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Pololu RC Servo 4 Ch Multiplexer (part kit) - Part No: 3401-020
Shipping Weight 0.005 Kg

This compact device serves as a four-channel multiplexer of hobby radio control pulses, allowing easy switching between two independent signal sources. A fifth channel selects whether the output is from the master or the slave source: a pulse width below the threshold selects the master channels, while a longer pulse width selects the slave channels. This version is a partial kit.

The Pololu RC servo multiplexer can be used with standard hobby radio control systems and servo controllers to allow easy switching of servo control between two independent sources using a fifth channel as the output selector. This makes it ideal for applications in which you have two possible control sources and want to be able to switch between them on the fly. For example, you could connect two RC receivers to the same set of servos (or similar devices, such as RC-based motor controllers) and allow the master transmitter to decide whether the master or slave transmitter is in control, thereby setting up your own buddy-system training setup. Another possible application would involve multiplexing between an RC receiver and a servo controller, which would allow you to switch between autonomous and manual control of a set of servos.

The pins on the multiplexer allow for easy connecting to servo cables: the column along the outside edge of the board is ground, the column in the middle is power (which must be supplied by the master), and the interior column is the signal. The pin spacing is 0.100". The male headers can be used with standard servo connectors; the kit provides additional flexibility and compacteness by allowing wires to be soldered directly to the board, as shown in the picture to the right. This kit ships with three 13×1 male header strips, a 2×1 male header strip, and a blue shorting block.

The power supplied by the master should be between 2.5 and 15 V, and it must be capable of supplying the current that the servos connected to the outputs draw. The logic voltage used on the multiplexer board will be regulated to 5 V if the supply voltage is greater than 5 V; otherwise, it will be approximately equal to the supply voltage. Note that the master and slave signal voltages must not exceed this logic voltage.

Pins S1 through S4 comprise the four slave input signals and pins M1 through M4 comprise the four master input signals. Pins OUT1 through OUT4 are the multiplexed outputs, and their source is determined by the signal on the SEL pin. If the selection pulse width is below the 1.6 ms threshold, OUT1 through OUT4 output the signals on M1 through M4, respectively (i.e. the master source is output); otherwise, OUT1 through OUT4 output the signals on S1 through S4, respectively (i.e. the slave source is output). Note that there is approximately ±0.1 ms of hysteresis on the threshold, meaning that the pulse width will have to get to approximately 1.7 ms before the slave signals become the output, and once this happens, the signal will have to fall below 1.5 ms before the master signals become the output.

If the selection signal is invalid, an optional jumper across the pins labeled J1 determines the output behavior. If the jumper is left off, the output channels go low and stay low for as long as the signal on the SEL pin remains invalid. For many servos and electronic speed controls (ESCs), a constant low on the signal line will turn them off, which might be desirable if the control signals are known to be bad. If the jumper is in place, the output channels default to the master signals if the selection signal becomes invalid. The multiplexer considers a valid RC signal to have a 10 – 100 Hz pulse rate and a 0.5 – 2.5 ms pulse width.

Indicator LEDs

The board has three indicator LEDs. If the outputs come from the master, only the green LED will be lit; if the outputs come from the slave, the yellow LED will be lit; if the outputs are turned off (all low) because of an invalid selector signal, the red and green LEDs will be lit.

Quantity Price per Item (info)

1+ £15.80 (Including VAT at 17.5%)
£13.45 excl VAT

This site is closed to new orders but this and over 5,000 other products can be ordered from our superb new website at technobotsonline.com

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Pot Servo Controller - Part No: 3403-010
Shipping Weight 0.020 Kg

Control a servo using a variable resistor (potentiometer). As you turn the pot, the servo will track the pot movement. You could also use it to control the input to a RC input motor speed controller (i.e. Electronize range). Supplied complete with a 10k pot, interface, leads and a battery connector that will fit our AA battery holders (not included) and instructions. Requires a 6V supply.

You can even use a pair of switches and a couple of resistors to drive the servo to preset positions. Using a pot of a value other than 10k will change the overall angle of rotation. Other inputs with a little imagination could be light control using LDR's (see our opto section), temperature control using thermistors etc..

Quantity Price per Item (info)

1+ £4.49 (Including VAT at 17.5%)
£3.82 excl VAT

10+ £3.82 (Including VAT at 17.5%)
£3.25 excl VAT

This site is closed to new orders but this and over 5,000 other products can be ordered from our superb new website at technobotsonline.com

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Servo Position Controller Kit - Part No: 3403-015
Shipping Weight 0.050 Kg

Another project designed by Alan Bond of the Solent Radio Control Model Boat Club This module was developed for the control of servo operated guns and cranes mounted on the decks of model boats, but aircraft, military and robotics modellers etc will doubtless find other applications for it. It combines the functionality of an R/C switch, a servo-slower and a servo stretcher in a single unit not much larger than a standard servo. See the video below to see the servo controller in action.

The R/C switch function detects joystick positions either side of a centre deadband and sets the servo moving in the appropriate direction. Releasing the stick (to centre) at any time stops the movement and holds the servo position achieved. The end of travel limits for port and starboard can be individually set by the user. Also, if the servo can cope with being (mechanically) over-driven, the usual +/- 45 degrees of available swing can be extended up to a full +/- 90 degrees, thereby avoiding having to gear up the servo shaft to achieve such an angle of rotation - this solution is also free of the backlash and jerkiness associated with gearing or chain drive. The traverse rate of the servo can be set to take from approximately 2 to 30 seconds from end-to-end (180 degree swing)

Click on the data sheet button below to open the assembly instructions. For the technically minded, a pdf of the source code can also be viewed below.

The kit is includes all parts, colour assembly booklet including and a programmed PICAXE chip but excludes the optional case. The kit is assembled on stripboard rather than a ready made PCB which helps keep the cost low.

Quantity Price per Item (info)

1+ £8.12 (Including VAT at 17.5%)
£6.91 excl VAT

This site is closed to new orders but this and over 5,000 other products can be ordered from our superb new website at technobotsonline.com

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Video of the Alan Bond Servo Controller in action

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