IBCrazy's DIY antenna tracker!!! - Page 16 - RC Groups
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Jan 31, 2013, 08:42 AM
Engineer for Christ
IBCrazy's Avatar
^Possibly, but the helical antenna has side lobes that could be problematic. It would be better to use a crosshair due to lack of sidelobes.
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Jan 31, 2013, 10:06 AM
Registered User
Ok. Perhaps it's time to solder some components and test then. Just a bump if it doesn't.
Feb 03, 2013, 08:42 AM
GoThe Distance
ok it tracks east and west, but what about north and south??? If you have an antenna with a beam of say 30 degrees you are going to have to pan up and down at some point
Feb 03, 2013, 10:02 AM
Registered User
If it tracks east and west it will also cover north and south with just pan. I don't understand what you mean here? It can't track up and down at the same time since the lowest RSSI value is the preferable antenna.

Originally Posted by A914freak
"ok it tracks east and west, but what about north and south???"
Feb 18, 2013, 08:18 AM
Registered User
Leszek_K's Avatar
Did the first successful flight with my tracker. Video on 5.8GHz, 3 x 5 turns helical antennas. Tracking antennas set at about 30 degrees angle. All controlled by PIC16F688. It compares RSSI from 2 305 modules and drives a servo. Servo with removed stops, pot disconnected from a drive and set to center. So - pulse shorter then 1.5ms moves it to the right, loner - to the left, no pulse = no movement. Very simple circuit, very little wiring, all intelligence in a software.
Downside of using A/D converters - as modules are always slightly different and RSSI drifts with temperature, rx modules need to be left on for about 20 minutes till RSSI stabilizes and system can be calibrated. But - it tracks perfectly up to the very end of video range. It looses a track with model nearly overhead, as expected.
Feb 24, 2013, 02:08 PM
Ground successfully attacked!
GroundAttack's Avatar

Would this work

Firstly, thank you Alex for sharing this and all the antenna information so freely with everyone.

I am considering making something similar for 5.8G but basing it on Arduino, reading the RSSI from two crosshairs and using a helical for the video central channel, maybe even expanding with two more antennas for up/down.

I am hoping to use these modules as they are so cheap. Any advice welcome.
Feb 25, 2013, 01:06 AM
Registered User
Wow, those are cheap! Perhaps it's time to build one now when the Rx is in that price range!

I'm interesting in how the tilt will work for you "GroundAttack"
Mar 13, 2013, 03:19 PM
Registered User
Q: Will you build one for me?
A: No. But I will sell you all of the parts

how mutch for all the parts:
1 Standard size servo (the slower and deeper gearing, the better)
2 standard RX units 900 mgz
2 1N4148 Diode
1 TO-220 heatsink
1 - uA 7805 voltage regulator
1 LM393 voltage comparator
1 LM358 OpAmp
2 555 timer (NE555N or similar Optionally, you can use a single 556 timer as well)
1 1 MegOhm potentiometer

could you send it to me please?
Mar 14, 2013, 12:06 PM
Engineer for Christ
IBCrazy's Avatar
^I don't have the servos or the receivers, but I do have the rest of the parts. PM me with your address.

Mar 23, 2013, 03:43 PM
Registered User

I am actually through your all the design information for this tracker(its really awesome) .Finally i decided to use your design for my academic project purpose to track an 900MHz frequency via rectenna as input instead of any Rx modeule.

But I have a lot query .hope you will answer
1) In modifying servo you mention to connect/solder the extra wire to center pin of servo.(whats that center pin actually ) even after removing the POT the original center wire is as it is then where this extra center wire going to connect.
as the motor inside servo having three pin do i need to connect that voltage position control pin to one of those wire. (pls explain this point well)

2) why you are using two 555 is that to form H- bridge.
3)Please explain how the servo move bidirectional as i am not getting it well.

Mar 25, 2013, 11:12 AM
Engineer for Christ
IBCrazy's Avatar
I'm not using the 555's as an H-brige. I am using them to set a pulse for the tracker to adjust. The servo needs a PWM input. I used two 555's because it was easy. They are set at different pulse widths to tell the servo which way to move according to the RSSI numbers.

The center pin of the servo is the position indicator. Inside the servo is an A/D converter that converts this to a position. In removing the POT, the servo losses position. The resistors tell the servo that it is always centered and thus, when the pulse comse in to move one way or another, the servo simply moves that direction. Since there is no direct connected center, the servo instead moves indefinitely until the tracker is centered when the RSSI numbers match. The second 555 is to control oscillation since the tracker tends to overshoot.
Mar 26, 2013, 04:13 PM
Registered User
Thanx for your reply,

Now i actually understand :
The first 555 is triggering second at interval adjusted by pot while the second 555 is generating PWM.

Again when i trace the output of the second 555 in circuit i found that at default its giving ON time og nearly 0.4msec while OFF time of 5ms made servo move anticlock wise.

So if the servo moves with varying PULSE WIDTH then how it controlling servo direction by extra pin attached to center of removed POT from an servo ?

I am actually not able to control (move servo bi-directionally) servo by applying 0-10 V (varied) at modified PIN (before using any comparator output)?

Now could you pls explain or tell how to made it work ?
Mar 26, 2013, 04:36 PM
Engineer for Christ
IBCrazy's Avatar
^You aren't varying the pulse width. You are varying the location of center position. The pulse you are giving it tells the servo to go to center. The RSSI numbers fed into the system tell it where center is.

Mar 27, 2013, 12:32 AM
Registered User
I am actually confused too much now.If possible will you please give me some reference/link that i can easily understand the way you are using PWM IN YOUR TRACKER.

Mar 27, 2013, 05:05 AM
Fidler & twidler
empeabee's Avatar
Originally Posted by polarizadmax
I am actually confused too much now.If possible will you please give me some reference/link that i can easily understand the way you are using PWM IN YOUR TRACKER.

I hope this is not too simple for you.
To control the position of a servo, you need to apply a PWM signal to the servo.
This signal should be approximately between 0.5 mSec and 1.5 mSec long centered on 1 mSec. The "normal" repetition rate is 60 per second.
When it is 1 mSec the servo will be in the centre, 0.5 mSec fully 'one' way, 1.5 mSec fully 'the other way'. Normally he servo compares thie width of the signal to the position of it's built in potentiometer, and stops moving when it has achieved a balance.
As I understand IBC's tracker, the potentiometer is removed, and the motion of the servo is controlled by his electronics, removing the need for horrible mechanical linkages.
I hope this helps, because this reply is "off the top", it is some time since I actually looked at his circuts and I might have it very wrong.
(just too lazy to re-read it all from the start again ).

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