Wireless circuit for rotating geared motor in loft ?

[Jolly 7]

I was wondering if it is possible to rotate a geared motor both clock and anticlockwise in small steps using infrared or radio frequency. I have a motor but need to buy or build a suitable controller for this purpose. Any suggestions please ?

[Radio Wrangler]

You're still going to have to wire some power to it anyway. Small antenna rotors crop up at amateur radio rallies quite cheaply. It's the larger ones which fetch big bucks.

Infra-red isn't going to work unless the floors and ceilings between you and it are transparent!

David

[Jolly 7]

Thanks David. The motor is 12V DC high torque for rotating a lightweight plastic frame antenna. I was hoping to power it from the loft itself and just use one downlead for the signal feed.

[David G4EBT]

Ordinarily, rotators work on the bridge principle. There's a potentiometer in the control unit and another one in the rotator. When the bridge is balanced, no current will flow to the motor, but when the controller knob is moved to a different compass point, it unbalances the bridge powers up the motor till the bridge comes into balance. A simple idea proven over many decades.

My first homebrew rotator was for a 2M loft aerial and consisted of an ex WD aileron motor of an aircraft which worked on 12V. I had micro-switches at the end of travel in each direction which changed the polarity to reverse the motor. For a direction indicator, I glued eight glass reed switches to the inside of a short piece of plastic drain pipe, slid over the rotator shaft. A magnet on the shaft operated the reed switches as it passed each compass point, a series of resistors were brought into circuit. The chain of resistors were in series with a 1mA meter, which caused the meter needle to move progressively back or forth across the scale, which I calibrated at the various compass points.

I probably got the idea of Tony Hancock, or someone cut from similar cloth!

I can't see that you could easily operate a rotator wirelessly, but you can be sure that someone has done it, if only for devilment.

One possibility would be to use a digital proportional model boat transmitter/receiver to operate a servo in the loft, but of course a standard modellers' servo wouldn't be powerful enough to turn an aerial shaft.

Good luck in your endeavours.

I use a high torque RC servo (at the end of the garden) to rotate my 1m Wellbook loop, easy to control with a variable pulse length (1 to 2 ms).

[dseymo1]

I appreciate that you already have a motor, but a stepper motor would be the obvious choice here. You can buy remote controlled driver modules for them for next to nothing.

[TrevorG3VLF]

You will have a cable to connect the aerial to the receiver. DC voltage piggy backed on this could drive the motor in either direction.
To add feedback as well woud need some thought.

[Jolly 7]

I did think about combining the aerial downlead and DC power supply but am worried that the DC voltage might damage my receiver when plugged into the aerial socket. The receiver in question is a Sangean ATS909X and I have heard its front end is prone to static damage.

[G6Tanuki]

There is a widely-used (for the last 20 years or so) protocol/standard for this - it's generally used for 'steerable' satellite-dishes.

Motor-power- and positioning-info go up the coax.

See https://en.wikipedia.org/wiki/DiSEqC


Not "Wireless" but it does mean you don't need any local power at the head-end.

[TrevorG3VLF]

A capacitor at each end of the cable will allow the signals through but stop DC. The DC is added to the cable through chokes.
To give protection to the radio, place a couple of diodes (1N4148) across the aerial input.

An amplifier to match the aerial to the 50 ohm cable may help.

[Jolly 7]

Originally Posted by G6Tanuki

There is a widely-used (for the last 20 years or so) protocol/standard for this - it's generally used for 'steerable' satellite-dishes.

I am familiar with this setup. In fact I have a motorised satellite dish where the LNB and motor are supplied with 12V DC from the satellite receiver. One of my previous satellite boxes didn't take kindly to an accidental short circuit caused by a single loose strand of coax shield and got damaged.

[Jolly 7]

Originally Posted by TrevorG3VLF

A capacitor at each end of the cable will allow the signals through but stop DC. The DC is added to the cable through chokes.
To give protection to the radio, place a couple of diodes (1N4148) across the aerial input.

Thanks Trevor. Would 0.1uF be suitable to stop the DC, one from the central conductor and one from the shield to the radio input jack ?

[Biggles]

0.1 would be a bit on the big side. Maybe 100-470pF? It depends on what frequency bands you are trying to receive really.

[Jolly 7]

Only MW and SW.

[TrevorG3VLF]

The capacitor is not critical and you do not need one in the screen.

[emeritus]

I built a rotator for my FM dipole with the feed arrangement as per #10 in the late 1970's but with no amplifier or protection diodes, using a low voltage geared motor (Swiss) from Proops. The coax was connected to the dipole via 2 loose turns to allow somewhat more than 360 deg rotation, and I used two micro switches to limit the rotation in both directions, with diodes connected across the contacts to allow rotation in the opposite direction after the limit had been reached. I used a centre-off, spring biassed to OFF, DPDT switch to select rotation in the desired direction. I used to use the deep null of a horizontal dipole to null out local transmitters to listen to continental FM stations, usually with enough signal to receive in stereo. It was only necessary to rotate until the unwanted signal was reduced, so I didn't need to know what the bearing was. It worked OK, but when the FM band started filling up with commercial and local radio stations, receiving European stations was no longer practical, so I stopped using it.