High Voltage influence on a remote control

[pgk pgkParticipant @pgkpgk17461]

Many moons ago I worked at a clinic whose garden backed onto an overground section of the London Underground. It proved impossible to get clean ECG recordings from patient's laid parallel to the tracks but OK if they were perpendicular.

pgk

[SamsarandaParticipant @samsaranda]

Stuart, our A range is the one next to the power lines, the B range is well away from the cables and performs faultlessly. We had no problem with the old traps before the Laporte ones as they had cables connecting the control to the tower so no radio to be inferred with, but what a pain having to drag the cable around from stand to stand, not easy when the farmer allowed the grass to get long and tall for animal feed, can’t envisage going back to that.

Dave W

[Stuart Smith 5Participant @stuartsmith5]

From your initial post, it sounds like this problem has existed since the new equipment was installed.

Could it be that there is a fault with the equipment, not necessarily with the radio remote? Presumably you have contacted the supplier/manufacturer?

The presence of the overhead lines could well be a 'red herring',leading to assumptions that interference is the cause of the problem. As has already been said, the figures for field strengths etc are at the 50 hz power frequency.

[SamsarandaParticipant @samsaranda]

Stuart Smith S, thanks for your input, presume it is feasible that the problem is equipment related but it’s random occurrence has led us to suspect outside influence, difficult to quantify but the general feeling amongst our group is that the equipment is performing correctly, our thoughts are focussed to the proximity of the power lines, particularly after researching on the net how large a field high voltage power lines generate. You become only to aware of the current flowing through the lines on damp misty days when you can hear the lines crackling and humming.

Dave W

[SamsarandaParticipant @samsaranda]

PGK, your comment relating to the patients ECG and proximity to the underground illustrates how large the field of influence can be with high voltage cables and equipment, perhaps we should try laying our high tower horizontal instead of standing up to see if it helps, bit difficult to ensure a correct trajectory for the clays though, seriously perhaps a change of orientation of the receiving aerial could help in solving the problem.

Dave W

[John HaineParticipant @johnhaine32865]

I'be been giving some further thought to this.

1. The receiver in the trap on the tower must be integral to the trap? So it is hard to move it to a different place.
2. I assume the tower must be made of steel for strength?
3. The tower is ~20 feet from the power line (or 20ft high above ground?)
4. I've tried looking on both Google and OS maps, can't see any pylon runs in the vicinity of Pevensey though I'm sure there are some. Are they pylons or poles? Likely to be higher voltage if pylons.
5. The 50 Hz electric field strength at the top of the tower could be significantly greater than at ground level, because the tower is likely all at earth potential.
6. Radio devices can be affected by 50 Hz electric fields. I have observed this on my own VHF car radio as noted above and also in troubleshooting noise in a broadcast receiver system. Symptom of bad design.
7. One cannot rely on cheap modern electronic devices being designed to reject large fields at the input – RF skills are in short supply, often the designers just buy an off the shelf chip and follow the application circuit, and the interference case is most unusual! Not that they probably do much testing anyway – often the antennas are truly awful.
8. So we can't rule out sensitivity of the receiver to the 50 Hz electric field.

However, it should be easily possible to screen the unit from these fields if they are the problem. What you need is a horizontal conducting metal plate above the trap earthed to the top of the tower. At 50 Hz this will create a field-free zone between the plate and the top of the tower and so screen the receiver. As long as the gap between the plate and the receiver is a wavelength or so – ~75 cm – it should have little affect on the wanted RF (probably 433 MHz) . The plate could simply be a sheet of chicken wire on a wooden frame, I'd have thought a meter square – I assume that the trap chucks out sideways? Simple to do, could be worth a try.

[Stuart BridgerParticipant @stuartbridger82290]

I don't know Laporte traps, so the OP can provide further details. I have worked on Promatic and CCI traps.
Usually there is a socket on the trap where either a traditional cable release or the radio receiver plugs in. The cable release is simply an n/o push button switch on the end of a long wire. This will either bring the trigger( clay release) line from 0V to 12V or vice versa (Promatic and CCI work in opposite ways as I found out when getting a radio to work on a CCI). With the radio release the push button is replaced by a set of relay contacts driven by the radio. The release connection socket also provides a 12V supply to power the radio. So as long as the distance isn't too long, resulting in a volt drop on the radio power, relocating the receiver shouldn't be too big a deal.

[SamsarandaParticipant @samsaranda]

In respect of all those who ventured possible solutions to this thread concerning the random firing of one of our launchers on our skeet range I can now bring positive closure to this thread; the problem appeared to be getting worse so we contacted the manufacturer, Laporte, it transpired that a large number of launchers had been despatched with relays that were faulty. Laporte have now changed supplier of these relays and replacements are available FOC, they supplied us with two, one for each of our launchers that we purchased recently. The replacements were fitted two weeks ago and to date no problems have arisen. The new supplier of relays to Laporte for this particular item is Panasonic, hopefully their reputation for quality holds good. I like to ensure that I provide closure where I can on threads that I raise, and in this case it appears the high voltage cables were a red herring, anyway I would like to wish everyone a prosperous New Year.

Dave W

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