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Electric Stunt => Gettin all AMP'ed up! => Topic started by: tom hampshire on March 17, 2012, 03:12:59 PM
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Say Dean... One of our flying buddies wears a pacemaker. So if he launches an E stunt machine at nominal 20 volts, 50 amp, 13khz pulse rate, and around 6-700 watts, is there any danger of EM interference causing the pacemaker to miss?
A little searching turns up a 10 gauss limit on magnetic fields, with 1-4 kv/m for electric fields. See http://www.wiganleigh.nhs.uk/Internet/Specialties/Cardiology/pacemaker_faq.asp for some practical tips for pacemaker wearers. It turns out that nearly all household appliances are OK. Industrial hygiene guys limit access to electric machinery emitting more than 5 gauss. Chainsaws and trimmers held close to the chest are prohibited. Snow blowers and lawn mowers are Ok as long as the user doesn't get near the ignition system of a running engine. All current pacemakers are now shielded from new.
An RC groups search turns up nothing. My SWA guess is that the fields from our systems are too small to be of much risk. Are we safe to allow pacemaker patients to use/launch electric airplanes?
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Hi Tom, my wife has a pacemaker, and she often launches my electric models. I reckon she would feel it if there was any effect. I know that when she goes for a checkup and they fool around with the unit, she feels it immediately. I reckon that it's far enough away from the motor when launching, so I don't think that there is any problem. These units are really amazing and I know that they are well screened.
Keith R
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Ya, I have a freind that has a pacemaker so I asked him how long the battery lasted on that unit and he said ten to twelve years so I told him if they would put solar cells on that bald spot of his the battery might last longer. He really got5 charged up on that one! HB~> HB~> HB~>
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Hi Tom,
I'm glad some folks had helpful answers!
I had no idea, but I do have an old flying buddy who inadvertantly reprogrammed his heart rhythms by electrocuting himself on an automotive MSD (multiple spark discharhe) unit. He was hollering for most of a minute 'till his son came outside and shut off the still running car. (box Nova and big block for those who care!)
He has since been re-shocked and treated for short periods of time with external pacemakers to teach his heart the correct firing order.
Yikes!
Dean
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Hey Dean - It looks like proximity is the risk trigger. As long as the helper stays aft of the wing and SC, it's probably safe enough. HOWEVER, I did email Castle about it and got no response at all. If you talk things over with the powers that be, it might be a good idea to apply a gentle nudge in the direction of safety. Best, Tom
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Of course you got no answer!
Their marketing director is an attorney too! ;-))
Dean
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The magnetic field strength is strongest inside the motor. The magnetic path is almost completely closed so that little, if any, magnetic force (lines) exist away from a running motor. Wiring carrying heavy currents also have a magnetic field encircling the wire. But a wire represents only one turn of an electromagnet, so the inductive field is again slight.
Magnetic field strength is attenuated by the square of distance. Even if strong adjacent to the source, the field strength becomes insignificant more than a few inches away.
F.C.
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I have the spec sheets on EMI as pertaining to Pacemakers. If I can find them, I will post them.
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Found them.