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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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19th Jul 2018, 3:35 pm | #1 |
Octode
Join Date: Feb 2018
Location: Southampton, Hampshire, UK.
Posts: 1,061
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Wireless circuit for rotating geared motor in loft ?
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 ?
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19th Jul 2018, 3:44 pm | #2 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Re: Wireless circuit for rotating geared motor in loft ?
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
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19th Jul 2018, 3:54 pm | #3 |
Octode
Join Date: Feb 2018
Location: Southampton, Hampshire, UK.
Posts: 1,061
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Re: Wireless circuit for rotating geared motor in loft ?
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.
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19th Jul 2018, 5:34 pm | #4 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,761
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Re: Wireless circuit for rotating geared motor in loft ?
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.
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19th Jul 2018, 7:36 pm | #5 |
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Re: Wireless circuit for rotating geared motor in loft ?
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).
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19th Jul 2018, 7:43 pm | #6 |
Retired Dormant Member
Join Date: Dec 2007
Location: Shropshire, UK.
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Re: Wireless circuit for rotating geared motor in loft ?
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.
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20th Jul 2018, 12:14 am | #7 |
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Re: Wireless circuit for rotating geared motor in loft ?
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. |
21st Jul 2018, 12:46 am | #8 |
Octode
Join Date: Feb 2018
Location: Southampton, Hampshire, UK.
Posts: 1,061
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Re: Wireless circuit for rotating geared motor in loft ?
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.
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21st Jul 2018, 8:44 am | #9 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
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Re: Wireless circuit for rotating geared motor in loft ?
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. |
21st Jul 2018, 11:26 am | #10 |
Rest in Peace
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
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Re: Wireless circuit for rotating geared motor in loft ?
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. |
21st Jul 2018, 12:02 pm | #11 |
Octode
Join Date: Feb 2018
Location: Southampton, Hampshire, UK.
Posts: 1,061
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Re: Wireless circuit for rotating geared motor in loft ?
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.
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21st Jul 2018, 12:08 pm | #12 |
Octode
Join Date: Feb 2018
Location: Southampton, Hampshire, UK.
Posts: 1,061
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Re: Wireless circuit for rotating geared motor in loft ?
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 ?
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21st Jul 2018, 12:19 pm | #13 |
Rest in Peace
Join Date: Feb 2004
Location: Hexham, Northumberland, UK.
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Re: Wireless circuit for rotating geared motor in loft ?
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.
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21st Jul 2018, 1:07 pm | #14 |
Octode
Join Date: Feb 2018
Location: Southampton, Hampshire, UK.
Posts: 1,061
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Re: Wireless circuit for rotating geared motor in loft ?
Only MW and SW.
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21st Jul 2018, 9:36 pm | #15 |
Rest in Peace
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
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Re: Wireless circuit for rotating geared motor in loft ?
The capacitor is not critical and you do not need one in the screen.
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21st Jul 2018, 10:48 pm | #16 |
Dekatron
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
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Re: Wireless circuit for rotating geared motor in loft ?
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.
Last edited by emeritus; 21st Jul 2018 at 11:01 pm. |