Saturday, 22 January 2011

Chapter 5, Buying the controller

I have just ordered a kit for building the cougar controller!

First of all I would like to explain how a controller works to all those watching, who are not in familiar with the components in an electric car:

In an electric car the controller is the component which adjusts the speed of the car as mentioned in chapter 4 (about the potbox) In a DC electric car, such as my own it does so by adjusting the voltage.

Back in the old days, adjusting the voltage to control an electric motor was done with big resistors, the resistors were then bypassed by a switch one after one when you wanted to increase the power and speed of the motor.
However this was highly inefficient as the resistors would just burn of all the power that would otherwise been used in the motor! Kind of like controlling a combustion motor by opening a hole in the fuel connection and just burning off the excess fuel when you want the motor to slow down.

Because this was highly inefficient the old trams back then also tried, as much as possible, to avoid using this to control their speed.
If you notice it there are a lot of wires sticking out of their traction motors, this was because they could also choose only to turn on parts of their motor at a time so that they could control the speed in a such way.

Luckily new technologies came along, so I do nether need big power consuming resistors nor a complicated motor.

This is how it is done today: Full voltage is fed into a modern controller it turns the voltage by switching the power on and off in a series of rapid pulses typically above 15000 times in a second depending on how much it is left on the ON position or the OFF position the voltage "changes" and thereby the speed and power of the motor can be controlled.
The Cougar Controller:

The Cougar controller unlike others on the market is an open source controller, which means that the plans are free on the net so you can build it your self out of parts you find, or you can (as I did) buy a complete kit from Paul ( ) The person who developed the open source controller.
Open source projects also allows people to improve on the design along the way

Usually I recommended to go for factory stuff when building an electric car. This is because of safety reasons. It is easier to test and certify components build in a large quantity than the fledglings of armatures.

However in this case this particular controller has various safety features that is comparable to the ones at a commercial controller.
see under "EV DC Motor Controller "Cougar" Features"

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