Hello, I have many questions that i will attempt to order logically
Project Description: I want to make a long wire antenna for amateur radio use. This antenna will have a motorized feedline that will be used as the radiator of the antenna. By feeding out antenna line, I can theoretically make the antenna resonate on any frequency without an antenna tuner being necessary to match a non-resonant antenna line.
Questions:
What model of Arduino should I use for this?
It will have to drive a 12vdc motor
It will have to read how much antenna line is deployed
It will have to calculate whether to increase or decrease the antenna line deployed
I have read the threads that talk about measuring rope or wire coming off a spool which is close to this project, but this is different for a couple of reasons:
The SBC has to "know" how much wire is deployed when the system is turned on.
The SBC needs to calculate direction (in/out) of the antenna wire and the magnitude of that transition (how long to run the motor).
Any help would be greatly appreciated as this is my first SBC project.
The SBC has to "know" how much wire is deployed when the system is turned on.
The SBC needs to calculate direction (in/out) of the antenna wire and the magnitude of that transition (how long to run the motor).
Most Arduinos have EEPROM memory which will keep it's data even after power is turned off. So you just need to store the length of wire used in the last deployment in EPROM and the Arduino can read it the next time it is powered up.
If you have a formula for calculating the desired lenght you just program code to implement the formula. If the current length is 100ft and you formula computes 80ft then, 80 -100 = -20, so you know you need to reel in 20ft.
But you will only feed the antenna out one time, since you have no capability to reel it back in by your design. More work is needed! Why will the wire in the reel not also be part of the antenna?
Please try this yourself using manually operated components!
In the real world it is much easier to either: 1. attach multiple long wires to a single feed point,or 2. just use a simple antenna tuner and the longest wire possible.
Actually several of these antennas are in operation and it does deploy/secure the wire in and out of reels in the antenna box. Im just helping the inventor automate his design.
Without knowing the actual mechanical set-up I don't think I could give a reasonable suggestion on how to measure the wire length but doing what I suggested in post #2 should help with the code.
Whether your new controller can remember the previous wire length or not, there will be many cases where the controller must measure the wire length being fed out. Initial operation, program change, Power failure while moving the wire, probably others.
No Arduino can directly drive any type of motor. A driver circuit/chip/module is always needed. In your case, because you will need to pay out or reel in the wire, you need an "H-bridge" driver in order to run the motor in either direction.
An H-bridge can be a pair of ordinary SPDT relays. Or it can be a chip, or chip on a module, with no moving parts, and which can control the direction and speed of the motor, if that is needed for any reason.
Avoid L293 and L298 chips/modules. They are a very old design and much better modern alternatives are available. The choice of model depends on the current drawn by the motor.
Absolutely, I agree. My current challenge is figuring out a reference; a starting point. Once thats established, either from a "home" position or reading the EPROM, all deployment/secure transitions are simple math solutions.
I think ill need a quad encoder on the reels.
Is it possible to link 2 SBCs with a 200 ft LAN cable? If so, I think ill need 1 SBC in the antenna box to measure or meter antenna wire in and out, a 2nd SBC in the control box to send control signals to the 1st SBC.
You will need some kind of sensor to detect how many times a drum or pulley has rotated, maybe even partial rotations. Something involving a magnet and reed switch, or a magnet and hall effect sensor, or an IR sensor and some paint markings on the drum/pulley could work.
This does not need to be a quadrature encoder, I think. A quadrature encoder can not only detect how many rotations or partial rotations, but also in which direction. In your case, the Arduino will know the direction the motor is running anyway.
I think we need more detail from you to understand more about the possible sites for this sensor and how accurately it needs to work.
Alternatively, include some mechanism for measuring the resonant frequency of the antenna and extend/retract until the desired resonance is reached. The link in post #7 appears to simply be a remote controlled motor, with the length being adjusted manually (likely while using an SWR meter). US patent # US-7286100-B1 if you are really curious.
It would be helpful to have some mechanical setup to ensure even winding of the antenna onto the spools, otherwise you might get slight differences in the lengths of the two wires.
Make sure to provide ample RF shielding of the microprocessor and associated components.
But the transmitter must be putting out RF before and during the wire length changing. There will be multiple low SWR changes while while the wire is moving. Which SWR to chose from? Therefore lots of interference to others using the frequency.
Well, you know the frequency you want to use so you know the 1/4 wave length of wire needed and pay that out. We only need maybe 500 mW for a good SWR reading and that measurement only takes a fraction of a second. Then you change the wire length for minimum SWR say under 1.5:1. Then you can increase the power level. (This whole idea assumes that you have a good ground plane.)