Solent Radio Control Model Boat Club

Posted on Feb 7, 2014

A `servo slower` which has now evolved into a Servo Controller. `Servo slower` units are used to reduce the slew-rate (traverse time) of proportional servos. The most common use in model boats is to control the rotation of a servo-controlled gun turret, where trying to do so by transmitter stick movement alone results in unrealistically rapid and/or jerky motion.

Solent Radio Control Model Boat Club
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Using a `slower`, the stick can be thrust right or left and the servo will turn slowly and smoothly until it is aligned with the position commanded by the stick. The end to end travel time of the servo is adjustable in ten steps from `straight through` - ie the `slower` is inoperative - up to approximately 30 seconds. Actual times will vary dependent upon the transmitter frame rate. Connections are via a flying-lead to the receiver and pcb mounted connector to the servo. This unit is based on a `PICAXE` micro-controller so all the clever stuff is done in software and as a result the parts count is minimal. The photo shows a prototype unit built on the readily available PICAXE project board AXE021 and the circuit diagram reflects that situation. Should you wish to build the unit on strip-board then the 3. 5mm stereo jack socket (used to program the PIC over a serial link from your PC) can be omitted, together with the programming link LK1. If omitting the jack socket, R1 and R2 cannot be omitted - otherwise the serial input would `float` and the PICAXE could interpret that as a signal from the PC (which it expects to be attached to this input) to enter re-programming mode. R1 and R2 can of course be replaced by a single 33K resistor. The white-ish looking LED is in fact a red/green bi-colour device which flickers at the transmitter frame rate to show the unit is operating. It flickers green whilst the servo is in alignment...

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