Paul & Sabrina's cheap DIY 144v motor controller

[adamj12b]

Originally Posted by Nevyn

The power board is the same no matter if you have the "regular" control board or the planned SR board, right?

No, the SR board and the regular board need different power boards. The SR board uses more mosfets in place of the diodes.

-Adam

[Nevyn]

That's what I thought. Thanks.

[electrowizard]

Originally Posted by Kasmodean

1) Every controller circuit I have looked at either has a capacitor connected to the motor's + & - terminals, or no capacitor, or capacitors around the + & - terminals and from + terminal to ground. In your schematic you have lots of capacitors from Batt + /Motor + to ground. How does that control the voltage spikes hitting the diodes from the motor - terminal while the mosfets are off? Or if that is not the purpose of them, what it?

Hi Kasmodean;
I've been working on my own controller based on P+S's controller. I have found why the capacitors are needed, and Paul is exactly right:

Originally Posted by MPaulHolmes

You want to keep the inductance as small as possible, so the capacitors, mosfets and diodes need to be really close. If you had no caps, the pulses would have to come from the batteries, which would be far away, and the ESR would be high. The large inductance would cause very large voltage spikes as the current tried to change quickly, which would probably destroy the mosfets.

You can see my controller here: Homebuilt Electric Vehicle, especially the first post's link back to my ecomodder forum post "Why is my diy controller blowing mosfets?"

I have determined that the 3" long by 1" wide 1oz traces between the buss bars and the capacitor bank has too much inductance. The mosfets have such a low impedance and such a fast turn-on time that the voltage across the B+ and B- rails goes crazy. Measured with an oscilloscope across the rails, the nominal 12V potential oscillates between 0V and 24V at 25MHz.

So when people tell you that layout is important, they *really* mean it.
I thought I could get away with it by making a very short controller, and building on buss bars which should have lower inductance than building on copper PCB. However I learned that you CANNOT get away with bad layout, not for serious currents

I still need to rethink my design; I'm hoping that adding small axial capacitors directly to the mosfet drain and B+ will allow me to continue without scrapping all my work. Just letting you know to be careful!

-William

p.s. you can get away with the bad layout for small currents. My controller is currently built to handle 120A continuous and several hundred intermittently.
Despite the poor layout and the oscillations, my controller works perfectly on a 14A car window motor. The problem is it blows up if I use a car starter motor :P

[Nevyn]

I got some stuff up in the Wiki - parts list for SR3 board. Feel free to add, edit, update if it's wrong. Paul, I took it from the parts list you sent me; but the info was pretty sparse.

[Grimm]

I'm keeping my eye on this little box as it looks like a perfect companion to the controller as well as other diy projects (arduino)

It has decent specs, tiny enough to fit in a glove box, fanless, and has two powered COM ports!

MSI Global ? Computer, Laptop, Notebook, Desktop, Mainboard, Graphics and more

[thingstodo]

Hi everyone. First post by a newbie.

I started yesterday and went through the first 100 pages of postings, and then the last 50 or so. I have some of the history but not all. As someone commented, its like trying to drink from a firehose.

Great job everyone on contributing your expertise (ideas, testing, building, documenting) to promote the common good!

Although the system is open source and DIY, it is far from amateur. I've been a controls engineer for many years (almost 25? Yeesh I'm getting old) and I've torn down many boards from many vendors when they stop working. Few are as well laid out, with as much attention to detail, as your project is. If the engineers who were paid to design those electronics had the pride and perseverance that you do, the boards would not have failed in the first place. Your feedback system, where many people with differing experience levels take a crack at each step, IMHO, is how engineering is supposed to be. Design, build, test, discover, repeat.

I'm going to check out the 3 phase project, the BMS, and the charger.

[princeton]

I'm new to the thread. I've been trying to work on a controller at home but after reading this thread, mine seems way too simple. Why does it have to be this complicated? Are all the features that necessary?

[MPaulHolmes]

No. hahaha. It can be extremely simple. Check out Ian's Speedy controller. I wanted to write all of Joe's stuff, but it would have taken too long. hehe. See below. Go Joe!

[jyanof]

Originally Posted by princeton

I'm new to the thread. I've been trying to work on a controller at home but after reading this thread, mine seems way too simple. Why does it have to be this complicated? Are all the features that necessary?

Some hardware features that add complexity and what value they add (IMO):

1. hardware overcurrent protection: saves the power section while testing out new software. one wrong line of code could command the controller to fully turn on unregulated and blow things up (or result in a runaway car).

2. serial output: nice to help troubleshoot software by looking at the output so you know what the controller is doing. also allows an easy way of updating software, changing controller settings, and add-on software (see adam's RTDexplorer).

3. Opto isolation: this is pretty important. it allows the high current power section to operate without any electrical link to the control board. This greatly reduces noise that could screw up the micro or ADC conversions or whatever.

4. power section undervotlage protection: keeps the mosfets from turning on if the gate-driving-voltage is too low (from the output of the DCDC converter). If they only turn partway on, they'd heat up quickly and result in a blown powersection and possibly a runaway vehicle.

5. thermal protection: in the right setup and driving style, it won't be necessary. but, just in case, it'd be a shame if the controller blew up (possibly resulting in a runaway vehicle) because it overheated and didn't automatically reduce output power.

6. current sensing: this probably should have been first. it's way too easy to get ridiculously high currents in an EV motor. the output current must be regulated through some sort of feedback system.

hm, are there other hardware features? there's a ton of software features that aren't really necessary, but are nice to have. writing code is free, though.

[princeton]

Has anybody tested their controller with 20KHZ, full amperage or are they sticking with 4 khz for testing?