Rotator Control how do I

[VK4TI]

Remember where I asked if the gear box had a shaft on one side and also on the other? From this you can connect a variable resistor that can turn the entire 360 degrees. Usually there will be a slight dead spot where it doesn't contact anything. Using a simple voltage feed to the variable resistor you can read the wiper arm voltage and equate it to the position of the antenna. You can use a positive voltage applied to one connection of the variable resistor and a negative voltage to the other connection on the variable resistor. With the right voltage levels you can read the degrees it is from north in a direct manner. This of course is not necessary and you could even use an ohmmeter to tell you where the antenna is pointed. Just make a small chart that shows the position verses the reading and you're ready to go.
Yes, you will need to get the RPM down to 1 RPM or so. Too fast and the intertia of the antenna will gradually start to wallow out the mounting for the rotator and that would be a problem. Too slow and you'll grow old before you get to the station you want.
Another thing you can do with the voltage feedback from the position variable resistor is to apply it to a voltage comparator and have that determine your permissable limits of travel. At "X" voltage the drive is disabled. Simple and makes the variable resistor even more versatile.
For speed you probably can use just a simple switch to apply voltage to the DC motor. A center off spring return SPDT switch will work really well. I would avoid using a straight switch because things happen sometimes and somehow the switch will be turned on and without mechanical limits or electronic shutdown limits the motor will run forever. The antenna might not turn but the motor will still be trying to get nowhere really slow and that would be a amature lock which means maximum current. This can burn up the motor. Makes the use of voltage comparators for limit setting sound even better, huh?
Okay that's all I have for now.
Good luck on your project.
73
Gary

Progress is being made , I found a 488 interface under the desk in a box so now I just have to finsh the interface between the 488 and the rotor , the rotor is fitted with a 10 turn 500 ohm pot which will offer about 550 degrees of turn before limiting , the motor being controlled by some 20 amp solid state switches in turn controlled through the 488 via some incomplete software written in visual basic , the 500 ohm pot interfaces through an a/d converter from the junk box into the 488 interface , I could have course bought a suitable controller for less than $180.00 but so far have spent about $50.00

[VK5TM]

Can you tell me where you got the motor and gearbox from please? (Unless it's a trade secret of course )

I have to get my VHF antenna up higher and also make it rotatable.

Glad to see it is progressing.

Terry VK5TM

[VK4TI]

Can you tell me where you got the motor and gearbox from please? (Unless it's a trade secret of course )

I have to get my VHF antenna up higher and also make it rotatable.

Glad to see it is progressing.

Terry VK5TM

Answered by pm

[AB9LZ]

I think there is a huge dollar value in the fun of making stuff thats hard to quantify. For me, a $50 investment in parts == abt a thousand bucks worth of fun.

If I had the same problem, I would have used an H bridge configuration with some big power transistors and a single home sensor (no need for a rotary encoder), the software would be simple to write, and you could do stuff like soft starts / stops, memories etc.

73 m/4


73 m/4

[VK4TI]

I think there is a huge dollar value in the fun of making stuff thats hard to quantify. For me, a $50 investment in parts == abt a thousand bucks worth of fun.

If I had the same problem, I would have used an H bridge configuration with some big power transistors and a single home sensor (no need for a rotary encoder), the software would be simple to write, and you could do stuff like soft starts / stops, memories etc.

73 m/4


73 m/4

I thought abought building a few things but when ebay is so cheap a simple ss/relay board for $7.00 seems the thing to do , the software is based on VK hams work and modified to suite , dead simple solution to a commercially expensive problem and still under budget and a few hours fiddling

[VK4TI]

I thought abought building a few things but when ebay is so cheap a simple ss/relay board for $7.00 seems the thing to do , the software is based on VK hams work and modified to suite , dead simple solution to a commercially expensive problem and still under budget and a few hours fiddling

I have based a simple workable controller without feed back on an artical in Practical Wireless 1977 off a 741 op amp which can be found here http://www.4shared.com/office/QDXaJ3...PE1977_1_.html
the relay board can be found on ebay for almost nothing and over all build cost is about $20.00 , we will in due course make the computer interface available for those who wish to roll thier own (one day)
B

[VK4TI]

I thought abought building a few things but when ebay is so cheap a simple ss/relay board for $7.00 seems the thing to do , the software is based on VK hams work and modified to suite , dead simple solution to a commercially expensive problem and still under budget and a few hours fiddling

I have based a simple workable controller without feed back on an artical in Practical Wireless 1977 off a 741 op amp which can be found here http://www.4shared.com/office/QDXaJ3...PE1977_1_.html
the relay board can be found on ebay for almost nothing and over all build cost is about $20.00 , we will in due course make the computer interface available for those who wish to roll thier own (one day)
B

[VK4TI]

The happiness to me has changed!

I hope this means you found good help here

[KH2G]

CDR system is simple an homebrewable. It is a wire wound resistor with the wiper stationary and the pot mounted on the moving bell top. You could set it up anyway you want so the wiper varies as the antenna turns. The pot is one side of a bridge with a meter across which was cal'd for compass direction. The servo just needs a double pole double throw resistor.
Have fun
Dick