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Gentlemen

I am in the process off putting all my electronics in my airframe and just wanted any comments just incase I am breaking any golden rules of electronics. I know I will more than likely strike noise problems and I am prepared to spend time working them out but I would like to start with a good base point to make the job easier.

Air frame Draganfly Predator

Speed 400 pusher at rear . The speed controller is going to be mounted about two inches from the electric motor. Then the battery will be mounted about one inch in front of the speed controller. Coming off the speed controller side off the battery connector will be another set off wires that goes to a PT5041N DC-DC boost regulator (All caps will be installed as per MR RC-CAM project). The PT5041N will sit opposite the speed controll about an inch away. The PT5041N will supply 12 volts to a camera TX. Parrallelled of the input side of the PT5041n will be the power heading to the front of the plane for the rest of the electronics.

The receiver is powered by the speed controller. I will be attempting to share the same power source for everthing.

I know that I am asking an almost imposible question but I would appreciate any comments.

Is it good practice to have the speed controller near the motor?

Will the PT5041N affect the speed contoller or vice versa?

Any advise appreciated.

Crash Pilot1

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Crash Pilot,

Although I have little experience of electric flying, no electric AV and I don't know the your aircraft(!) my view is that I would run the AV gear from a seperate supply. Because of the high capacity of AAA and AA cells these days you can get a very reasonable duration (depending on the load of course) from a small, lightweight 4.8V pack (ie 4 cells) and a DC-DC converter. Ahab assembled an AA 1800mAh pack with an integral converter and it works fine and gives more than adequate performance. He was driving a bullet cam and a video Tx. In my opinion you are far better off avoiding problems in the first place rather than trying to cure any symptoms. Therefore isolating one system from the other has to be the starting point.

With regard to motor power leads before and after the controller:

Keep them as short as possible, use high quality connectors and use the most substantial cable with the lowest resistance possible.

I am sure that the electric flyers amongst us will be able to offer you further advice.

Hope that helps

GL

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GL

Thanks for you response. The reason I want to share the flight battery is because I'm limited to space and weight is also a issue. I have alot of gear that I need to fit in. I will be cutting access panels in the body so that I can try and get the Center of gravity right. I will try to post a picture. The predator has a pod at the front were all the gear goes and the motor is at the back. In the front I will have GPS, Altitude hold PCB, Autopilot . Tinytrack SMT , MAHI. Receiver and Co-pilot , CCD camera and 2 sub micro servo's. In the body toward the back will be speed controller , Li Pol 7.2 V flight battery and camera transmitter. The transmitter will be sitting on top. If there is any room left in the centre body and the weight is O.K I was going to install a sony digital DSC-U20 (camman modified camera)

I have all the gear I just need to install it all. Everthing has been bench tested and works. I will be installing one piece of equipments at a time and sorting out the bugs before I install the next piece of equipment.

If others also think it is not a good idea to share the one flight pack I could possible forget the digital camera and use a LI ION pack that I have to power the rest of the gear.

Only problem is that I have to then monitor both packs because the autopilot will be powered by the camera TX battery because it requires 6volt or above and the BEC on the speed controller is only 5 volts. If the TX battery goes flat or fails It will lock out controll to the rudder(V tail) even when the autopilot is disarmed.

Crash Pilot1

post-8-1117630650_thumb.jpg

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This project is exactly what I hope to do someday. Keep us updated as to your progress! I'm very interested as to how it all comes together. Have you thought about using a 2s 640 or 900mah Li-Po with the Vreg to power all the electronics? That way, you would have eliminated any possible EFI noise traveling through the power wires and into your electronics, and these Li-Po's are very light, around 2 ounces. Good luck!

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philthyy

I have thought about it but space is an issue. I have started the setup and put things into place just incase I need to go this way. I will try one 2100 mha LI PO with a DC-DC switching boost regulator to drive everything for convenience. Before I fly I will be testing everything on a osc scope to see if I can see any noise.

I have cut a panel in the rear of the body and installed the battery there. Buried under the battery is the boost reg. If I have problems I have allowed room to remove the boost reg and install a second pack.

The battery , Boost Reg , Speed controller , Camera TX and motor will all be at the rear which will allow the front pod to be clear for the rest of my gear. This should balance everything out O.K with the CG.

This model says it can carry a payload of 16 ounces but the only space is in the front POD which would make it way too nose heavy.

This plane is a nice looking plane but no way is it worth the price tag.

I will keep you posted on my progress.

Crash Pilot 1

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Before I fly I will be testing everything on a osc scope to see if I can see any noise.

If you are sharing the battery with the motor then the commutating ripple will be easily measured by the scope. But it is unlikely you will see any EMI/RFI noise with the o-scope. The R/C system will show you it if it exists, so the scope is not needed for that.

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Mr RC-Cam

I have built the glitch counter project that you have designed so I will use that to try and aid me in my quest. I will also rely on monitoring with range checks as I add components.

I know you probably dis-approve of using the same power source but it makes things easier if I can get it to work.

The other reason is that if I do strike problems it will really improve my knowledge trying different thing to sort out the problems. So I hope I can gain alot of knowledge from trying this.

In the event that I feel I am not 100% satisfied that i can't get the system reliable I will revert to a separate pack.

Question

By using DC - DC switching regulators arn't we isolating the power supply anyway. This should eliminatate the ripple effect but the RF will be present regardless if we use separate packs or not. Isn't RF airbourne noise. The only problem I can think of that I am adding is the noise from the DC-DC switching reg.

I don't know if this is correct but if someone could confirm it would be great.

I really want to understand and improve my knowledge so please be patient.

Thanks

Crash Pilot1

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Mr RC-Cam

But it is unlikely you will see any EMI/RFI noise with the o-scope.

I have a Hioki power monitor.

In the past I had a air bourne noise problem and hooked the scope up to the battery connection on the RX across the signal and ground. It showed the PCM wave on the scope and everytime I introduced the noise I could see the wave change and become really spiky and erratic. I then checked across power to ground and there was no problem.

What am I measuring by doing this? Was that RF noise I was measuring in the past ?

Crash Pilot1

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By using DC - DC switching regulators arn't we isolating the power supply anyway.

Common DC-DC supplies do not provide conductive noise isolation.

Also, their transient response specs might not well suited for the fast rise time power spikes seen in our app. So really bad situations may need some extra filtering to work well.

This should eliminatate the ripple effect but the RF will be present regardless if we use separate packs or not. Isn't RF airbourne noise.

EMI/RFI can be conductive or radiated. Sometimes it is both.

It showed the PCM wave on the scope and everytime I introduced the noise I could see the wave change and become really spiky and erratic. ... What am I measuring by doing this? Was that RF noise I was measuring in the past ?

The noise source was affecting the Rx's PWM pulse, which is what your scope was observing. It wasn't measuring EMI/RFI noise -- instead it was monitoring the effects of the noise. It is rare to see typical EMI/RFI on a scope; It tends to be very broadband and very low level.

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