I would suggest using this PID library: https://github.com/br3ttb/Arduino-PID-Library/.
You could then pass a desired speed via serial, and use that for the "Setpoint" variable.
For measuring the speed with an optical encoder, you could connect that to one of your external interrupt pins, and write an interrupt routine, that increases a variable by one on every interrupt, then calculate your speed in the main loop, there are a lot examples on this forum for this.
If you get stuck on specific issues, there is probably help available here.

Hello SebClerckx, that sounds like a great project. Is it intended for use with brushless DC motors, and if so, do you plan plan for sensorless or sensored feedback? Also, when it is for use with Arduino, I think it would great to have as many feedbacks to Arduino as possible, so in addition to current sensing; voltage, rpm and temperature would be great. I’m sorry I can’t give any technical advise, as I’m untrained in electronics and programming, but I’ll be following with interest. It seems to me that members of this forum is very generous in answering questions, especially if you keep it specific, and backed up with schematics, datasheets etc.
Good luck with your project!
Peter

I bought the Allegro sensors on ”breakout” boards with large double sided conductive path (looks gold-plated, not sure about that though) with 6mm bolt holes. I can´t find them on eBay anymore, so i don’t have a link. As I already have them, I’ll try them out, but if it proofs too inefficient, I’ll give you a call Docedison, thanks.

The motors are replacing a 13hp ice motor (maybe the right term is ride-on lawnmower rather than tractor). So about 4 hp for drive, which I think is more than enough, and about 4 hp for the blades which might be too little, but if it works I’ll probably be happy to cut the grass before it gets to long. With this setup, I can also eliminate some pulleys and the clutch, which hopefully will reduce the power requirements a bit. I’m going to use four 85ah marine batteries, and I’m hoping to get a couple of hours juice for just driving, and maybe 40 minutes of grass cutting.

The Arduino will try do reduce power to 130 amps per motor, and will allow 150-200 amps for max 5 seconds, and will shut of power completely if consumption is more than 200 amps for one of the motors. The Arduino also handles speed control, rpm-safety-shutdown, general safety, voltage monitoring, battery protection etc., but more on that when my code fails, and I´ll be looking for help in the programming sector

I bought an small electric forklift a while back for a different project, and the drive motor seems very similar in size and weight to the motors I'm going to use. It’s also 24 volts and series wound, but there no dataplate, so i cant be sure about the specs. I think it’s popular to use series wound motors for forklift, because its easy to reverse rotation by reversing power to either the stator or the rotor?

The motor is 133 amp 24 volt series wound dc. I don´t know what they where intended for (maybe forklift), but i managed to get hold of 6 of them, maybe 10 years old, but unused. I´m converting a lawn tractor to electric with a motor for drive, and a motor for grass cutters. Arduino is at the heart of the operation. I promise to make a ”bragging” post when the project is finished

There is little risk of personal injury, as the system is only 24 volts. But I see your points about troubleshooting and also it makes sense to not have permanent power on ground leads. I will have to find the best compromise between physical layout, possible interference and safety. Thank you.

Thank You, I thought so, but it's nice to be sure. I'll probably need to read up on my electrical basics

Current measurement on positive or negative side?

Hi,
I´m going to use this sensor: ACS758ECB-200U-PFF-T (http://www.allegromicro.com/~/Media/Files/Datasheets/ACS758-Datasheet.ashx), and I was wondering if it makes any difference if I place the sensor on the positive or negative side of my motor (130 amp dc). If I could place on the negative side, it would allow for much shorter sensor wires. Thanks
Planned setup is: Battery positive --- motor --- current sensor --- contactor --- mosfets --- battery ground

Yes, the 4 pins fit in a breadboard, it needs 5v, ground, tx and rx.

Hello,
I use this bluetooth modul: http://www.ebay.co.uk/itm/9600bps-Bluetooth-Module-Slave-Wireless-Serial-Port-f-Arduino-Self-Balance-Robot-/320811073537?pt=UK_Sound_Vision_Other&hash=item4ab1d48001 with Amarino, Arduino Uno and HTC Desire, I've never had any problems. Hope it helps

Thank you all very much for your suggestions and advice. I’m sure more questions will arise, when I start building

Hi dc42, Thank you very much for your reply, its very helpful!

The 100 ohm resistors, are for protecting the input pins, in case they are accidentally configures as outputs, but it seems a bit “clumsy”, and I’ll go for the more usual approach with pullup resistors. 

I already have the IRL1404 mosfets, so I’ll probably try my luck with them. I’ll be using some very large heatsinks scavenged from an electric forklift.

Setting the PWM frequency to about 20 khz should be possible for timer1, but I’ll have to read up on that. There are already a couple of threads on this forum on the subject, but it’s hard to understand.

I’m now thinking of using these for flyback diodes: http://www.sanrex.com/images/PDFs/BKR400AB10.pdf , but I can’t make out if they are fast enough. Would it be a good choice? Or can anyone suggest an appropriate diode?

I have some more questions regarding noise suppression.

What kind of capacitors should I use for motor noise suppression?
I’m planning of using the mower chassis for common ground (like most cars). Is that a bad idea?

Hi o_lampe, thank you for your reply.

I didn’t plan on using capacitors in the high current circuits for the motors, maybe I should? Anyway, without capacitors, the precharge resistors are probably redundant, thanks for pointing that out. I’ve got a small delay in my code to make sure that the contactors are closed before the motors are started, so hopefully, that will take care of sparking.

The safety-switch is actually the “seatswitch”. I’ve also programmed for a “soft throttle response”, and the mower is going to be quite heavy, so I don’t foresee any wheelies, although the redneck in me kind of wished I could pull a wheely on a lawnmower 

Also my code makes sure that the mower can’t be activated if the throttle is pressed at startup.

All input switches are taken care of by the “Android user-interface”. I’ve attached a picture below.

Where I am in most doubt is regarding the mosfets and mosfetdriver I’ve chosen, my mosfet-circuit, sizing of flyback diode (I’m now thinking of using these http://www.diodes.com/datasheets/ds31413.pdf, as I already have two of them for another project) and noise suppression capacitors. Does anybody have any input/suggestions on this? I would like to avoid buying commercial motor controllers, if at all possible.

Thank you for your reply kf2qd. I have mechanical reverse, so only one motor-direction is needed. The commercial controllers I have found, that are capable of the current needed, are too expensive for me, so I would like to take my changes with my simple mosfet circuit, if at all possible.
I have manipulated timer1 for PWM frequency of 31khz.
Would a 20A 100V SCHOTTKY DIODE be a good choice for flyback protection instead of 1N4004?

Hello All,
I’m doing a ride-on mower electric conversion for a fun winter project. An Arduino is going to be the brains of the system. I have no background in electronics or programming (so please excuse my non-technical English), which makes this project quite challenging. Basically I’ve been googling a lot, and from that trying to implement other peoples experiences in my project. My lack of knowledge makes me expect a lot of confusion, headaches and smoke, but I’m hoping to minimize the smoke, with some help from you guys.

Description and schematics below.

Here is where I need your help:
1.   Is the mosfets I’ve chosen good enough? (They will be mounted to large heatsinks with fans. The stall current of motors is unknown, but my code will shutdown power to each motor if current is more than 200A or if current is more than 130A for more than 5 sec. I plan to use PWM frequency of 31khz)
2.   Can I use a single mosfet driver for driving 5 mosfets in parallel? And is my driver chip up to the job?
3.   Can I use 0.1uf small ceramic disc capacitors for noise suppression on such a large motor? (I have copied what others have used for much smaller motors, not being able to find examples for high current motors)
4.   Do you see anything in my circuit that will cause smoke, simply not work or is redundant?

Any input is greatly appreciated 

The project:
Ride-on mower with one motor for drive (mechanical gearbox, so only one direction speed control is needed) and one motor for blades/cutter-deck. Arduino will be controlling speed of motors and monitoring voltage, drive-motor current, blade-motor current, system current, rpm for motors, safety switch, brakes (mechanical brakes) and “reverse-selected”. User interface will be an Android phone communicating by Bluetooth with Arduino.

Progress:
I have written the code for Arduino and Android and it works with simulated sensor values. Almost all parts have been bought, and next step is assembly.

Important parts:
Arduino Uno R3

Motors: 24V, 130A continuous, 2600 rpm, series-wound DC (unknown: stall current)

Batteries: 4pcs. Marine deep cycle 12V 75ah, flooded type (connected for 24V)

Mosfets: 5 pcs. IRL 1404 in parallel for each motor. Datasheet: http://www.irf.com/product-info/datasheets/data/irl1404.pdf

Mosfet Driver: TC4422, one for each bank of mosfets. Datasheet: http://ww1.microchip.com/downloads/en/devicedoc/21420d.pdf

Power supply for each mosfet driver: http://www.ebay.co.uk/itm/130680030803?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

12V supply for Arduino, lights etc.: http://www.ebay.co.uk/itm/24V-to-12V-DC-DC-Car-Power-Supply-Converter-30A-New-/180743402619?pt=LH_DefaultDomain_3&hash=item2a1525747b

5V supply: http://www.ebay.co.uk/itm/UBEC-5A-8-26v-SBEC-Switching-BEC-Lipo-UK-Sale-/330792884209?pt=UK_ToysGames_RadioControlled_JN&hash=item4d04cad7f1

Current Sensors (200A each): http://www.ebay.co.uk/itm/110894073072?var=410115820134&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Hall Sensors: http://www.ebay.co.uk/itm/Hall-Sensor-Module-for-Magnetic-Field-Detecting-0-15V-/320748421434?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item4aae18813a

Relays for lights, reversing light, horn and contactors: http://arduino-direct.com/sunshop/index.php?l=product_detail&p=156