4qd VTX-75 Buku Petunjuk - Halaman 9

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Speed pot.

We suggest a 10K linear pot, although other values

from 4K7 to 20K, linear or log, can be used.

The gain adjustment on the controller alters the

amount of rotation required before full speed is

reached: this enables a simple lever operated control

by means of a lever arm screwed onto a standard

rotary pot.

The simplest speed control is an ordinary rotary pot:

this won't give any 'dead man' control as the pot

won't return to zero when it is released. 4QD can

supply a spring return to zero hand control.

Alternatively 4QD can supply a plunger operated pot

(linear position sensor), suitable for incorporating

into a foot pedal.

The drawing shows the pot supplied by 4QD

front

With this pot you should only solder to the tips of the

tags: the holes shown are not for soldering but as

heat barriers to stop heat travelling up the tag and

melting the plastic body.

¶ Use as voltage follower

Instead of a pot, the input may be fed from a variable

voltage. 0v (common) to pin F, signal input (+ve) to

pin E. A resistor (10k) should be connected from pin

D to pin F to over-ride the internal pot fault detector

circuit.

Zero speed will be for zero voltage input and full

speed voltage may be adjusted (by the pre-set) to be

from 3v to above 20v. Input impedance is 100K.

If pin D is shorted to pin E (and the 10K present) the

gain control may be used as a pre-set speed control.

Ignition and reverse inputs are both high impedance

(voltage controlled). High activates. Thresholds are

around 5v and 7v.

VTX series instructions

side

back

On/Off switch

Circuitry in the controller switches it off (zero

current consumption) unless there is a voltage on pin

B or pin C.

The wiring is shown on page 6.

Beware of changing any switch when the motor is

running: the motor will brake to a halt more or less

quickly, depending on the deceleration ramp setting.

If the switch changed is the reverse, it will then

accelerate up to speed in the other direction. This

process is quite safe (for the controller).

With the ignition off, or even with the battery

disconnected, the relays short out the motor so free-

wheeling is not possible. To freewheel properly the

motor should be disconnected.

Reversing

Reversing switch

Reversing switch connections are shown in the

diagram above. Reversing is 'dual ramp' which

means that, if the vehicle is reversed at speed, it

automatically slows down under control of the

deceleration ramp then reverses and speeds up under

control of the acceleration ramp.

Whenever the vehicle is in reverse, a speed reduction

circuit operates, so that (if the gain adjustment has

been set up sensibly) full reverse speed is half of full

forward speed.

Reverse Speed reduction

¶ If half speed reverse is not required it can be

disabled by moving the header marked 'HSR' on the

board (and shown in the 'features' diagram). This is

a pinstrip with a shorting link which simply unplugs.

As shown (bottom pin free) reverse is at half speed.

Reverse threshold

If you are reversing the controller from, for instance,

a microcontroller, the threshold is around 5v. A

voltage above this selects reverse, below the

threshold selects forward.

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