M.L. Toys
M.L. Toys
HobbyMasters M.L. Toys
Electronic Scooter Controllers have become a popular addition to our vehicles. Ask specific questions about ESCs here!

***WARNING*** this section is for ADVANCED MODDERS. if you try anything in this section you NEED to expect minor issues with the build up to and including complete FAILURE of EVERYTHING in your freshly built BPRO.

Have fun ;-) :-)
Hi all,

As much time as I've browsed the forums here, this is the first night I've read through the ESC forum.

I designed and built a very very simple basic controller after accidentally blowing up the stock controller in my Razor MX350 over a year ago (wasn't paying attention and hooked up the batteries backwards...) It's a very simple PWM DC motor controller with a 0-5V input compatible with the scooter throttles everybody is using. It does not have LVC, and does not care what voltage it is switching -- so it will work for those of you looking for an 18V ESC.

It should work at 12V too, but you might have to eliminate the 470-ohm resistor. If you do this, I would suggest replacing it with the tiniest fuse you can find (250mA exists) -- I designed the resistor in there in case the supply wires to the throttle got shorted, it would limit the current through the regulators to something sane -- but the drop across it on 12V batteries would probably drop the supply voltage enough to change the oscillator range, meaning the throttle response wouldn't be the same.

The current shunt resistor, R10, is literally a piece of wire. Take everything you know about making sure you have low-resistance wiring, and throw it out the window. You WANT R10 to have some resistance. The 'top' side of R10 will have a voltage proportional to the current flowing through it. That voltage gets amplified to implement the current limit function. R12 and R13 set the current limit: for higher limit, make R12 smaller or R13 bigger. You'll have to get the values by experimentation - because your shunt resistor is part of the formula, and I can't tell you how to get a set value.

D2 is not really a BYV32 - I just couldn't find another device in the eagle libraries that fit. It's a dual rectifier diode in a TO-220 case, you can find them in computer (and other switching) power supplies all the time.

Q2 is any N-channel mosfet. Its ratings determine the controller's rating. Mine is a 60V 80A fet out of an old computer UPS. Aim for a current limit of about half the fet's rating. Mine is thus set for 40A. Of course you can set it lower to protect your motors.

Do not attempt to run this circuit over 24V. The input limit for the 7812 is 30V. 24V batteries can go up to 28.8V worst-case. Another battery would push it over the limit in any case. I have since built another controller of similar design that allows higher voltage use (up to 96V) but I'm not posting that until I've run it long enough to be confident it's not going to grenade.

I've been running this one for over a year, daily, in an MX350 with no problems -- I use it a lot for trips around town, and tend to go through two 24V 7AH charges a day.

If you choose to build this, you do so at your own risk. This controller doesn't have any misbehaviors or failure modes that aren't common to every other pwm dc motor controller out there, but most of the commercial offerings have backup protection/failsafe circuits to mitigate them. This is barebones, raw, and very basic. Q2 needs a heatsink. If it runs too hot, it will eventually fail. They usually fail short, which means 100% output. That's how all controllers fail, except some of them have a relay to shut it off it that happens. You implement your own protective circuits. Use a brake relay, and provide a manual power off switch. These are things that should be common sense on any build anyway, no matter what controller you use.

As I said, it was originally built to replace an MX350 controller. I reused the stock case and heatsink, so Q2 and D2 were placed in the original spots (to line up with the stock heatsink) and the rest of the board layout was built around that.
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Last edited by emolatur on Fri Nov 27, 2015 2:58 am, edited 1 time in total.
:shock: :shock: :shock:
Very cool. I probably parts in my bin to make one. However, by the time I transfer and etch that PCB $12 for a 24V 500W controller sounds more appealing. Don't get me wrong I am a DIYer but... I have to concede sometimes.
I used the pad-per-hole grid board. Some companies call it "perfboard," others "veroboard," whatever it is, it was four bucks at Radio Shack. The rest of the parts were scrapped out of my heap of broken stuff. It's not for everyone, but if the situation is right, here it is.

and, actually, I posted it because it doesn't seem like there's a popular 18V solution, and a lot of people seemed to ask.

MY PERSONAL reason for building it? Instant gratification - didn't want to wait for shipping!
No doubt! Always an accomplishment building yourself! Easiest 18v solution with typical esc is to simply use a pot on the throttle wire.
Last edited by sall on Wed Dec 02, 2015 8:12 am, edited 1 time in total.
sall wrote:No doubt! Always an accomplishment building yourself! Easiest 18v solution with typical esc is to simply use a pot on the throttle wire.

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