Control Issues

Post by **BeligerAnt** » Mon Nov 01, 2010 9:04 pm

Peter, I'm not sure the motors are really radiating at 2.4GHz (I suppose they could be, but very unlikely). Far more likely I think that the interference is getting into the decoding logic, and aslo into the servo control circuit.
Have you tried suppression capacitors right across the motor terminals?

Shakey · Post by **Shakey** » Mon Nov 01, 2010 10:08 pm

Thank you for taking a look at the robot it is good to know that it can be helped. The next step i was going to take was to put some supression capacitors on to see if that did anything to cure it.

@Beligerant, I don't know how the motors are interfering with the receiver but I found (at brighton) that the further the receiver moved away the less it would lose control. Not exactly sure what you mean by decoding logic, though i have an idea about it.

It also looks like another reason to redisgn the chassis! (not just because it can't self right).

Also on a mostly unrelated note my dad has begun building himself an antweight so that should be good.

razerdave · Post by **razerdave** » Mon Nov 01, 2010 10:17 pm

I noticed a problem with my replacement option D board that the motor underneath the flipper servo (a HS-82mg, funnily enough) span when I activated the flipper, which may be related to this same problem you guys were having.

Side Note: Any idea what's stopped my old one working ? That one never did the servo/motor spaz out thing)

Post by **BeligerAnt** » Mon Nov 01, 2010 10:53 pm

@Haywire: The receiver includes some logic circuits to decode the pulse train sent from the transmitter into individual pulses for each servo channel. There are various descriptions of this on the internet, but some of them are not quite right! Anyway, on the 40MHz receivers I have looked at in detail the logic is pretty crude and prone to getting confused by extra pulses caused by noise picked up from (e.g.) motors.
Although the 2.4GHz radio is unlikely to be directly affected by the motors, the logic is probably still susceptible.

In cases of interference (or EMC - electromagnetic compatibility, or rather incompatibility

) distance is always your friend. Radiated energy decreases as the square of the distance, so doubling the distance between motors and receiver reduces the interference seen by the receiver by a factor of 4. Unfortunately there are no large distances in antweights, so there's a limit to what can be achieved.

Motors are notorious for generating interference. Suppression capacitors RIGHT ON THE MOTOR TERMINALS may help. Keeping the motor leads as short as possible and away from everything else will also help a lot. Keeping the sensitive bits (probably the receiver) away from the noisy bits (motors, including servos) also helps.

peterwaller · Post by **peterwaller** » Tue Nov 02, 2010 11:49 am

Gary I think you are right it is unlikly the interferece is any where near the 2.4 GHz frequency but some of the other stages. I haven't tried the decoupling across the motors as I cant seem to get the wheels off and the motors out but it seems ok now any way but it is always a good thing to try.
Dave I doubt the problem is with the replacement option D board but just general interference problems associated with 40Mhz receivers. As to your old unit it seems to be working perfectly certainly both motor drives work correctly. I will do some more testing but I think the fault must have been some where else.
Josh found I think it was a battery wire broken and I checked out the controller as I am updateing the firmware to mixing and it seems fine.
The only controller that appears to have failed is Jon's where apparently the two motors terminals were shorted to those on the other motor and that took out the drive chip. I have replaced that and it appears to be working but as he is now having problems with the replacement I need to look into that further.

Shakey · Post by **Shakey** » Tue Nov 02, 2010 12:58 pm

To get assailants wheels off just remove the tyres on them and there should be grub screws you can undo. There is also an amount of superglue, thatn should break easily, though they may take a bit of force. I don't mind re-glueing them.

peterwaller · Post by **peterwaller** » Tue Nov 02, 2010 2:36 pm

It is all working now so I don't really want to strip it all down again. To make a bit of space for the re-arranged gear I have also shortened the wires between the receiver and controller removing two of the red and black wires so you now have one plug with the three white signal wires and one with the single black and red. That and some shorter screws holding the servo in you will find it is about 5 gms lighter. You will need to re-bind the receiver to your transmitter when you get it back. If you can PM your address and if anyone is likely to be in to sign for it I will find some packing material and send it back.

Shakey · Post by **Shakey** » Tue Nov 02, 2010 4:50 pm

No problem, and also its good it has saved some weight now. There should always be some one in to sign for it and I will PM you my adress shortly.

razerdave · Post by **razerdave** » Tue Nov 02, 2010 8:02 pm

Pete: Because of the trim issue with the new board, would I be able to trade you the new one back for the old one ? I'll make sure it still works before I send you the new one back

peterwaller · Post by **peterwaller** » Wed Nov 03, 2010 8:18 am

Thats no problem I will do a little more testing to make sure its OK and then send it off and you can return the other when you have it all working.