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Panda + 2A Motor Sheild + MOSFET = Golf Cart Controller


#1

Hello FEZ users new here but thought I would present to you my plan to upgrade my old resistor type golf cart to a much more user and battery friendly setup. My plan is to use a POT to drive an analogue input based on voltage to set the PWM to drive the 2A motor controller which in turn will drive a high power MOSFET to deliver the needed 36V to the drive motor on the cart. I have my Panda and motor shield on the way and will start small by at first just getting everything working with a small 12V motor and go from there. Any input would be greatly appreciated as this will be my first project based on the NETMF platform I am sure I will have many questions along the way so I look forward to conversing with fellow FEZ users! 8)


#2

How do you plan on isolating the FEZ?


#3

As I said I am new to this but would think the motor shield would isolate the FEZ as the shield will be driving the MOSFET, I may however be mistaken and any input from the great minds on this forum is welcomed. It’s been well over 10 years since I messed around with programming PIC’s (not that the Panda is anything even compairable FEZ looks so easy) but I am interested in getting back into the scene! :wink:


#4

I wonder what the stall current is on those puppies?


#5

I’m not sure that using the motor shield to try and drive a larger mosfet will work. If you don’t get the mosfet turned all the way on or off it will over heat. My point about isolation was that generally when using a uC to control high voltages you want to isolate the uC from the high voltage section so if something goes wrong the uC does not get blown up (or catch fire.)


#6

http://www.pololu.com/catalog/product/1457
I can’t tell from reading this one. Wonder if your logic can be different supply then high volts here or if you need common gnd?


#7

Thanks for all the input guy’s it gives me a lot to think about :o. I did receive my Panda in the mail yesterday and got a small program loaded and running that ramps up and down PWM on an LED ;D 8). Now I am going to look into what code I will need to control that LED with a POT. Any links to some example code would be much appreciated!

Thanks again everyone :wink:


#8

@ budman. Not sure understand. tmk, controlling led current via a pot is no code, just add pot. Are you saying control current via mosfet and gate code?


#9

Sorry should have been more specific, I would like to use the Panda to control the PWM output based on the input from the POT using an AO input. As of last night I have the code set to drive the LED at 50% until I press a button and then it changes the duty from 5% to 95% up and down until I release the button. I basically want to be able to adjust a pot and based on the voltage the uC sees be able to send out a PWM value.

Edit: I am just taking baby steps at first to try to get familiar with NETMF so that is why I am try ing to control the LED. After I get that worked out I will venture into the motor sheild and try to get a small 12V motor to be control by PWM based on the pot value. Then I will have to design some type of circuit that will let me control a high powered mosfet for my golf cart motor.


#10

look for the potentiometer code on fezzer - or the driver from the GHI hardware potentiometer. It’s pretty simple, read the analog in to determine the relative value - then translate this to your PWM duty cycle.


#11

Thanks Brett will do that now, also how would you translate the value to the PWM output in code?


#12

you read a value between 0 and 1023 from an analog input. 0 meaning 0% and 1023 meaning 100%. You then do some maths to work out the percentage and set your PWM duty based on that. Simple huh!