Arduino driving a 12 volt 10 amp motor

I have an automotive project I'm working on and have the need to drive a 12 volt 10 amp motor. It's a progressive controller for water/methanol injection on a turbo'd motor. What I'm attempting to do is read the output of the MAP sensor (0-5 volts) and then based on the amount of boost the engine is seeing spray accordingly.
So for example around 10 lbs of boost it kicks on and starts spraying and as boost increases so should the water/methanol accordingly.

I did some googling and found this link that says it's as easy as putting in a MOSFET and driving the motor

Is it really that simple? I single component is all I need? Seems to easy to be true. I mean why do motor shields for the Arduino that drive 2 amp motors have an entire circuit board full of components?

And if that is really all I need can someone recommend an equivalent MOSFET I can purchase locally or online in the US?

Thanks for any input
Malcolm

MalcolmV8:
I have an automotive project I'm working on and have the need to drive a 12 volt 10 amp motor. It's a progressive controller for water/methanol injection on a turbo'd motor. What I'm attempting to do is read the output of the MAP sensor (0-5 volts) and then based on the amount of boost the engine is seeing spray accordingly.
So for example around 10 lbs of boost it kicks on and starts spraying and as boost increases so should the water/methanol accordingly.

I did some googling and found this link that says it's as easy as putting in a MOSFET and driving the motor

http://www.hobbytronics.co.uk/arduino-tutorial9-power

Is it really that simple? I single component is all I need? Seems to easy to be true. I mean why do motor shields for the Arduino that drive 2 amp motors have an entire circuit board full of components?

That's because your single mosfet example is only capable of on, off, or variable speed in one direction only. Most motor shields have full H-drive outputs, meaning that both rotation of direction as well as speed is controllable. Also many of the motor shields support two independent motors. So apples to oranges and all that.

Lefty

And if that is really all I need can someone recommend an equivalent MOSFET I can purchase locally or online in the US?

Thanks for any input
Malcolm

Thanks Lefty. It seems you really know MOSFETs. I found this old thread of yours that has a good explanation in it too.

http://arduino.cc/forum/index.php/topic,11565.0.html

Since all I want to do is drive a single motor in a single direction and speed it up and down then the single mosfet design works for me. That old thread of yours speaks about the pull down resister and safety diode as well. Excellent tips.

Now I just need to find a suitable MOSFET and I think I'm in good shape.

MalcolmV8:
Thanks Lefty. It seems you really know MOSFETs. I found this old thread of yours that has a good explanation in it too.

http://arduino.cc/forum/index.php/topic,11565.0.html

Since all I want to do is drive a single motor in a single direction and speed it up and down then the single mosfet design works for me. That old thread of yours speaks about the pull down resister and safety diode as well. Excellent tips.

Now I just need to find a suitable MOSFET and I think I'm in good shape.

10 amps is a pretty heavy load so you may need to consider heatsinking the mosfet for best long term reliability especially in a automotive applications. SparkFun has a nice device, but you might be able to find a even better one with a lower Ron specification, a key parameter after the operating voltage and continuous current ratings. Sometime people recommend running two mosfets in parallel for higher current loads to help spread the heat dissipation across two devices, but then that doubles the gate capacitance and all that effects which could lead to needing to use gate driver ICs, which is also a good way to go for higher power mosfets.

N-Channel MOSFET 60V 30A - COM-10213 - SparkFun Electronics?
SparkFun MOSFET Power Control Kit - COM-10256 - SparkFun Electronics?

Lefty

Thanks for the links. I agree a heat sink will be in order. I'll do some more searching tomorrow and see what other MOSFETs I find.

What about a speed controller like one of these: Radio Control Planes, Drones, Cars, FPV, Quadcopters and more - Hobbyking

They can do the trick. Just connect them to the board and control it like a servo. Very easy and cheap too.

Most of the three phase electronic speed controls will drive a brushed motor connected to just one of the phases.
You can also get speed control for brushed motors, like this one for example: http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXKYN2&P=7

LCCinSpace:
Most of the three phase electronic speed controls will drive a brushed motor connected to just one of the phases.
You can also get speed control for brushed motors, like this one for example: http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXKYN2&P=7

I was in the R/C electric hobby for quite a while and I never heard that you could run a brushed motor on a brushless ESC, do you have link or datasheet showing that usage from any ESC manufacture?

I do see that hobby king does list a few of their ESCs that are specificly for brushed DC motors only. Much nicer prices also.

Lefty

Have a look at fig 7 & 8 http://www.teamtekin.com/manuals/RSManual.pdf

I would think you can do the trick with any brushless ESC - connect the brushed motor between any two of the three wires. If the ESC is intelligent it may check for faulty motors or connections. This may be avoided by inserting two resistors between the unused wire ante the two others.

Anyway, the ESC''s from Hobbyking are dirt cheap - a test would not cost a fortune :slight_smile:

retrolefty:
I do see that hobby king does list a few of their ESCs that are specificly for brushed DC motors only. Much nicer prices also.
Radio Control Planes, Drones, Cars, FPV, Quadcopters and more - Hobbyking

So what's the advantage of purchasing an $8 ESC Vs a $1 MOSFET? Will that ESC work better? or just make it easier not having to get a heat sink?

It depends on your level of electronic skills -and what other components you have on stock. The biggest advantage is probably time. The ESC give you a PWM regulation of your motor that works and is easily controlable from your board.
If time is not an issue then go for the 1$ FET. PWM will eliminate the need for a big heatsink.

LCCinSpace:
It depends on your level of electronic skills -and what other components you have on stock. The biggest advantage is probably time. The ESC give you a PWM regulation of your motor that works and is easily controlable from your board.
If time is not an issue then go for the 1$ FET. PWM will eliminate the need for a big heatsink.

Oh ok. Well from what I can tell the MOSFET is pretty simple too. Since I really like learning and playing with this stuff I think I'll try both routes and play around and see how each one works. Thanks everyone for all the feedback and help.

retrolefty:
I do see that hobby king does list a few of their ESCs that are specificly for brushed DC motors only. Much nicer prices also.
Radio Control Planes, Drones, Cars, FPV, Quadcopters and more - Hobbyking

I purchased one of those controllers to see how it works out (still waiting on it to arrive). After I purchased it I noticed in the pic if you look closely it says 6 volts to 12.6 volts which is roughly the voltage of 3 lipo cells fully charged. In an automotive application the unit is bound to see as much as 14.2 volts or so when the engine is running and the alternator going. Does anybody know how much tolerance these units have for over voltage? I'm wondering if it's going to just burn up. May put me back to my original mosfet design.

" In an automotive application the unit is bound to see as much as 14.2 volts or so when the engine is running and the alternator going. Does anybody know how much tolerance these units have for over voltage? I'm wondering if it's going to just burn up. May put me back to my original mosfet design."

MalcolmV8, I am 1000% noob to Arduino, but Auto 12V, well lets say I grew up in a Automotive shop. All you will need is a ignition ballast resistor for a mid 70's Dodge/Chrysler. A few bucks only. The ignition points in these cars worked on 6-8VDC and the coils did not have build in resistance. Very easy problem to fix. Good luck.

dougski:
" In an automotive application the unit is bound to see as much as 14.2 volts or so when the engine is running and the alternator going. Does anybody know how much tolerance these units have for over voltage? I'm wondering if it's going to just burn up. May put me back to my original mosfet design."

MalcolmV8, I am 1000% noob to Arduino, but Auto 12V, well lets say I grew up in a Automotive shop. All you will need is a ignition ballast resistor for a mid 70's Dodge/Chrysler. A few bucks only. The ignition points in these cars worked on 6-8VDC and the coils did not have build in resistance. Very easy problem to fix. Good luck.

If I put a big resister inline then my water/meth injection pump would be on 6-8 volts too and reduce performance to non satisfactory results.

Look in your drawer for a couple of diodes or more (12amp?) Connect them in series with one of the ESC supply leads. You have between 0.6 to 1V voltagedrop across each diode.

MalcolmV8
"If I put a big resister inline then my water/meth injection pump would be on 6-8 volts too and reduce performance to non satisfactory results."

LCCinSpace
"Look in your drawer for a couple of diodes or more (12amp?) Connect them in series with one of the ESC supply leads. You have between 0.6 to 1V voltagedrop across each diode."

MalcolmV8
LCCinspace is correct in his solution, but I like to run voltages electronics in the middle of their spec band. This helps to reduce heat and increased longevity of the electronics. Now the ballast resistor that I told you about is a very stable simple cheap device. Now in my opinion you have to get some sort of a motor driven rheostat and connected to the analog side of your board. I do believe this would give you the best solution of increasing or decreasing the amount of water/meth you are looking for. This way you could power the motorized rheostat with the full power of the charging system. Just an idea keep in mind I do tend to complicate things a bit. Have a good day.

I think my best solution is just a simple MOSFET capable of handling the voltages at hand. Using resistors or diodes to reduce the voltage so that I can use that brushed speed controller from hobby king also reduces the voltage to the water/meth pump and in turn reduces it's performance. That is an undesirable side affect of going that route.