Gyro bypass circuit required

[RogWarTheOAP]

Hi Guys,
I've installed a GY240 gyro in a DR1 triplane in the rudder circuit to stop the ground looping that seems to be almost inevitable with this particular aircraft. :mad:
The Gyro has a switch to use it either as a rate gyro or heading hold. I'm not sure which way I'll use it yet (suggestions?) but whichever way it's used I'll want to switch it off once the 'plane's in the air. So I've got to come up with a circuit which uses another channel to switch the rudder servo from using the gyro output to using the Rx output.
I'll come up with something in time but I don't have time to do it quickly and there's no point in reinventing the wheel - so does anybody have a schematic for anything similar???
Thanks in advance for any help/pointers/links etc
Cheers The OAP

[sesat]

Easiest is to use a gyro with a second input channel for gain.

Ram.

[Miami Mike]

How about this? Get one of these...

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCJD6&P=0

http://www2.gpmd.com/image/e/emom1010.jpg

and one of these...

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F011%5F002%5F013%5F000&product%5Fid=275%2D240

http://www.radioshack.com/images/ProductCatalog/ProductImage/275/275-240.jpg

Leave the +5 volt and ground connections like they are and hook up the control wire like this:

http://www.vvsss.com/ezone/gyro_switch.gif

[jeffs555]

Here is a link to a simple R/C switch. http://www.uoguelph.ca/~antoon/gadgets/rc-sw3.html To use it to switch from one of two servo signals, you shouldn't need a relay, replacing R3 and Q1 with another 4011 wired like this should work.

[Miami Mike]

I dreamed a similar circuit up last night using NAND gates instead of NOR gates and the PC board from a stripped out servo. I'll post more about it if RogWarTheOAP is interested. This project will be a trade-off between expense, weight, bench work requried, and skill required, so it's up to him to choose.

[Miami Mike]

By the way Jeff, a 4011 has NAND gates but your circuit shows NOR gates. Your circuit would use a 4001.

[RogWarTheOAP]

Sesat: If I had one of those gyro's I'ld have used it. :(

Miami Mike: I don't think I'ld trust a relay contact's reliability, especially if it gets vibrated. :eek:

Jeff555: & Miami MIke: - Yes that's the sort of thing I'm looking for. :) Mike I'ld be interested in your idea of using a servo PCB (I've got a collection of servo's with dodgy motors/gears etc). Please post details of your idea.

Thanks for your suggestions guys.
:D

[ElectoPete]

Hi

Try this:
http://corsair.flugmodellbau.de/files/elektron/GY240UMB.PDF

It turns your GY-240 into a GY-401 (with remote gain control)
OK - it is in German - but try a Babel Fish translation!

Pete

[RogWarTheOAP]

ElectoPete:

Thanks for a very interesting link - Any idea how to translate the German from a PDF? I can't highlight the text and drag it and my chances of typing it 100% correct are approx 0% :confused:
Cheers The OAP

[imodel]

If the gyro has the ability to be used as a rate (non-heading hold) and as heading hold, the gyro can be plugged into an aux. channel (assuming your receiver is capable) and the gain for onne of the rates can be set to zero. This in effect disables one the the gyros rates.

[ElectoPete]

The OAP

Here is a straight electronic translation of the text.

You have to convert it to "understandable" English. :)

Pete

[RogWarTheOAP]

ElectroPete:
Thanks for the translation. I like the idea and would love to try it. However, the trouble with being an OAP is that as you get older your hand starts to tremble. The amount of tremble is so slight you can't really see it but by the time it's magnified by the length of a soldering iron, the pointy bit is wavering about. It's only about 1/8th inch but that amount is enough to put me off soldering on SMD. It's hard enough with ordinary components. I don't want to knacker the gyro. :mad:

Imodel: The gyro rate/heading hold function is switched by a small switch in the casing not by another channel so that won't work I'm afraid :mad:


Cheers and thanks for all your suggestions: The OAP

[Miami Mike]

Mike I'ld be interested in your idea of using a servo PCB (I've got a collection of servo's with dodgy motors/gears etc). Please post details of your idea.Okay, but remember it's just an idea. I've never really tried this, but it seems to me that it ought to work fine.
Remove the PCB from the busted servo, leaving the harness attached. Disconnect the potentiometer and motor.
Wire two equal value 1/4 or 1/8 watt resistors in series and connect them in place of the potentiometer such that the PCB will "think" the servo is centered. Use resistor values that are half or more of the potentiometer resistance.
Build a circuit like Jeffs555 shows in post #4. You could use a 4011 chip with four NAND gates like he says in his text, or you could use a 4001 chip with four NOR gates like he shows in his schematic. The circuit will work either way. A Google search for "cmos 4001 (http://www.google.com/search?hl=en&q=cmos+4001&btnG=Google+Search)" or "cmos 4011 (http://www.google.com/search?hl=en&q=cmos+4011&btnG=Google+Search)" should get you all the pinout information you'll need. Although Jeff's schematic shows U1, U2, U3, and U4, you'll really need only one chip. (The gates should be labeled U1a, U1b, etc.)
Connect the lead labeled "from rc switch" to either empty motor terminal. Leave the other motor terminal unconnected.
Remember that the lead labeled "from rudder channel" also has to connect to the gyro input.
To build this as a separate module, I'd use two servo extension leads cut in half along with the existing harness attached to the salvaged servo PCB. You'll have a total of five cables to connect inside your plane, three of them male and two of them female.
It would probably be good practice to add a small capacitor from pin #14 (positive supply input) to pin #7 (ground) of the CMOS chip.

Good luck! I hope it works.

[RogWarTheOAP]

MIke:

I like it :o

Thanks for all your help guys - no further input needed unless you come up with something radical.
Cheers
The OAP

[Mr.RC-CAM]

http://www.delemarre.ciscon.nl/id70.htm

RC-CAM