4QD Motor Speed Controller features
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Voltage Following

This page is a little more technical and may safely be skipped!

All controllers made by 4QD work with a voltage input, normally derived from a pot (potentiometer). However it's the voltage input that determines the speed. The controller cannot tell whether that voltage is coming from a pot or a 'black box'. So you can feed them from a microcontroller or other electronic 'gizmo'.

This voltage is adjustable by the gain preset. Typically you need a minimum of 0-3v but you can use 0-10v or 0-almost anything! Simply adjust the controllers's internal gain preset to suit.

In the case of a feed from a microcontroller, you'll normally be using a PWM output and adjusting the PWM duty cycle. The controller will react to the PWM's average voltage as if it was a straight d.c. voltage.

If the frequency of the PWM signal is too low, then you will get a modulated signal through to the motor but this is not often a problem.

Since all controllers include pot fault detection, you will need to connect a resistor in place of the pot, to stop this feature engaging.

With the Uni controller, the pot fault detection needs to be deactivated. There is a note about this in the instruction manual, available from the manuals section of our site

There's more information in our FAQ sheet, under voltage control and under Digital control

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