure it’s rated for the total current of the attached loads and research if and how big a heat sink you may need for the MOSFET.

One thing I would recommend when using a MOSFET that switches a voltage that is other then the internal Arduino 5vdc or Vin pins and that is to add a resistor from the MOSFET gate to ground, 10K ohm should be fine. A ‘floating’ MOSFET gate can cause problems in some cases. This will insure that the MOSFET will stay off if you power down the Arduino without powering down the higher switched voltage that the MOSFET is controlling. Otherwise it’s possible for the switched device, say a motor will turn on until the Arduino is powered up and sets it’s I/O pin to output mode and low output. That make sense?

Lefty

#14

Here is my understanding of what you suggest;

http://i378.photobucket.com/albums/oo224/nalberti/Temp_controller1.jpg

#15