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Aero Naut Multi 20 Operating Instructions

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Operating instructions

Speed controller for multi-function models

Multi 20 Multi 40

Order No. 7019/71 Order No. 7019/72

Dear customer,

In purchasing the aero-naut Multi 20 or Multi 40 you have acquired a modern, micro-controller based digital speed controller (not

governor). The Multi 20 version features a BEC system (5V power supply for the receiving system). With a maximum output of 1.5 A this

can be used with 6 to 10 (12) NiCd or NiMH cells or a 12V lead-acid battery within the following limits:

Up to 8 cells: max. 4 small servos or 3 larger servos

Up to 10 cells: max. 3 small servos or 2 larger servos

12 cells: max. 2 small servos

If you wish to use a drive battery with a higher cell count you will need to provide a separate receiver power supply, otherwise there is a

danger that the excessive input voltage will overload the integral 5V voltage regulator. In this case disconnect and insulate the positive

pin at the receiver connector, or cut through the red wire at a convenient point.

The Multi 40 always requires a separate receiver battery. In this version the receiver input is galvanically isolated by an opto-coupler.

Be sure to maintain correct polarity of the battery leads (red = +, black = -)!

The motor power leads are yellow and blue, and can be swapped over at the motor terminals to reverse the motor’s direction of rotation.

The controller generates positive voltage at the yellow wire when the channel signal is long (i.e. >1.5 ms). The motor should be

connected in such a way that this corresponds to the forward direction of running.

Programming

If the Multi 20 / Multi 40 is to work perfectly with your RC system it must first be programmed. This process only needs to be carried out

once; the controller stores the settings permanently, or until it is re-programmed.

1. Turn the speed controller over, so that you can see the integral LED. Fit the jumper (bridging plug) on the pins marked >Prog<.

Caution: the controller is supplied with the jumper fitted on the >Prog< pins as standard.

2. Connect the 3-core lead to the appropriate receiver output.

3. Move the throttle stick on the RC transmitter to the neutral (Stop) position.

4. Switch on the transmitter. Multi 40: now switch on the receiver.

5. Connect the speed controller to the drive battery with correct polarity.

6. Wait until the LED flashes once.

7. Move the throttle stick to “full throttle forward” and wait until the LED flashes twice.

8. Now move the stick back to neutral, and watch the LED flash three times. The Multi has now stored the stick travels. “Full throttle

reverse” is always stored as a mirror image of “full throttle forward”.

9. The last stage is to program the power-off voltage, i.e. the point at which the controller throttles back or stops the motor in order to

prevent damage to the drive battery (see battery monitor). This value varies according to the battery type. If you are using a NiCd

or NiMH battery move the stick to around “half throttle forward”; for a lead-acid battery move it to “full throttle forward”.. The

controller confirms the setting with four flashes (Ni-) or 5 flashes (lead-acid). If incorrect, you can correct the setting again

immediately. Finally move the stick back to the Stop position.

10. This completes the programming process, and the Multi 20 / 40 is ready for use. Wait until the LED starts to flash continuously,

then disconnect the drive battery. Don’t forget to remove the jumper.

Brake options

The Multi 20 / 40 features a brake function which can be programmed to two different modes of operation. They are selected by means

of a jumper.

Free-wheel mode

If the jumper is fitted to the pins marked EMK, the power stage works in 2-quadrant mode. The motor is fed pulses of varying length

corresponding to the throttle stick position. The pulse frequency is 16 KHz, and is therefore inaudible. At neutral, and between the

individual pulses, the motor is “free-wheeling”. The proportional EMF brake only takes effect when the throttle stick is moved past the

neutral point in the opposite direction. At this point the Brake Light socket becomes active. In free-wheel mode it is not possible to

reverse the direction of running until the motor has come to a halt.

Motor brake mode

If the jumper is removed, the power stage works in 4-quadrant mode. The motor is still fed pulses of varying length corresponding to the

throttle stick position (pulse frequency still 16 KHz). However, the motor is short-circuited momentarily between the individual pulses and

also at neutral. The motor now acts as a brake, i.e. braking occurs when you reduce the throttle setting, and is proportional to the stick

position (active braking). At the same time the braking energy is fed back into the battery (caution if using a mains PSU!). In this mode

the direction of running can be reversed at any time. The brake light is not active.

Auxiliary functions

Multi controllers feature additional sockets for brake light and reversing light. These are de-coupled galvanically from the controller

electronics (opto-coupler) and can thus be used independently of the power circuit. If activated, the Brake and Reversing light sockets

are connected to COMMON. Note that the maximum switched voltage is 25 V, the maximum switched current 5 mA. This is sufficient for

operating normal LEDs, including several wired in series. If you wish to use filament bulbs or super-bright LEDs you will require a switch

amplifier.